The Coastal Paleontologist returns

Snapshots from Paleocon 2026: a few days with friends and colleagues, fossil whales, and too many mastodons

2026-08-31T11:59:24.882-07:00

A couple of weeks ago Sarah and I spent three days in Hemet, California, attending our first 'PaleoCon' event at the Western Science Center. Hemet is a small suburban city in the easternmost part of the "Inland Empire", located about 20 miles northeast of Temecula, and about 25 miles southeast of Riverside/San Bernardino. Hemet is situated just below the formidable Mt. San Jacinto - the same enormous mountain you can see looking west from Palm Springs. In the mid 1990s, a new reservoir was being constructed at Diamond Valley. This valley is open at the west and east ends, and so two dams were needed to be built. During this project, a team of paleontologists led by Kathleen Springer and Eric Scott (then of the San Bernardino County Museum) ended up discovering a literal treasure trove of Pleistocene land mammals, including many skulls and partial skeletons of mastodons, mammoths, ground sloths, and many others. A new museum was funded and opened in 2006. My 'whaleontologist' colleague Dr. Alton Dooley Jr. was the curator at the Virginia Museum of Natural History, and in 2015, was brought on as the new director for the WSC. Shortly after arriving he realized that there were some stark morphological differences between "Max", the best preserved Diamond Valley mastodon specimen, and Mammut americanum specimens from the midwest and east coast. Dooley published an important monograph in 2019, naming "Max" as the holotype of the Pacific mastodon, Mammut pacificus, and reidentifying many dozens of west coast specimens to this new species.

Western Science Center has been hosting an event titled "PaleoCon" for a few years now, and we've attended two of them strictly as unofficial visitors, but this year, Sarah and I were invited to participate as visiting scientists. It's not an academic conference: if anything it feels more like paleontological summer camp. There are no scientific talks, and the days before the conference, we spend in the curation lab and collections room, looking at interesting specimens, getting ideas, and recording data. The summer camp vibe continued in the evening where we hung out in hotel rooms catching up, since we already happened to know most of the other attendees, many of whom are invited every year. Eric Scott, for example, who is now a mitigation paleontologist for Cogstone Resource Management - is a regular at this event (and for good reason, since he was a leader on the original excavation). Also in attendance was our longtime friend Brian Beatty from NYIT - Brian is another marine mammal paleontologist, and was a coauthor on our papers on Coronodon and Ankylorhiza. Both of "Mels" were present - Melissa Pardi from the Illinois State Museum, and mitigation paleontologist and giant ground sloth expert Melissa Macias (Duke CRM). Another sloth expert and mitigation paleontologist, Ascanio Rincon (Cogstone RM) was here this year, studying sloths. Meaghan Weatherell, an artiodactyl paleontologist, and Win McLaughin (who has worked on rhinos, artiodactyls, and walruses) who were grad students together at University of Oregon were also in attendance. Though our colleague Katy Smith, a mastodon expert from Georgia Southern University, was not present this year, her GSU colleague Christina Olson returned as the PaleoCon Poet in Residence.

This happened to be the 20th anniversary of the museum's opening, and also coincided with the opening of an art exhibit titled "Inspired Collections" - with Max the mastodon as the featured specimen from the collection. I worked on my own watercolor submission and completed it just in time. I was also invited to be the featured artist for this year's PaleoCon - and so I put together a half hour talk covering my own artistic background, summarizing my work - but not chronologically, but by subject. I finished the talk with some words of encouragement and noting that there's nothing special about the art I do, rather that I enjoy doing it, and learning from failed experiments and practicing. I don't consider talent to be a real thing - it's simply developing a skill. I finished on a note explaining that there's nothing keeping anyone in the audience from becoming similarly skilled - and that nobody needs AI to do it for them (which received a surprisingly enthusiastic applause).

Many thanks to Alton for inviting Sarah and I to participate - and major kudos to Brett Dooley for organizing the event! Also, thanks to WSC staff for hosting us. We had a blast and hope to return.

The cast skeleton mount of "Max", the holotype skeleton of the Pacific mastodon, Mammut pacificus, on display in the main gallery at the Western Science Center.

A sampling of Pacific mastodon (Mammut pacificus) mandibles, many of which are from WSC collections. From Dooley et al. (2019).

Visiting paleontologist Melissa Pardi (Illinois State Museum) and WSC director Alton Dooley having a discussion amongst a field of recently acquired plaster jackets.

WSC director Alton Dooley (right) discusses a subadult Pacific mastodon mandible with Melissa Pardi (left), WSC collections manager Brittney Stoneburg (second from left), and WSC preparator Leya Collins (center right).

Visting paleontologists Meaghan Weatherell (left; University of Arizona) and Melissa Macias (right; Duke CRM) working at their laptops. Melissa has been working on cleaning up field notes and GPS coordinates from the initial Diamond Valley excavations to import them into a GIS based map.

Sarah Boessenecker (right) and Melissa Pardi (center) chatting with horse expert and mitigation paleontologist at Cogstone, Eric Scott (left).

The oversize racks at WSC. These are basically all elephants, whales, and jackets containing partial skeletons (e.g. bison, camel, ground sloth).

Several casts of the skull and jaws of "Max", the Pacific mastodon (Mammut pacificus) holotype, are placed on the oversize racks adjacent to heavier actual fossils.

Another Pacific mastodon (Mammut pacificus) specimen consisting of the palate and tusks, in the oversize collection.

Paleontologist Win McLaughlin (Southwestern Oregon Community College) pieces together some kind of fossil pig from one of her field sites in Kyrgyzstan.

The lovely original skull of "Max", the Pacific mastodon holotype (Mammut pacificus).

Win McLaughlin (left) shows Brian Beatty (New York Institute of Technology) a small giraffe specimen from one of her field sites in Kyrgyzstan. (Brian is a longtime friend of the blog and coauthored our papers on Coronodon and Ankylorhiza).

A closeup of Win McLaughlin's early giraffe mandible from Kyrgyztan.

Win McLaughlin and Alton Dooley discussing some small ungulate teeth.

Visiting paleontologist Ascanio Rincon studying a whole glut of fossil ground sloths - Ascanio is a paleontologist from Cogstone.

Meaghan Weatherell (University of Arizona) looking through a drawer of Carboniferous plant fossils from Mazon Creek in Illinois.

Meaghan Wetherell (lower left), Melissa Pardi (lower right on left) and Brittney Stoneburg (both images) perusing Mazon Creek specimens at WSC.

WSC collections manager Brittney Stoneburg and a lovely Pacific mastodon (Mammut pacificus) mandible that needs some more glue in spots. Melissa Pardi explained to me that it has really weird, steeply inclined wear facets on its teeth - which you can see here on the right side (left molars).

WSC preparator Leya Collins giving the same jaw some much needed TLC and applying some consolidant to some of the problem cracks on the specimen.

WSC preparator Leya Collins piecing together some hindlimb bones of a smaller Pleistocene land mammal.

Melissa Pardi (Illinois State Museum) and the same Pacific mastodon (Mammut pacificus) mandible.

Visiting paleontologist Peter Kloess (Riverside City College) shows a young visitor fossil birds from Diamond Valley (from Paleocon 2025).

Peter Kloess brought this 3D print of the lower jaws of the bony toothed bird Pelagornis chilensis. I was surprised at how small it seemed compared to Pelagornis sandersi from Charleston!

The mounted skeleton of "Xena", a Columbian mammoth (Mammuthus columbi), from Diamond Valley.

The exquisitely preserved skull and tusks of "Xena" the Columbian mammoth (Mammuthus columbi).

A giant ground sloth skeleton under glass - I think this one is a Paramylodon.

Sarah and I holding a cast of a Diorocetus whale mandible from the Miocene of Virginia - which Alton produced before he left the Virginia Museum of Natural History. (This was actually from PaleoCon last year in 2025).

A couple of Pacific mastodon teeth (Mammut pacificus) in a jacket.

Melissa Pardi (Illinois State Museum) explaining mastodon tooth anatomy to a visitor. From PaleoCon 2025.

The Friday of PaleoCon I spoke with over a hundred middle school students about paleontological art and scientific illustration - while I did a still life watercolor of this Pacific mastodon (Mammut pacificus) tooth. Here it is after my first couple of coats of paint.

Yours truly working on my watercolor of the mastodon tooth. Photo by Sarah Boessenecker.

A closeup of the watercolor. Photo by Sarah Boessenecker. The watercolor was eventually purchased by my colleague Eric Scott! Thanks Eric!

Yours truly at my table, fielding questions from a bunch of middle school students. I was quite surprised: about 90% of the girls said they liked to draw or paint, and about 2/3 of the boys as well; some even painted with acrylics, one boy and one girl even said they did digital painting/illustration! Not a single student, however, said a word about using AI. The kids are alright.

The opening reception of the "Inspired Collections" art exhibit - many visiting scientists are seen here, including Brian Beatty (far left), Meaghan Weatherell (up front and center), Melissa Macias (in black on right) talking to Ascanio Rincon (blue shirt, gray hat).

WSC director Alton Dooley gives some opening statements at the opening reception for "Inspired Collections".

Here is some of the lovely artwork from the exhibit:

This block print was made by WSC collections manager Brittney Stoneburg!

And yours truly with my watercolor, "Western Leviathan".

This is about 16" wide - large for me. I'm very pleased with how it turned out. The skull of the Pacific mastodon holotype "Max" is shown half submerged, a reference to the Diamond Valley reservoir itself - with the skyline to the east and Mount San Jacinto in the background. Altogether this one took me about ~20 hours or so to complete.

A nursery for giant sharks in the Charleston Embayment: Carcharocles angustidens in the Oligocene Chandler Bridge Formation

2026-07-31T10:17:41.233-07:00

Summer 2018 was spent visiting this locality after every rainstorm to collect as many fossils in situ from the Oligocene Ashley Formation and Chandler Bridge Formation as we could before the pond filled up and the fossil beds drowned - establishing an important benchmark collection. In the process, we made a number of important discoveries - like the nursery assemblage of teeth belonging to the extinct giant shark Carcharocles angustidens.

Background and Discovery

Back in 2018 a new fossil site opened up in Ladson, South Carolina, just about a half hour drive from our apartment at the time in West Ashley. I got a panicked phone call from a friend and fossil collector, that it was raining, and there were two fossil dolphins weathering out. One had just been carted off a few hours prior, without landowner permission. My friend, however, happened to be the brother in law of a regional manager for the construction company that was building at the site. My friend explained that he had a second fossil dolphin, exposed in really soft rock, and that he was worried about it weathering out in the rain that night. "It's 11 pm" I told him. "I'm not leaving the apartment tonight. I'll meet you out there tomorrow. Cover it with a tarp and it will be fine." I headed out the next day to check out the fossil, and it was indeed some sort of long-snouted dolphin in the Chandler Bridge Formation. It was exposed on the side of a spectacular stormwater retention pond which had been dug to a depth of about 30 feet. I was perhaps less interested in the dolphin than I was at the prospect of sampling in situ fossils at this locality. Later on, the subdivison was called McKewn Homes - referred to in our study as the McKewn subdivision or McKewn site. (A frustrating part of Charleston paleontology is that these construction sites never have names until homes start being put up, typically long after you've already started collecting; you always have to call it something - and then that name invariably gets changed later on).

My first foray at the McKewn site - we stuck it out as long as we could before storms rolled in. A storm always seemed to be just off to the horizon.

Stratigraphy of the McKewn site - from Miller et al. (2021).

Individual formations exposed within the enormous pond at the McKewn site, with Ashby Gale for scale on the right side. Two members of the Ashley, the Chandler Bridge and an unusual upper sandy unit, and the overlying Ten Mile Hill Formation were all exposed. Photo by the author.

You see, the Ashley Formation and the Chandler Bridge Formation - despite producing what is perhaps the world's largest assemblage of marine vertebrates, and certainly marine mammals and sea turtles of Oligocene age (34-23 Ma) from anywhere on earth - are quite poorly exposed. Most of the exposures are temporary: either they are construction sites, or stream or river exposures that erode away or might be covered by slumps or vegetation. The South Carolina lowcountry is quite flat, and there is very, very little natural topography - it's also subtropical, so plants grow very quickly there. When I looked around this excavation for the stormwater retention pond, I saw fossils everywhere, and five clear layers: the Runnymede Marl and Givhan's Ferry members of the Ashley Formation, the typical Chandler Bridge Formation, an unidentified clean 'beach sand' unit where the dolphins had come out of, and the Pleistocene deposit on top (later determined to be the early late Pleistocene Ten Mile Hill Formation). I envisioned being able to sample directly from each layer, without any guesswork. Frequently, local collectors without any grasp of stratigraphy would tell me, confidently, that their 'megalodon' or mastodon tooth had come from the Chandler Bridge Formation. "What makes you say that?" I'd ask - and usually the only reply would be a couple of blinks and a surprised face. Folks don't really press each other for details or demand proof of things down there. I'd have to explain that not all shark teeth in Charleston came from the Chandler Bridge; some were from the Ashley Formation, and many others were from overlying Pleistocene units. It could be tough to tell the Chandler Bridge from the overlying muds and sands, but generally, if it was a fossil that was clearly Miocene or Pliocene (e.g., a megalodon tooth) or Pleistocene (e.g., a mastodon or mammoth tooth) - it was assuredly not from the Chandler Bridge, which is much older. In some cases, We'd receive donations and the stratigraphic unit marked would be a big fat '?'. In others, based on some adhering sediment and a geologic map (or occasionally a photo of the fossil in the ground), I'd be able to do some homework and figure out a likely layer that it was derived from. But, there was always a degree of uncertainty. Most of the fossils in our little museum had some degree of stratigraphic uncertainty. This was my first opportunity to collect specimens locally that required no guesswork.

Ashby Gale looking for bones in the upper Chandler Bridge Formation at the McKewn site in May 2018.

Fortunately, spring semester at the college had just ended, and I had all summer to do fieldwork at this new locality. Unfortunately, summer was just beginning. My initial foray at the McKewn site with Ashby Gale was on an overcast day in May where it was only about 80 degrees or so; I still roasted. Fieldwork began a few weeks later, and by early June, the thermometer was already hitting triple digits. Every time I went out, rain water and groundwater seeped into the pit and began filling it up. With this in mind, I began targeting the layers lower down first - I spent quite a bit of time quarrying into a bonebed at the boundary between the two members of the Ashley Formation, collecting both macrofossils, and saving microfossil-rich matrix. I would stuff about 10 lbs of micro matrix into walmart shopping bags, and put one bag on the front and back of my jacob's staff (a wooden pole marked off in 10 cm black and white bands) and carry it out with the pole over my shoulder.

Carcharocles angustidens teeth found during quarrying of the Ashley Formation, before it was indundated with pond water. Photos by the author.

In addition to the quarrying efforts in the Ashley Formation, I carted off about 200 lbs of Ashley bonebed matrix for screening. The very same thunderstorms exposing new fossils a few times a week were leveraged at home - I put the matrix into my box screen which I left under the edge of the roof where a ton of water came off. I remember hearing thunder late at night and leaving the living room (or even the dining room table) to dump another bag of matrix into the screen before it began dumping! Inset shows a small scallop (?Aequipecten) and a snaggletooth shark tooth (Hemipristis serra). Photos by the author.

On one afternoon, I spent about four hours quarrying into this bonebed - alone, since Sarah was in the UK for a couple weeks for graduate school, in 104 degree heat (and something like 80-90% humidity). I made about 7 or 8 trips with the walmart bags, and on my second to last trudge through the hot mud, my camelback hose ran dry. I had already filled it with the rest of my emergency water kept in the car an hour or so earlier - and I hadn't peed once. I still had two bags full of matrix and my field gear at my little quarry. Worse, my honda didn't have AC. I made the trek back, dropped everything off in the car, and drove a couple of miles to a Spinx gas station in Ladson and bought a gatorade and just stood below the AC vent in the convenience store. I bought another gatorade for the drive home. And, because tap water gets no colder than about 75 degrees or so in the South Carolina summer, I poured a "cold" tub and dumped every ice cube in the fridge into the tub.

The second pond at the McKewn site the day I began finding loads of Carcharocles angustidens teeth. Photo by the author.

The collection of Carcharocles angustidens teeth made in just a couple of visits to the new pond. Photo by the author.

A the night before Sarah returned, I went out to the construction site at 5pm (we had permission to collect, so long as we started after daily construction work was done). There was a second pond that I hadn't really prospected much, and so I wanted to check it out. It was small - maybe 1/4 the size of the main pond, and filled up a little more - the water level was just about a foot below the Ashley-Chandler Bridge contact. I walked around on the Ashley limestone to look for fossils in the basal phosphatic bonebed of the Chandler Bridge. I spotted the distinctive reddish root and pale greenish gray enamel of a large tooth - a juvenile tooth of a Carcharocles angustidens, the ancestor of Carcharocles megalodon. These teeth are large and beefy, but still have comparatively dainty crowns and most are more curved than the broadly triangular crowns of C. megalodon teeth. Further, they retain the lateral cusplets seen in older species of the same lineage, including Otodus obliquus (the last non-serrated species in this lineage, from the Paleocene and earliest Eocene), and the middle-late Eocene Carcharocles auriculatus, commonly known in the Eocene rocks of Harleyville closer to I-95.

The entire sample of 32 juvenile (and neonate) Carcharocles angustidens teeth that Sarah and I made from the McKewn locality, and served as the basis for later study.

A few minutes later, I spotted another root. I gently wiggled it - and it also had a complete crown. I pulled a few more teeth. After about 15 minutes, I had found nearly ten teeth. I couldn't wait to show Sarah this locality once she returned. I immediately began thinking about this. All of these teeth were from juveniles - most between 1-3" in length (~3-7 cm). A colleague of mine, Bob Purdy, had published some observations in a 1996 book chapter including that the Chandler Bridge Formation was likely to be a megatoothed shark nursery, and that of a sample of about 100 specimens, only a few were from large adult teeth and most were juveniles. Purdy had mentioned this in a couple of paragraphs and shown a photo comparing a small and large tooth, but nothing had been published aside from this. These specimens had been collected as part of a controlled excavation in the Chandler Bridge Formation, also in Ladson, but about a mile away from the McKewn site - and long since built over by some apartments; my colleague Jonathan Geisler showed me the apartments a few summers later when he stayed with us for a couple weeks of research. Sarah flew back in, and I excitedly told her about the teeth from the new locality - and we went out the night after she flew back. She and I found another half dozen or so teeth in the span of 30 minutes.

Two of the Carcharocles angustidens teeth that Bob Purdy figured from the original sample of 95 specimens from the Chandler Bridge excavation, a few miles away, in his 1996 book chapter. The big one is ChM PV 540 and you can see it below in our figure.

Sarah giving into the mud during the search for fossils in the Chandler Bridge Formation. She has a habit of getting a lot filthier than me when we go do fieldwork - and this was exaggerated in the muddy lowcountry! Photo by the author.

Sarah Boessenecker showing off one of the larger juvenile Carcharocles angustidens teeth - and some of the other teeth we found at that pond that night, and two evenings prior. Photos by the author.

We first met Addie Miller around 2018 as a museum docent and she began working as a teaching assistant for my labs shortly thereafter - one of my favorite TAs! Addie worked extensively with us in the museum and was one of our very favorite students. She also spent considerable time helping Sarah and I clean, repair, and paint the Dorudon atrox (archaeocete whale) skeleton, "Manaia" - given to us by my California colleague Doug Long, who had himself rescued it from the Discovery Channel store in San Francisco and kept it in his Tiki Bar after several northern California museums passed on it. Sarah, Addie, and I spent hundreds of volunteer hours fixing this thing up and getting it ready for exhibit without any assistance.

Over the rest of the summer, Sarah and I continued to return to the site, and by the time that the pond had filled up completely around Labor Day, we had collected 32 teeth of Carcharocles angustidens. I was, at the time, focusing on working on papers on the gigantic dolphin Ankylorhiza (published in 2020) and a monograph on the archaic dolphin Xenorophus (published in 2023) and figured I would get to it later, or assign it to a particularly enterprising student. A few months later, I had my student: Addie Miller was in my 'Applied Paleontology' course that fall, a special topics course all about learning methods in paleontology. She really shined quite brightly, and I encouraged her to undertake an independent study with me at some point. A few semesters later, she and I had a chat, and we agreed to have her work up our assemblage of Carcharocles angustidens teeth for a Spring 2020 independent study. After a few weeks of discussing our modest assemblage of about 30 teeth, I wondered if the specimens that Bob Purdy had mentioned in 1996 were located in Charleston Museum collections: many specimens that had been in Al Sanders' office had been separated from their documentation after his retirement. I contacted Matt Gibson, and inquired about the specimens. He told me that there was indeed a large sample of 95 teeth (I suspect Purdy - or, very likely Al Sanders - rounded the number up to 100) from one locality in the Chandler Bridge, identified as Bed 3 of the Chandler Bridge - ours was mostly from Bed 1 and 2. He spent some time tracking down specimens and doing some cataloguing work for us.

The sample of Carcharocles angustidens teeth from the Chandler Bridge excavation in 1970-1972, also in Ladson, a few miles away. From Miller et al. (2021).

Addie Miller taking notes and measurements of Carcharocles angustidens teeth at Charleston Museum. Photo by the author.

We visited Charleston Museum on February 19 and Addie measured all of the teeth, and took cell phone photos for preliminary identification of their position in the jaw. We had planned on bringing a bigger DSLR camera and getting publication quality images later on; Addie had already taken all the photos needed for the specimens from our locality. We're lucky that we visited when we did - only day after our friend Jane Kelly had returned from the American Association for the Advancement of Science meeting (AAAS) and told us that the country was probably unprepared for the novel coronavirus that was beginning to spread beyond China. Ten days later the first US death from Covid-19 occurred, and within three weeks, the USA - and even South Carolina, for a brief time - were on lockdown. Later that fall, Matt Gibson obliged us in taking the required photographs since we wouldn't be allowed back into Charleston Museum for another 16 months or so in mid 2021.

A selection of large Carcharocles angustidens teeth, largely found ex situ and lacking associated stratigraphic data, in the collections at Charleston Museum. Photo by the author.

Shark Nurseries and sampling bias in the Lowcountry

Shark nurseries or nursery areas have generally been proposed to be shallow, warm, semiprotected embayments where certain species of sharks may visit and give birth in, with the pups and juveniles sticking around for some time while they grow - eventually growing large enough to leave. These areas are generally thought to be relatively scarce in oceanic predators, including other sharks of the same species. Bulls Bay, South Carolina, is one such example, being host to a number of species including sandbar, blacktip, dusky, smooth dogfish, hammerhead, and several other species.

The major problem with studying fossil sharks and establishing whether or not the assemblage reflects a nursery has nothing to with establishing whether or not the environment was appropriate. The Charleston Embayment was shallow, certainly tropical to subtropical thanks to certain fossil fish and pollen, and based on microfossils, was likely shallow marine and protected, even trending to brackish/estuarine settings by the top of the unit (Bed 3). The major problem is that of collections bias. Shark teeth are popular finds for collectors of all ages - and what do collectors like? Trophies. Carcharocles angustidens teeth are some of the most desired of all trophy species from Charleston, right up there with C. megalodon and the extinct 'false mako' Parotodus benedeni, a close relative (these teeth are perhaps the most prized by the diggers and divers who have been doing it the longest; I judged collectors experience based on how many Parotodus teeth they had found - and judged their skill based on how many cetacean skulls they had properly excavated). But I digress. If a paleontologist has access to a site shared with amateurs, the scientist is more likely to have an unbiased sample. However, the amateurs might get to the site earlier in the day, more frequently, or visit at night with headlamps, and find larger teeth, leaving smaller teeth behind - thereby biasing the sample.

Ashby Gale prospecting the mysterious upper Chandler Bridge Formation at the McKewn site. Photo by the author.

In the case of our locality in the McKewn subdivision, the construction firm that owned the land and was developing it had been pretty blunt with fossil collectors and word got out fast that they didn't want anyone other than a handful of folks with strict permission to be out there. The folks who carted off an Oligocene shark-toothed dolphin skull without permission did not return, and I was instructed by the regional manager of the company to warn anyone I suspected of fossil poaching to get off the property. A small price for access, I suppose; the company got some good PR with the local college and museum, and got a free security guard in return. Generally speaking, I saw a couple of folks who said they were looking for arrowheads (I myself had found a couple), and saw some poachers looking in all the wrong spots - I suppose for megalodon teeth. Nobody, not even my friend who had found the dolphin, was looking in the pond excavations. By July Sarah and I had moved into our house in North Charleston, a four minute drive away, and we were always the first onsite right after a rain - and, truth be told, we didn't really see anyone else out there, and in between afternoon thunderstorms, there weren't any new fossils eroding out. All told, we were reasonably certain we had an unbiased sample. The Chandler Bridge excavation site, quarried in 1970-1972, was even more of a slam dunk because all teeth had been kept by the Charleston Museum crew and there simply wasn't any private collecting permitted. Every vertebrate fossil from the 21x21 meter gridded excavation pit was kept by the museum.

A vertebra of Carcharocles megalodon showing growth rings, and under X-ray, annual growth bands - indicating that this shark was nearly 50 years old when it died. From Shimada et al. (2021).

How do you tell a shark's age?

Determining the age of live animals is difficult, unless they're pets, in a zoo, or tagged while young juveniles. For dead animals, it's a bit more difficult. Tooth wear can often be used in modern mammals, especially herbivorous ungulates. Growth bands in teeth (growth layer groups) are often useful as the deposition of dentin slows in the winter, leaving annual banding that is visible under a microscope. For sharks, it's quite a bit more difficult. Vertebrae have similar growth rings, and if sectioned properly (they are calcified cartilage, not bone) growth bands can be counted. Changes in DNA relating to growth can be sampled and analyzed, called DNA methylization. Shark tissues can also be radiocarbon dated - a greenland shark (Somniosus microcephalus) had lens nuclei dating to over 272 years in age, and surprisingly, many specimens around two meters in length had lens nuclei showing the 'radiocarbon bomb spike' from the 1950s-1960s spate of nuclear tests.

While counting growth rings offers a degree of precision, it is less useful for fossil assemblages like ours since it is always tricky to identify shark vertebrae to the species level - and in our case, we had a ton of teeth, rather than vertebrae. Teeth are formed, temporarily brandished in the mouth, and then shed - practically the opposite of an archive of growth, unlike the vertebrae. They are, instead, more akin to a 'snapshot' - roughly how large the shark was at the time the tooth was shed. Tooth size is much more rough, but with teeth, you get a much larger sample. Was this really a nursery assemblage? We would need a few data points first.

The dentition of Carcharodon carcharias and the relationship between tooth position and body size, with several linear regressions for different teeth on the graph below. From Shimada (2002).

Fortunately, our colleague Kenshu Shimada had published a few papers about two decades prior where he took measurements of teeth from sharks of known body length and plotted tooth size v. body length, generally resulting in a linear relationship. Sharks grow slow and apparently close to isometrically - their growth rate is constant. Us mammals grow rapidly when we're juveniles and slow down after puberty. Birds grow even more absurdly rapidly, condensing most of their growth into their first year of life. Precisely how slow ancient 'reptiles' and dinosaurs grew has been a huge debate during the course of my entire career, and what sort of curve best fits that of dinosaurs - and if some mathematical assumptions of one curve over the other has completely messed up some estimates of dinosaur aging.

The dentition of Carcharodon carcharias (top) and reconstructed dentition of Carcharocles megalodon (bottom) from an associated tooth set. From Perez et al. (2021).

The reconstructed dentition of Carcharocles angustidens, based on the only known complete dentition - OU 22261, from the Otekaike Limestone of New Zealand. Ewan Fordyce showed me the locality when I was a Ph.D. student and I walked past one of the blocks of teeth every day to my office. Addie based her identifications to tooth position on this diagram, with one modification: we omitted the "intermediate tooth" with an upper third anterior position, like the lower dentition. The intermediate tooth is present in the modern great white shark, Carcharodon carcharias, which we do not think is closely related - but was invoked in several studies from the 90s and early 2000s to highlight a close affinity with Carcharodon, rather than Carcharocles. From Gottfried and Fordyce (2001).

Addie's first task was to identify each tooth to position - and then enter her measurements into the linear regression equations that Shimada had demonstrated for the modern great white shark. We don't think that they are particularly closely related, but given the broad similarity of the teeth, it's probably good enough. This was necessary because the teeth are different sizes: the largest teeth are from the front of the mouth, and they decrease in size further posteriorly. As a result, if we were just to plot tooth size - we would be underestimating the size of the sharks that had shed the lateral teeth. The only established method results in a body length estimate, so we figured we could plot all of the body length estimates for all 32 teeth - and the 95 teeth from the Purdy sample. This would give us a population curve of sorts, and tell us what body lengths were the most common - and the most rare. We followed a paper by Pimiento et al. (2010) on a Carcharocles megalodon nursery from Panama.

The sample of the largest teeth of Carcharocles angustidens, which Addie used to estimate the maximum body length - and, therefore, the cutoffs between neonates, juveniles, and adults. From Miller et al. (2021).

Next up, we needed to know what the maximum size of the species Carcharocles angustidens was. This is actually a pretty difficult problem - since we would need to measure the largest known teeth of this species. Large teeth of C. angustidens are trophy specimens. Fossil collectors in the lowcountry might hand over fragmentary cetacean skeletons after much negotiating and encouragement, but they rarely ever cough up prized shark teeth. The shark teeth are the whole ball game down there: us whaleontologists got fossil cetaceans donated because they were discovered during the search for shark teeth. Shark teeth are big business in the southeast. Fortunately, there was one large tooth in the college collection which we were able to figure and measure, and a handful of similar to slightly larger specimens in Charleston Museum collections. Once we had our maximum size of C. angustidens from these specimens, we subdivided the size estimates into three categories: neonates, juveniles, and adults. We took the maximum length estimates of C. megalodon from the earlier Pimiento study and 'shrunk' them to fit the smaller maximum body length of C. angustidens - this resulted in the neonate-juvenile cutoff at 2.6 meters, and the juvenile-adult cutoff at 6.8 meters. The single largest tooth, Charleston Museum specimen 7267, was estimated to be a whopping 11.25 meters (37 feet). While I have not seen them personally, I am certain that larger specimens probably exist in private collections - and I had no interest in trying to beg and plead for such specimens to be donated for our study. What collector is going to donate a specimen after I tell them they have the world's largest?

This is not the largest tooth I've ever found, nor is it the largest Carcharocles angustidens specimen out there - but ironically, it is a trophy specimen of mine which even I never donated - for a number of reasons. I've also intentionally left the barnacles and bryozoans on it, lest it become just another tooth. I found this in July 2020 with Ashby Gale and Sarah. Photo by the author.

As it happens, we got this right under the wire: there have been a slate of papers that came out in the next couple of years and have reignited the debate over the maximum body size of megatoothed sharks, specifically C. megalodon. Reignited is perhaps too soft a word: exploded may be more appropriate, in more ways than one. It now seems as though the Carcharodon carcharias based estimate of about 15-16 meters (~45-50 feet) based on tooth size from the 1990s is far too conservative, and new papers using the maximum dimensions of the jaws based on associated tooth sets indicating sizes up to 20 meters (Perez et al. 2021) and even 24 meters based on rediscovered gigantic vertebrae from Denmark (Shimada et al. 2026). It's likely that these methods, if applied to C. angustidens, may result in some changes in the maximum length, but are unlikely to change the cutoffs used in our study, and in any event, will not change the juvenile-dominated pattern.

Histograms of reconstructed Carcharocles angustidens body lengths from the McKewn subdivision sample (top) and the Chandler Bridge excavation (middle), and the two combined together (bottom). As you can see, the sample realy is dominated by juveniles. From Miller et al. (2021).

Scientific Results from the hot mud of the Lowcountry: a nursery sample after all?

When Addie entered all of the data in and generated a graph (histogram) of the sizes, I was actually a bit surprised. I knew that juveniles were common, but I did not really expect them to be essentially the only specimens in our sample from the McKewn subdivision. There was one neonatal tooth, 31 juveniles, and zero adults. I was further blown away by the Chandler Bridge excavation sample from bed 3 - out of 95 teeth, there were three neonates, six adults, and the remaining 86 were from juveniles. Addie combined the two datasets together, and the result was a rather pleasing near-normal distribution of body sizes, with a peak around four meters body length - 31 specimens, about 1/4 of the entire sample. Most of the adults were on the right-hand tail of the curve, and two enormous teeth were outliers at around 10-11 meters - with zero teeth representing body sizes from 7.5 to 10 meters. This strongly suggests that most of the adults are the tail end of the resident juvenile population, with a few true adult giants visiting rarely. Altogether, this supports Purdy's original proposal that the Charleston Embayment was in fact a nursery for megatoothed sharks - and the only established nursery for the Oligocene epoch.

A nursery assemblage of Carcharocles megalodon teeth from the upper Miocene Gatun Formation of Panama. From Pimiento et al. (2010).

A survey of Carcharocles megalodon teeth from nine different localities around the world. The eastern Iberian peninsula (red), Calvert Formation of Maryland (light orange), Gatun Formation of Panama (pale yellow), the Chucunaque Formation of Chile (yellow-green), and the Bone Valley Formation of Florida (blue) all have relatively smaller teeth and have been proposed as nurseries. From Herraiz et al. (2020).

Nurseries have also been proposed for C. megalodon in Panama, the western Mediterranean, Salisbury Embayment (Calvert Formation), Florida (Bone Valley Formation), and the Chucunaque Formation of Chile. There has been a bit of back-and-forth over these, with certain researchers squabbling over small sample sizes and what statistical approaches were appropriate or not.

The pond at the McKewn subdivision filled up rapidly - the top image is from July 2018, just two months after we began fieldwork there. The pond was full by Labor Day. The bottom is from July 2019, after several homes had been built, and the banks had become completely vegetated. I couldn't replicate the same angle as the first photo because the earlier photo was taken about 10 feet further down and 30 feet closer. Photos by the author.

What's really remarkable is that this shark assemblage essentially demonstrated the process of repeatability in paleontology. You can argue until the cows come home about fossils sitting in museum collections, but sometimes, the only way to test a historical hypothesis is to go out and dig up a bunch more fossils. In this case, Bob Purdy had made a hypothesis based on a sample of teeth from an excavation conducted in the early 1970s - and we had essentially tested the hypothesis using a completely different sample of teeth from the same rock unit a few miles away, and under somewhat different conditions. We failed to reject Bob's hypothesis, instead reinforcing it. Given that Bob had never published the original specimens, we decided to include that and produce a much more robust study.

The large pond at the McKewn development in May 2018 (top), July 2018 (middle), and July 2019 (bottom). The last photo is not taken at the exact same location. Photos by the author.

The Chandler Bridge excavation pit is now partially built over, and the pond at the McKewn Subdivision is completely flooded. Neither locality is now accessible - the former being much more permanent, given that some ponds can be pumped out and drained - after all, we dug at the Austin Sand Pit in 2022, four years after the owners flooded it. Now it's a motorboat test pond and won't get drained again until there's new management. At McKewn, the pond is encircled by duplexes and townhomes, and probably won't ever be drained. We'll have to wait for another construction project - but there's not many fossiliferous areas left in the Charleston area to dig down into.

A Taxonomic Note

I probably ought to write an entire blog post about this - but we decided to stick with the genus Carcharocles instead of Otodus. We have a taxonomic discussion and outline the fact that use of Otodus relies upon a bunch of untested phylogenetic assumptions. These assumptions may turn out to be true - but in the ten years since this taxonomic proposal has been made, dozens of papers have accepted it blindly and zero have tried to test any of the underpinning phylogenetic assumptions. We viewed - and I still view, five years later - the move to place the species of serrated megatoothed sharks in Otodus as premature. I briefly followed along in 2019, but not a single followup study attempted to make a strong case for it, so I decided to appropriately backtrack. Another strenuous argument in favor of continuing to use Carcharocles was made by Kent (2018). I could be wrong! I'm not afraid to be wrong - but someone needs to prove it first.

The sample of Carcharocles angustidens teeth from the Ashley Formation, found at the McKewn site in 2018. From Miller et al. 2021.

First records of Carcharocles angustidens from the Ashley Formation

In addition to the sample from the Chandler Bridge Formation, we also reported about nine teeth of Carcharocles angustidens from the Ashley Formation at the McKewn subdivision. Surprisingly, none had ever been found in situ before, anywhere - loads and loads of isolated teeth have been reported from riverbanks, riverbottoms, and beaches over the past 150 years. However, these were all found ex situ - possibly eroded our of the Ashley Formation, Chandler Bridge Formation, or - heaven forbid - the poorly known Edisto Formation. Unsurprisingly, virtually all of the teeth from the Ashley Formation were also from juveniles or possibly large neonates. Altogether, this suggests that the Charleston Embayment served as a megatoothed shark nursery for several million years.

Addie Miller and I at her graduation, holding two of the teeth from her study in front of the shark exhibit at our museum (sadly, it was taken down). I am immensely proud of Addie's publication and her work! Photo by Sarah Boessenecker.

Thanks to Sarah Boessenecker and Ashby Gale for extensive field assistance, Matt Gibson for contributing data and photographs from Charleston Museum, Jonathan Geisler for extensive discussions on Charleston paleontology, the late Al Sanders and his army of students who excavated the Chandler Bridge site, and of course, major thanks to Addie Miller for writing a kickass scientific study.

You can read our open access paper in Palaeontologia Electronica online here for free.

Further Reading

Cicimurri, D.J. and Knight, J.L. 2009. Late Oligocene sharks and rays from the Chandler Bridge
Formation, Dorchester County, South Carolina, USA. Acta Palaeontologica Polonica, 54:627-
647. https://doi.org/10.4202/app.2008.0077

Cooper, J.A., Pimiento, C., Ferrón, H.G., and Benton, M.J. 2020. Body dimensions of the extinct
giant shark Otodus megalodon: a 2D reconstruction. Scientific Reports, 10:14596.
https://doi.org/10.1038/s41598-020-71387-y

Gottfried, M.D., Compagno, L.J.V., and Bowman, S.C. 1996. Size and skeletal anatomy of the
giant “megatooth” shark Carcharodon megalodon, p. 55-66. In Klimley, A.P. and Ainley, D.G.
(eds.), Great White Sharks: the Biology of Carcharodon carcharias. Academic Press, San
Diego.

Gottfried, M.D. and Fordyce, R.E. 2001. An associated specimen of Carcharodon angustidens (Chondrichthyes, Lamnidae) from the Late Oligocene of New Zealand, with comments on Carcharodon interrelationships. Journal of Vertebrate Paleontology, 21:730-739.
https://doi.org/10.1671/0272-4634(2001)021[0730:AASOCA]2.0.CO;2

Herraiz, J.L., Ribé, J., Botella, H., Martínez-Pérez, C., and Ferrón, H.G. 2020. Use of nursery
areas by the extinct megatooth shark Otodus megalodon (Chondrichthyes: Lamniformes).
Biology Letters, 16:20200746. https://doi.org/10.1098/rsbl.2020.0746

Kent, B.W. 2018. The cartilaginous fishes (chimaeras, sharks, and rays) of Calvert Cliffs,
Maryland, USA. Smithsonian Contributions to Paleobiology, 100:45-157.

Miller, A.E., Gibson, M.L., and Boessenecker, R.W. 2021. A megatoothed shark (Carcharocles angustidens) nursery in the Oligocene Charleston Embayment, South Carolina, USA. Paleontologia Electronica, 24:a19.

Perez, V.J., Leder, R.M., and Badaut, T. 2021. Body length estimation of Neogene macrophagous lamniform sharks (Carcharodon and Otodus) derived from associated fossil dentitions. Palaeontologia Electronica, 24:a09. https://doi.org/10.26879/1140.

Pimiento, C., Ehret, D.J., MacFadden, B.J., and Hubbell, G. 2010. Ancient nursery area for the extinct giant shark Megalodon from the Miocene of Panama. PLoS ONE, 5:e10552. https://doi.org/10.1371/journal.pone.0010552

Purdy, R.W. 1996. Paleoecology of fossil white sharks, p. 67-78. In Klimley, A.P. and Ainley, D.G.
(eds.), Great White Sharks: The Biology of Carcharodon carcharias. Academic Press, San Diego.

Purdy, R.W., Schneider, V.P., Applegate, S.P., McLellan, J.H., Meyer, R.L., and Slaughter, B.H.
2001. The Neogene sharks, rays, and bony fishes from the Lee Creek Mine, Aurora, North
Carolina. Smithsonian Contributions to Paleobiology, 90:71-202.

Sanders, A.E. 1980. Excavation of Oligocene marine fossil beds near Charleston, South
Carolina. National Geographic Research Reports, 12:601-621.

Shimada, K. 2002. The relationship between the tooth size and total body length in the white
shark, Carcharodon carcharias (Lamniformes: Lamnidae). Journal of Fossil Research,
35:28-33.

Villafaña, J.A., Hernandez, S., Alvarado, A., Shimada, K., Pimiento, C., Rivadeneira, M.M., and
Kriwet, J. 2020. First evidence of a palaeo-nursery area of the great white shark. Scientific
Reports, 10:8502. https://doi.org/10.1038/s41598-020-65101-1

The Oligocene dolphin Xenorophus, part 3: new insights into the growth, variation, functional anatomy, asymmetry, and phylogeny of early odontocetes

2026-06-26T09:40:03.577-07:00

This is intended to be the third and final installment in this series, and I'll probably forget something in here - but here goes! The Xenorophus monograph was a monumental task to write and publish, and this "cliff notes" version will probably fail to cover everything. There's a LOT of meat in there, so who knows how many additional posts I'll have to make. To see part 1, click here, and for part 2, click here.

Typological thinking in Paleocetology and Ontogeny (growth) series in an early odontocete

Mammalian paleontologists have never had to worry much about the effects of growth-related changes in skeletal anatomy, because 1) mammals only get two sets of teeth, 2) their skulls do not seem to radically change in ways different than what we observe in modern mammals - as a result, mammalian paleontologists are not faced with the same problems our colleagues in dinosaur paleontology - pretending ontogeny doesn't exist and naming every different growth stage as a different species and then arguing forever about which species are distinct. Jack Horner and Kevin Padian called this "typological thinking" during my time at Montana State - overemphasis on pigeon-holing fossils into cookie-cutter "types". This sort of thinking led to naming different growth stages of tyrannosaurs (Tyrannosaurus rex, Nanotyrannus*), ceratopsians (Triceratops, Torosaurus - still controversial, unfortunately IMO), and even three different species named from 'ontogimorphs' in Pachycephalosaurus (Dracorex, Stygimoloch). This sort of thinking acts as a mental 'blinder' that keeps paleontologists from thinking creatively and flexibly about species concepts and definitions, and prevents consideration of hypotheses that might conflict with their chosen taxonomic framework.

*This one seems to have been settled recently and it seems as though they aren't different growth stages after all.

In marine mammal paleontology, we have different problems that, in my opinion, stem from similar psychological underpinnings, as well as anatomical shortcomings of the taxa we study. To start, certain researchers in the past have overemphasized splitting and holotype-based study. One unnamed scientist told me years ago "stick to holotypes". The un-spoken background here was that some competing researchers had carefully worked with larger samples of the 'species' this scientist had named and declared a bunch of them as synonyms, with new specimens filling in intermediate anatomical conditions. It turned out that the species named by the original researcher all happened to be outliers - and the new specimens instead showed a gradient. If you ignore the middle - the 'referred specimens' - you get to 'keep' all of the species, but only if you ignore data. You can quibble over whether some specimens are correctly identified, but generally speaking, it should always be a red flag whenever a senior scientist tells you to ignore a bunch of data.

Hand-drawn phylogeny of cetaceans, highlighting the diversity of cetacean family-level groups - and perhaps the overemphasis of family level taxa in prior paleocetological thinking. Many of these families are paraphyletic or polyphyletic. Modified from Barnes et al. (1985).

The second psychological problem is overemphasis of family-level groups in cetacean paleontology. I won't point any fingers, but those 'in the know' are probably very familiar with the few key figures. Some of the extinct families in Cetacea are not very well diagnosed in the first place, and frequently some are paraphyletic or even polyphyletic. My coauthor Jonathan Geisler is so averse to this sort of taxonomic thinking he prefers to just follow the phylogenetic tree - the direct signal from the data. We have so many unnamed taxa, especially in the Oligocene, that it is understandable to want to assign every specimen to a particular family - I do it, frequently - occasionally making Jonathan's eye twitch a little bit - but at least in my published writing, try to make it very clear what the definition and diagnosis of each family is. What the hell is a dalpiazinid? I still don't know, and the few fossils considered to be dalpiazinids have since been found to group with Waipatia-like dolphins. I use the term "Waipatiidae" all the time, but I recognize that it very well may be a grade rather than a clade - though some promising analyses by Amber Coste have recently shown it may be a monophyletic group.

The third unique aspect of typology in Paleocetology is the anatomical constraint imposed by the species we study. Most cetaceans simply just do not have particularly diagnostic teeth. Unlike terrestrial mammals, where juvenile and adult skulls can often be easily identified to the same species based on their teeth, dental morphology in cetaceans typically is so variable that species tend to blur together. But, there's more: within Neoceti, there are wildly varying tooth counts, so you cannot make 1:1 comparisons based on the position, with the exception of some toothed mysticetes that have only incipient polydonty - like Coronodon, for example. Oligocene odontocetes tend to have teeth that are readily identified to the family and occasionally genus level, and sometimes have species-level differences that can be distinguished when the teeth are set in skulls - but crown odontocetes from the Miocene and Pliocene have teeth that are frequently not even diagnostic at the family level, with a couple of exceptions here and there. And then there's baleen whales - which, aside from some Oligocene examples, don't even have teeth. All we have to go on is skull and mandibular anatomy, and occasionally vertebral counts for well-preserved skeletons. So, just like dinosaur paleontology, we have 1) teeth that are sort of useless in taxonomy and, in concert with this, 2) large body size associated with some pretty extreme skull shapes that are wildly divergent from the terrestrial mammal 'archetype'. As a result, we frequently have trouble figuring out the identity of juvenile cetacean specimens.

We actually don't have that many fossil cetaceans with growth series. Here's one other growth series that is well-documented - the eomysticetid baleen whale Waharoa ruwhenua, from my Ph.D. research. From Boessenecker and Fordyce (2015).

This is all a long-winded explanation of why I focused on reporting ontogenetic changes in Xenorophus. This is pretty much the first ontogenetic series ever reported for a stem odontocete. Sure, there are a couple of Miocene species out there with a few referred specimens and a juvenile or two (the beaked whale Messapicetus gregarius and Brachydelphis come to mind), but this is the first for any archaic dolphin on the odontocete 'stem' (e.g. diverging earlier than the most basal-branching modern species, the sperm whale, Physeter macrocephalus). Why is this critical? Two key reasons: 1) Because there are a couple of archaeocete whales with growth series, and they do not seem to have quite as much anatomical change during growth that Neoceti have; and 2) we don't really have much of a benchmark for assessing how much growth-related change there is in early odontocetes and what sort of features vary between species versus what varies during growth and can be ignored for the purposes of taxonomy.

Growth of the nasal bones in Xenorophus sloanii. Note that they elongate during growth, and in addition to clearly growing posteriorly, they also grow anteriorly - and appear to make the bony nares face more anteriorly than dorsally. From Boessenecker and Geisler (2023).

I already wrote extensively about the teeth in part 1, so now I'll write a bit about the nasal bones and the 'vertex'. This region is not always well-defined, but generally the area including the nasals and the tip of the occipital shield; this ends up including the sagittal crest in archaic Neoceti and archaeocetes, the frontals, and often the posterior tips of the premaxilla and maxilla. The vertex is typically the most informative area used in fossil cetacean taxonomy - and since it's not tooth enamel that is literally static in shape throughout growth, any changes in the anatomy of the vertex should be put under the microscope. One major evolutionary trend in cetacean evolution is cranial telescoping: the facial bones migrate ever further posteriorly in both mysticetes and odontocetes (and archaeocetes for that matter); a separate pattern, typifying mysticetes and probably a couple of odontocete groups, is anterior migration of the occipital shield. This can result in multiple bones being overridden and excluded from the vertex; the parietals are among the first of these to go (but later on in odontocete evolution - all xenorophids have dorsally exposed parietals). As it turns out, telescoping also changes during growth - with less-telescoped skulls in juveniles and more-telescoped skulls in adults. In Xenorophus, the intertemporal region shortens as the occipital shield increases in length (and becomes laterally broader as well). The nasals elongate, especially posteriorly, but also a little bit anteriorly. Muscle attachment crests all over the facial region become more strongly developed and sharply defined. In old adults, the frontal-nasal suture actually nearly disappears as the two bones fuse together. One curious feature is the rotation of the sagittal crest during growth: it is nearly anteroposteriorly directed in juveniles, but in old adults, it is rotated counterclockwise and points off to the left by about 5-10 degrees - more on asymmetry later.

What does this all suggest? We need to be careful about considering which features may be driven by ontogenetic changes rather than differences in species. For starters, some of these 'psychological blinders' prevented Al Sanders, Jonathan, and I - at least for a time - from considering any specimens as belonging to Xenorophus sloanii. Once the supposedly diagnostic features were realized to be related instead to growth, all the dominoes fell into place. Second - the vertex of a fossil dolphin skull can change quite a bit. Alarmingly, these changes continue far past all of the vertebral epiphyses start to close - CCNHM 104, for example, as a very different looking vertex than CCNHM 1077 and ChM PV 5022, but all of these specimens have a mature/adult stage of vertebral epiphyseal closure. In my opinion, based on this information, we should have at least a handful of solid diagnostic features rather than just one or two - because if you focus on just nasal shape, for example, you might even get three different species out of this collection of Xenorophus specimens.

Functional anatomy of Xenorophus: feeding morphology and oral pathology

Oligocene toothed whales have a surprising degree of feeding adaptations - and this is true even within the Xenorophidae - Inermorostrum has no teeth and a short snout, after all. We know already that there are other small bodied narrow-snouted xenorophids like Echovenator, Albertocetus, and Cotylocara in the Oligocene of South Carolina; there a ton of similarly sized "spear-tooothed" waipatiid grade dolphins, and of course, the giant macrophagous dolphins in the genus Ankylorhiza. How does Xenorophus fit in to this exactly? We'll take a closer look at the teeth, how the teeth interlock, tooth wear, snout shape, and pathologies in these specimens.

The upper dentition of Xenorophus sloanii - CCNHM 168.

The teeth of Xenorophus are absolutely large - some of the largest after Ankylorhiza - but it's also a relatively big dolphin. The skull is quite large, about 60 cm long - and the body is up to about 3 meters, about 3/5 the size of Ankylorhiza tiedemani. Xenorophus is the second largest odontocete in the Oligocene assemblage after the 3-4 species of Ankylorhiza (most are unnamed) - which tells us something at minimum about the trophic level of Xenorophus. But, back to teeth. Xenorophus has incipient polydonty - typically about 13 teeth per quadrant, so two additional teeth from the primitive number for placental mammals (11). The dentition is heterodont, with about six to seven conical caniniform anterior teeth, three to four smooth-edged triangular and bilobate to double-rooted postcanine teeth, and three to four cuspate, wide, triangular, and double-rooted 'molariform' teeth; these are fuzzy boundaries, hence the variation in count. Crown height is similar from the front to the back of the dentition, but the crowns become much 'wider' (in lateral view) towards the back of the dentition. The enamel is smooth on the anterior teeth and develops rugose enamel posteriorly in the molariform teeth. Ridges at the base of the crown, called cingula (singular = cingulum) are present in the posterior teeth on both the inner and outer sides.

The embrasure pits and dental occlusion in an old individual of Xenorophus sloanii, CCNHM 1077.

Xenorophid dolphins are unique amongst odontocetes for retaining deep pits in the mandible and maxilla that accommodate the teeth when the jaws are closed (occluded). This is a primitive feature* amongst cetaceans, inherited from basilosaurid whales - which have comically large teeth, and those teeth need to go somewhere when the animal closes its mouth. The way this works in basilosaurids (and earlier archaeocetes for that matter) is that the anterior caniniform teeth interlock in line with each other, like the teeth of a cartoon bulldog. This is accomplished in two ways: first, the gaps between the teeth are large enough for the opposing tooth to fit, and second, there's a pit - called an embrasure pit - eroded* into the lateral side of the bone in both the upper jaw (maxilla) and lower jaw (mandible). The posterior larger cheek teeth don't have large gaps between them, so the lower teeth actually slide on the 'inner' (tongue) side - aka lingual side - of the upper molars. This means that the anterior teeth typically only have wear facets on the tip of the teeth, wearing from contact with prey during biting, as these teeth don't really touch each other during jaw closing. However, the cheek teeth slide against each other like scissors, so the outer "lip" side of the lower teeth (labial side) gets a shear facet, duplicated on the inner (lingual) side of the upper teeth. These teeth also get worn down at the tips from biting prey. This style of tooth shearing is very similar to the carnassial teeth in mammalian carnivores like dogs and cats.

*The lack of embrasure pits in other odontocete clades makes this a very convenient feature in the formal diagnosis of Xenorophidae and also makes identification of xenorophid rostrum and mandible fragments super easy in the field. At least, here in Charleston, because they basically occur nowhere else.

**I say eroded because when we find archaic cetaceans where such a tooth was lost quickly or did not form, an embrasure pit never forms. In Dorudon atrox, there is a specimen where a tooth was lost evidently early in growth, and on the opposing jaw, there is no embrasure pit. The embrasure pit forms as a bone response to stress imposed by repeated closure of the mouth. Some extant carnivores develop embrasure pits, so I'm sure this could be evaluated in a much larger sample size with modern mammals.

Xenorophus has embrasure pits, but they're a bit different than in basilosaurids. The pits are present in both jaws along the anterior two-thirds of the tooth row, and positioned on the lateral side. This is like the condition in basilosaurid whales - the uppers and lowers are not exactly vertical but splay out slightly. However, there are no embrasure pits on the palate (upper jaw) between the last four upper teeth. Instead, there are deep embrasure pits on the mandible, between the lower teeth, and in line with them. From about the third to fifth lower postcanine tooth, these pits shift from a lateral position to being in-line with the uppers. This means that the upper and lower triangular molariform teeth are in-line with each other, and even more closely resembling a cartoon bulldog mouth! In other words, the mandibular teeth have shifted laterally and they are no longer shearing against each other like archaeocete molars. As a result, the wear on these teeth is chiefly along the front (mesial) and back (distal) cutting edges. However, the tips of these teeth are unworn in most specimens! What's going on there?

Skull of Saghacetus osiris, Stuttgart specimen 11235, from Kellogg (1936). This specimen is one of the only archaeocetes preserved with the upper and lower teeth in occlusion; you can see that the upper molars and premolars lie entirely 'labial' (on the outside) of the lowers, and the anterior teeth (incisors, canine, anterior premolars) lie in line with one another. In Xenorophus, on the other hand, all of the teeth are in line.

What's interesting here is that while this style of occlusion is very different from archaeocete whales - AND modern dolphins. This dentition is functionally adapted for biting prey along the entire length of the jaw, unlike archaeocetes, where only the anterior dentition was likely used for prey capture, and the molars used instead for 'prey processing' (aka chewing). This is basically the way modern dolphin jaws work - despite the embrasure pits. We hypothesized that the embrasure pits deepen so much so that the tips of the teeth never impact enamel from the opposing dentition, maintaining their sharp apex no matter how much of the mesial and distal edges become worn down. In old adults like CCNHM 1077, the embrasure pits are SO deep that the entire crown would have fit into a gum-lined pit and only the roots of the teeth contacted each other - the little wear that did happen to these teeth are a vestige from an earlier stage of growth. What's interesting here is that while the dentition is certainly anatomically heterodont, much of the evidence suggests that it was functionally homodont.

The highly worn teeth of the Bailey specimen of Xenorophus sloanii, CCNHM 168.

Only a single specimen has worn tooth apices - CCNHM 104 - which is an unusual specimen. CCNHM 104 is osteologically a subadult and it is not large - but it has a rather extreme degree of tooth wear, more extreme than any other specimen. There are a few possibilities that explain this. Perhaps it is actually ontogenetically very old, but had stunted growth, and the gaps between the teeth never became large enough to spare the tips from wear. Another possibility is that this individual consumed prey that was more abrasive, such as sharks - the dermal denticles wear down the teeth of modern offshore killer whales quite rapidly, and right down to the gumline. So, maybe it wore down its teeth rapidly and before the gaps could fully accommodate the teeth.

Missing teeth and a gnarly jaw infection in Xenorophus sloanii. From Boessenecker and Geisler (2023).

There are a couple of interesting pathologies in Xenorophus. Specimen ChM PV 7677 is missing four upper teeth, and CCNHM 168 is missing four lower teeth. In ChM PV 7677, there are ghosts of tooth sockets left, where there's a small irregular patch of bone with a few vascular foramina (holes for blood vessels) present. In CCNHM 168, these missing teeth in the mandible are further associated with what seems to be a healed fracture and bony callous in the right mandible and a pretty disgusting looking pathology with a large open window in the left mandible, right at the same position as the missing teeth, just posterior to the mandibular symphysis. Perhaps both mandibles suffered a hairline fracture here, with a pretty nasty infection - perhaps osteomyelitis - developing on the left side. This infection may have led to the loss of the teeth. We proposed that, between this and the possibility that CCNHM 104 fed upon unusually abrasive food (more likely than stunted growth in my opinion) - that Xenorophus may have engaged in risky feeding behavior. At such a large body size, it may have been tempting to go after prey that was larger and more difficult to capture than regular fish. This risky feeding behavior perhaps contributed to an unusual degree of tooth loss, mandibular fracture, and tooth wear.

Lastly, Xenorophus has a similar rostral proportion index with bottlenose dolphins - an RPI of 2.4-2.6, in other words - a rostrum (excluding the tip made out of just the premaxilla) that is about 2.5 times longer than it is wide at the base. This is suggestive of a generalist diet - not specialized for anything in particular, but permitting feeding on large and small prey. What about suction feeding? Xenorophus clearly has no degree of tooth loss, and an RPI that is too high for specialized suction feeding. A single hyoid bone from CCNHM 168 is rod-like, nearly identical to basilosaurids - differing from the widened, spatulate hyoids of modern delphinoids and ziphiids. While we know that some xenorophids like Inermorostrum were suction feeding specialists - available evidence indicates that Xenorophus was not a specialized suction feeder (despite probably being able to generate some suction like all toothed whales).

Vertebral anatomy and locomotion in Xenorophus

Very few stem odontocetes are known from vertebral columns - and, of the few that are, I've published most of them - Albertocetus, Ankylorhiza, and now, Xenorophus. There are two good Xenorophus specimens with much of the vertebral column preserved - CCNHM 1077 and ChM PV 5022. CCNHM 1077 has more of the caudal and thoracic vertebrae preserved, and ChM PV 5022 has a complete thoracic series. These specimens give us a count of seven cervicals, ten thoracics, ten lumbars, and at least a half dozen caudal vertebrae. The neck of Xenorophus is long - measuring approximately 40-45% of the length of the skull, and suggesting considerable more mobility than in extant odontocetes: the cervicals are not changed very much from the basilosaurid condition.

Skeletal reconstruction of Xenorophus sloanii, based chiefly on CCNHM 168 and CCNHM 1077. Artwork by yours truly. From Boessenecker and Geisler (2023).

In the caudal (tail) vertebrae, we found that there was no evidence of an external narrowed caudal "peduncle". In most modern cetaceans, with a couple of exceptions, the tail stock is very narrow and much higher (dorsoventrally) than wide - in many groups this results in vertebrae that are somewhat narrower than they are tall. This narrow peduncle allows the tail to slice through the water and making most of the force generated by up/down movements of the caudal fluke to be localized on the fluke itself - also permitting greater dorsoventral movement of the flukes. Basilosaurids have vertebrae in this region that are wider than long, so Mark Uhen (2004) suggested that Dorudon atrox may have had a sirenian-like tail stock. The few caudal vertebrae of Albertocetus meffordorum are approximately as wide as tall, and so in 2017 we proposed a similar hypothesis - that xenorophids lacked a narrow peduncle. The very complete vertebral column of Ankylorhiza* confirmed this, and is now confirmed again in Xenorophus. Ankylorhiza is of course not a xenorophid, but a more derived agorophiid-grade odontocete. A narrow peduncle is a derived trait, and so we (Boessenecker et al., 2020) proposed that this adaptation evolved multiple times - or, at least twice: once within mysticetes and once within crown odontocetes. This suggests that Xenorophus was not quite as strong or fast a swimmer as most extant odontocetes.

Observations of the vertebral column don't end there, though. We also took measurements of CCNHM 1077 to produce what I have started lovingly calling "Buchholtz diagrams" after Dr. Emily Buchholtz who started using them 20 years ago. It takes quite a bit of staring at these before you see the forest through the trees, and once you start to get them, they're deceptively simple. It also requires a bit of non-intuitive knowledge of what vertebral dimensions confer to bending of the vertebral column. Shorter, hockey-puck like vertebrae result in a stiffer column despite having more joints - and perhaps the addition of more intervertebral disks results in more stored elastic energy. This confers faster swimming speeds and characterizes many delphinid dolphins, phocoenid porpoises (especially Dall's porpoise, Phocoenoides dalli), as well as lamnid sharks and ichthyosaurs. Elongate vertebrae confer slower swimming speeds and perhaps greater manueverability - this is generally the ancestral condition in all marine tetrapod groups, though it also is present in swordfish, marlins, and sailfish - some of the fastest marine vertebrates (however, as I understand it, they are fast in bursts). These are generalizations, and ignores changes in vertebral proportion throughout the column. So, what happens when vertebrae change shape?

Within cetaceans, Buchholtz (2001) came up with a three-fold division of vertebral dimension patterns. Pattern 1 cetaceans have vertebrae of similar proportion throughout the column, with some anteroposterior shortening in the lumbar/caudal series, no narrowing of the peduncle, and based on modern species, are the least maneuverable; up/down movement (undulation) occurs nearly throughout the vertebral column. Pattern 1 species include modern and fossil mysticetes, the sperm whale (Physeter), archaeocetes, and probably Albertocetus. Pattern 2 cetaceans have a long series of anteroposteriorly compressed vertebrae in the anterior tail and lumbars that is somewhat stiffened, developed as a stiffened 'peduncle'; much of the up/down undulation is localized within the vertebral column to the posterior thoracic vertebrae and anterior lumbars; there is moderate narrowing of the tail stock and a bit of an external narrow peduncle is developed. Pattern 2 species include beaked whales (Ziphiidae), white whales (Monodontidae), the four extant river dolphins, false killer whale (Pseudorca), and of course, Ankylorhiza (though likely lacking a narrow peduncle). Pattern 3 cetaceans have hockey puck shaped vertebrae that are circular to oval and much taller than they are long (anteroposteriorly) and secondary increase in vertebral length in the anterior caudal vertebrae, suggesting that these function as an "elbow" in the vertebral column; these are adaptations for very rapid swimming with a stiffened torso. Pattern 3 species includes most Delphinidae including Orcinus, Steno, Tursiops, Lagenorhynchus, Lissodelphis, as well as extant Phocoenidae.

"Buchholtz diagram" - aka vertebral dimension plot - for CCNHM 1077, the most completely preserved single specimen of Xenorophus sloanii. From Boessenecker and Geisler (2023).

Xenorophus seems to be a Pattern 1 species, though bordering on some Pattern 2 adaptations. The posterior lumbar vertebrae lengthen and also become dorsoventrally deep and large in size, along with the anterior caudals - suggesting a degree of Ankylorhiza-like stiffening of the tail stock. Thoracic vertebrae are wider than long, which is a primitive Pattern 1 feature. Though some of the increases in vertebral length, width, and height are more extreme than in Ankylorhiza, there is no trend towards foreshortening of the vertebrae in the tail stock, a major feature of Pattern 2 swimmers. In comparison to other medium to large size cetaceans from the Oligocene of South Carolina, Xenorophus sloanii was a faster and more efficient swimmer than Coronodon, but less so than Ankylorhiza tiedemani.

Dental asymmetry in Xenorophus sloanii: measurements are in millimeters, whichever side is further anterior. For example: in CCNHM 168, all of the teeth on the right are shifted anteriorly relative to those on the left, by 2.1 to 8.5 mm. From Boessenecker and Geisler (2023).

Cranial, Dental, Mandibular, and Vertebral Asymmetry in Xenorophus

Sometime during the pandemic I was on the phone with my coauthor Jonathan Geisler and we were talking about the oddness of xenorophid skulls, and we thought they were asymmetrical - but it was just a gut feeling. "Something about when you look at their skulls in anterior view... they just look wrong". With this in my mind, I decided to look for more concrete evidence. Sometimes, you just have to start putting lines down over photographs to see if anything is violating basic symmetry. The problem is, it was difficult to even know where these landmarks were supposed to be, given what we eventually found out. At first, I noticed that the palate and teeth were asymmetrical - and these made it into my 2020 SVP talk, which was of course recorded ahead of time and uploaded to the SVP conference webpage rather than delivered in person.* While I was working on the talk, I noticed that the teeth of CCNHM 168 and 104 were all wonky - most of the postcanine teeth right are shifted anterior to the ones on the left, by at least a few millimeters and in some tooth positions over a centimeter! What the hell?! Nobody had ever documented that in a fossil cetacean before. After some more looking, it turns out that many basilosaurids have asymmetrical dentitions - and nobody had really noticed before!** What could drive the asymmetry in these cetaceans? My German colleague Dr. Julia Fahlke published an interesting article in 2012 on asymmetry in Basilosaurus, noting that the rostrum was twisted longitudinally, bent to the left, and that the thinnest parts of the pan bones of the mandibles were asymmetrical, with one shifted further anterior than the other (more on that below). I suspected immediately that the asymmetrical teeth are likely driven by the bending of the rostrum to the left side. But what about Xenorophus? Surely, its rostrum was not also bent - that had been observed only in basilosaurids so far.

*The 2020 conference is actually what killed online conferences for me. Surely I can do an online conference at the same time I have a full teaching load! Of course, the majority of my colleagues were in other states and not back in the classroom - we had just been forced back into the classroom by the school administration (because red state) and the Q&A session was scheduled for a time during my first week of labs. I was already terrified of getting Covid, and I noticed that virtually everyone on the zoom call was unmasked - because they were at home. I couldn't speak, because I was in class. I typed out a couple responses and only had a couple of questions before Q/A moved on. The remainder of the week I got considerably more stressed as I needed to tend to my teaching but also felt a bit worried that I was neglecting my responsibility to attend the conference - and decided to just watch all of the talks on the weekend. The stress of this stupid experience made me realize I could never juggle an online conference, and I'll never attend one again. I know that they're great and everything for folks who can't travel, but I just can't do both. I'm not teaching any more, so maybe I can give it another go.

**Doesn't really surprise me, to be honest. Much of the previous work on basilosaurids, with some notable exceptions, has not focused on cranial anatomy. And, in the few basilosaurid whales with good, detailed cranial and dental descriptions - the skull is quite asymmetrical, and perhaps exaggerated by burial compaction - e.g. Cynthiacetus peruvianus, described well by Martinez-Caceres et al. 2017.

Asymmetry of the palate in Xenorophus sloanii: note the left-right asymmetry of the maxillopalatine suture, median palatine suture, and the exposure of the vomer. mx = maxilla; pa = palatine; v = vomer. From Boessenecker and Geisler (2023).

Even before this, I had noticed the asymmetry of the palatine bones. The right palatine is always larger than the left in Xenorophus spp. and the maxillopalatine suture is shifted further anteriorly on the right, by 5-15 mm, and the suture is also nowehere close to symmetrical - unlike all other stem odontocetes I've looked at (Ankylorhiza, Simocetidae, Waipatiidae, Squalodon, etc.). This asymmetry of the palatines is shared with Albertocetus, and the right palatine is also longer/larger than the left. It doesn't stop there, though: the vomer is asymmetrical, with a very elongated trapezoidal shape. The vomer exposure in the palate becomes anteroposteriorly longer during growth and the underlying maxilla 'unzips', but asymmetrically so: the left maxilla seems to be emarginated on its lateral side to expose the vomer posteriorly, and anteriorly, it's the right maxilla. But it doesn't stop there! In adults, the median palatine suture is shifted to the left of the midline, and is actually bowed somewhat in specimens like CCNHM 1077.

Skulls of Xenorophus sloanii in anterior view. Something just seemed off... From Boessenecker and Geisler (2023).

Rostral deviation to the left in Xenorophus sloanii. From Boessenecker and Geisler (2023).

I was suspicious about the rostrum given Jonathan's comments over the phone that something just "doesn't look right". When I looked down the tip of the rostrum (in anterior view), you can't really line up everything properly - at no single angle did the skull look symmetrical. In the photo above, I settled on shooting down the axis of the rostrum. So, when I drew a line on these skulls along the midline of the braincase - from the middle of the occipital condyles through the nasals - I noticed that in every specimen, that line went to the right of the midline of the rostrum. Could it be due to burial deformation? What about the specimens being improperly assembled during "puzzle piecing"? Perhaps, but there are several important problems with each of these. First, specimens in the Ashley Formation are typically three dimensionally preserved, and there's not much in the way of structural shearing here. Chandler Bridge Formation specimens are frequently highly fractured with fragments separated from one another. These specimens are cleaned, one fragment at a time (or occasionally screenwashed from goopy sediment), dried, and glued together one joint at a time. This is occasionally done for Ashley Formation specimens when the limestone 'marl' is quite soft. There is one specimen that I think has been deformed naturally: the Xenorophus simplicidens holotype (CCNHM 8720), the rostrum of which is somewhat deformed and actually bends off to the right side by a few degrees - owing to many relaxed fractures infiltrated with silt. However, all other skulls complete enough to evaluate bed about 1-5 degrees to the left. What's noteworthy is that these skulls were preserved and prepared differently. Specimens CCNHM 104, 168, and the X. sloanii holotype (USNM 11049) have some hairline fractures but were basically prepared traditionally through matrix removal and stabilization, and were not fractured into a zillion pieces. The Xenorophus simplicidens paratype, ChM PV 4823, and possibly referred X. sloanii skull ChM PV 7677, were puzzle-pieced together - and both still point off to the left side. Further, in ChM PV 4823, there are some artificial gaps in between the left and right halves of the rostrum, which suggests to me that it was reassembled and the preparator made their best attempt to 'force' it into being symmetrical - and ultimately was still unable to do so.

Growth changes and asymmetry of the vertex in Xenorophus sloanii. Apologies for showing this one again. From Boessenecker and Geisler (2023).

Some other details are evident in the skull. In adult specimens like CCNHM 1077, 168, and ChM PV 5022, the sagittal crest is asymmetrical and actually tracks to the left - as if it's been rotated clockwise. This suggests that during growth the temporalis muscles are asymmetrically developed, with the stress and strain from biting resulting in an asymmetrical muscle attachment ridge. The antorbital fossae - large basins on either side of the rostrum, adjacent to the bony nares - are asymmetrical in Xenorophus. These basins are unique to the xenorophids and are actually a synapomorphy of the family, but there are some subtle ways in which they vary. In Echovenator and Cotylocara, the fossae are symmetrical. But in both species of Xenorophus, they are asymmetrical. In Xenorophus sloanii, the left fossa is more deeply excavated, anteroposteriorly longer, and transversely wider than on the right. Curiously, in the Xenorophus simplicidens paratype (ChM PV 4823), the opposite is true - the right fossa is longer than the left! It's unclear owing to incompleteness if it was wider, however. For a while I thought that perhaps the asymmetry of the palatines was linked to the asymmetrical fossae with a longer palatine underlying the shorter fossa and vice versa in Xenorophus sloanii. However, once I realized that the rostrum was bent to the left, it made sense: the palatine extends further underneath the right half of the rostrum as the entire complex has been rotated counter-clockwise (in dorsal view).

The mandibles of Xenorophus sloanii in dorsal view, showing asymmetry of the lower dentition. Also, you can pretty clearly make out the missing teeth in CCNHM 168. From Boessenecker and Geisler (2023).

Remember the asymmetry of the teeth? What about the rest of the lower jaw? Unfortunately, there's only one specimen with mandibles, and those mandibles do have a couple of pathologies - so it's difficult to reconstruct and measure how offset the teeth are. However, they are quite clearly offset as well. What's far more damning, however, is the relative position of the posteriormost tooth. When I measured from the mandibular condyle (jaw joint) to the back of the last tooth, the distance on the left mandible is an entire centimeter shorter than on the right! Think about it: if you rotate the rostrum to the left, you're stretching the right side and shortening the left.

Rampant asymmetry throughout the skull, mandibles, dentition, and even the vertebral column of Xenorophus sloanii. I wouldn't go so far as to say that the entire vertebral column was asymmetrical - but in this specimen, CCNHM 168, every single vertebra is asymmetrical in ways that cannot be explained by burial (diagenesis).

But we really aren't even close to done with the asymmetry - because it continues into the postcranial skeleton. Yes, even the vertebrae are asymmetrical! Virtually all of the cervical vertebrae have transverse processes that are somewhat differently shaped left to right - having either a different outline, projecting in a different direction, or being longer on one side. This is most extreme in the sixth cervical, frequently identifiable in land mammals and archaic cetaceans because of the long, ventrally directed processes. In THREE different specimens of Xenorophus (CCNHM 168, above, CCNHM 1077, and ChM PV 5022), the left process is more vertical than the right, longer from base to tip, and also more greatly expanded in lateral view (by a half centimeter) - see the figure above. The atlas vertebra is also wedge-shaped - the left side is a half centimeter longer than it is on the right, which means that the anterior and posterior articular surfaces seem to diverge at an angle of over 4 degrees. This suggests that the entire braincase is canted about 4 degrees to the right. Combined with the bending of the rostrum, this suggests that the entire osteological midline is a zig zag. Unfortunately, given that the entire top of the braincase is slightly off kilter, it's difficult to use any landmarks on the skull to test this hypothesis - but, more on this shortly. In addition to this, the neural spines of the thoracic and lumbar vertebrae are also asymmetrical - in ChM PV 5022, CCNHM 168, and CCNHM 1077, each vertebra with complete neural spines is either tilted to the left and/or twisted a little bit along its vertical axis, and in the same direction (clockwise in dorsal view) - and most vertebrae have evidence of both. The transverse processes in the lumbars are mostly broken, but there is a slight difference in orientation in CCNHM 168 where they are well-preserved.

Press release image of the asymmetrical skull of Basilosaurus isis reported by Fahlke et al. (2011), showing the bending of the rostrum to the left (our right) and twisting of it along the long axis. Photo credit: Julia Fahlke.

Asymmetry of the "pan bones" in Basilosaurus isis showing differences in the thickness of the wall of the mandibular fossa/foramen. From Fahlke et al. (2011).

So, what gives? Why is there such an extreme degree of asymmetry? The postcranial asymmetry is odd, but there may be a modern analog: the Ganges river dolphin, Platanista gangetica, engages in side-swimming, and maybe Xenorophus did something similar. However, there's no data available indicating that the postcrania of this species are asymmetrical, and no a priori reason to infer that side swimming is any different than swimming dorsal-up - so I don't really buy that. Since we already know the rostrum is bent, perhaps the vertebral asymmetry is a consequence of cranial asymmetry imparting unequal left/right drag onto the head - pretty obvious if the snout sticks off to one side. So, let's start with the head. Rostral bending and twisting is already documented in basilosaurids and some protocetids by Fahlke et al. (2011), who also determined that the 'pan bones' of the mandible are asymmetrically positioned: the thinnest part of the left mandible is approximately 10 cm further anterior to the thinnest zone on the right, perhaps indicating that the mandibular fat pads are positioned differently.* This study proposed that cranial asymmetry is driven by asymmetrical hearing in late archaeocetes as an adaptation for improved directional hearing - and that this asymmetry was lost in Neoceti as underwater hearing continued to improve. [A quick refresher: sound waves tend to travel through water and bone at more or less the same speed, arriving at each ear simultaneously. Mammalian directional hearing relies on being able to calculate very slight differences in 'arrival time' of sound waves between your two ears - interpreted by your brain as a direction of the sound wave. Underwater, this is not possible - so cetaceans have evolved a series of adaptations to acoustically isolate each ear from the rest of the body, funneling left/right sound waves into the fat pads, channeled through fat channels directly to each middle ear - thereby restoring directional hearing. Fahlke et al. (2011) proposed that the asymmetry in the skull and jaws was a sort of analog to the hearing system in owls, which famously have one ear placed higher than the other - this lets owls 'zero in' on the direction of even very quiet sounds in the dark of night. In Fahlke's hypothesis, basilosaurid whales did something similar after acoustically isolating their inner/middle ears.

*Ted Cranford and others (2008) demonstrated, however, that sound likely travels through the "gular" pathway - through the throat and into the medial side of the fat pad where it is exposed by the cavernous mandibular foramen (e.g. not roofed over by bone medially) and not laterally through the pan bone as originally proposed. They indicated, as others had, that sound waves probably cannot travel through the pan bone, no matter how thin it is, owing to the somewhat higher density of the bone - this is called acoustic impedence, and would cause much of the sound signal to bounce off the bone rather than travel through it. This would explain why the mandibular foramen is so large in cetaceans - keeping a bony lid off of the fat pad. In Basilosaurus isis, the thinnest part of the pan bone is in completely in front of the mandibular foramen - suggesting that this part would not really receive sounds, and because the mandibular foramina in the left and right mandibles look nearly identical, this mode of asymmetry may not necessarily indicate asymmetrical hearing.

We largely agree with this hypothesis, though Fahlke et al. (2011) did not really explain why the snout was bent or twisted as a consequence. We found that the "pan bones" in Xenorophus are probably asymmetrical in orientation, with the left posterior mandible being somewhat more anteroposterior facing and the right being posteromedially facing. In other words, the mandibular fat pads have been rotated counter-clockwise in dorsal view. Evidence from the vertebral column of CCNHM 168 suggests it's therefore not the rostrum that's twisted - it's the braincase! In sum, reorientation of the posterior mandibles drove asymmetry of the posterior skull, and the asymmetry of the rostrum resulted in stronger hydrodynamic forces (e.g. drag) that drove asymmetrical muscles, which resulted in asymmetrical muscle attachments in the vertebral column.

Phylogenetic Placement of Xenorophus

As in previous studies, Xenorophidae are recovered in our analysis as one of the earliest diverging clades of Odontoceti. Only two peculiar early toothed whales show up more basally - Mirocetus riabinini, an unusual toothed whale from the Oligocene of Azerbaijan, and Ashleycetus planicapitis from the Ashley Formation. Mirocetus is positioned as the basalmost odontocete, and Ashleycetus is positioned as sister to the Xenorophidae. While the skull of Ashleycetus is well-preserved, it is missing teeth and earbones, and the skull of Mirocetus is poorly preserved with uncertain sutures and no earbone morphology that can really be scored - meaning that interpretation of Mirocetus is challenging. Limited codings for these fossils mean that each tends to float around a bit on different variations of this same matrix (e.g. Sanders and Geisler, 2015; Velez-Juarbe, 2017, 2023).

Regardless, these are singletons missing lots of character data, and the Xenorophidae are markedly different in several ways such as 1) their diversity, 2) consistent placement as a major clade at the base of Odontoceti (e.g. existing as a bit of an 'anchor point' for these other Oligocene dolphins that float around a bit on the tree), and 3) their anatomical distinctiveness that leads to well-resolved relationships within the clade Xenorophidae. Furthermore, this is a bit of a preservational issue, but for several genera of xenorophids - Albertocetus, Echovenator, and Xenorophus - there are multiple specimens known for each taxon (a massive understatement) and these taxa are known from nearly all cranial, earbone, and dental characters (and even most of the "singleton" taxa like Cotylocara are as well).

A simplified version of our phylogenetic tree showing the new clades Amblyoccipita and Stegoceti. From Boessenecker and Geisler (2023).

New Odontocete Clades

There have been a proliferation of fossil toothed whale genera and families, especially so on the stem group, over the past 20 years or so. However, we haven't had any 'suprafamilial' clades to help break this up - so we thought of two possibilities, and defined these clades in our paper.

The first is the Amblyoccipita. This can be thought of as the most inclusive group of toothed whales that excludes the Xenorophidae - the most basally positioned group of odontocetes. Amblyoccipita means "round braincase" in Greek, referring to the rounded supraoccipital shield in these dolphins and contrasting with the primitive triangular vertex seen in Xenorophidae. Amblyoccipita includes most simocetid dolphins, agorophiid-grade dolphins, along with waipatiid-grade and squalodontid-grade dolphins - and of course, Crown Odontoceti. This clade had been begging to be named for 20 years, and saying "the most inclusive odontocete clade excluding xenorophids" has gotten a bit tiring.

The second clade is the Stegoceti, meaning "roofed cetaceans" in Greek. This refers to the intertemporal region of the skull being transversely expanded so that the temporal fossa is partially or completely 'roofed over' in dorsal view. This clade excludes all odontocetes with a narrow intertemporal region that is round in cross-section - so the Xenorophidae as well as the Simocetidae and a few others like Ashleycetus and Mirocetus - and includes the "Agorophiidae" (e.g. Ankylorhiza, Agorophius) and all later stem odontocetes.

The basic definitions of the new clades. The Amblyoccipita are all odontocetes with a rounded vertex (blue line) - in most xenorophids, the vertex is pointed (though Cotylocara and Echovenator have secondarily converged on the rounded morphology). In simocetids like Olympicetus and Simocetus, agorophiids like Agorophius and the possible agorophiid Ankylorhiza, waipatiids, squalodontids, and nearly all Miocene to modern odontocetes in the crown clade, the anterior edge of the occipital shield is rounded. The Stegoceti include agorophiid-grade odontocetes like Ankylorhiza which have the intertemporal region roofed over by the supraorbital process - the posterior end of which is shown in red. Waipatiid and squalodontid-grade odontocetes, and all Crown Odontoceti have a wide intertemporal region that is 'roofed' over.

Other odontocete clades need to be named, but the later-diverging parts of the odontocete stem are much less clearly resolved. However, further exclusive clades defined by the exclusion of "agorophiids", "waipatiids", and "squalodontids" are worth naming in the future. Further, it seems possible from our phylogeny that single-rooted teeth may have evolved just outside the crown group, and so a "Homoceti" or "Homodontoceti" might be nameable at some point.*

*One problem is that different matrices give different results. Smaller matrices with fewer characters and fewer taxa often place waipatiids, squalodontids, and other oddballs with clearly double rooted teeth into the poorly defined "Platanistoidea" and well into the crown group, though I don't have much confidence in these hypotheses. I personally think single rooted teeth is likely to be ancestral for the entire crown group - but this is the essence of differences in phylogenetic philosophy and parallelisms/convergence.

It's worth stressing here that these two clades are very commonly recovered in nearly all phylogenetic analyses of stem odontocetes. The only analyses that tend not to recover these clades have only coded for a few stem odontocetes and therefore simply don't have enough taxa to reflect these relationships. Given that we've seen these clades again and again and again in 20+ years of phylogenetic analyses of early odontocetes, we felt it was time to name them.

Evolution of Body Size in Odontoceti

I was prompted to investigate the evolution of body size across the archaeocete-neocete transition because many early mysticetes and odontocetes are much smaller than your average basilosaurid.* We did find some support for this - the mean archaeocete body size, represented by skull width as our proxy for body size - is somewhat larger (~40 cm skull width) than in odontocetes, which start off around 20 cm and the mean rarely exceeds 25 cm. This is a bit of a modest change, but it's also the average of each - the minimum body size of odontocetes is considerably smaller, around 10-15 cm, than the equivalent minimum in basilosaurids - around 20 cm or so (and even these are outliers among basilosaurids).

*Sizes are more congruent with protocetids - however, protocetids are semiaquatic and therefore likely have a maximum body size imposed upon them by virtue of hauling out on land - just like your average pinniped is on the whole much smaller than your average cetacean.

The story with toothed mysticetes is a bit more complicated - complicated by none other than Llanocetus denticrenatus, the largest - and earliest - toothed mysticete. It's got a skull much larger than any basilosaurid (skull width almost a meter), though I imagine it was probably considerably outsized in body length by Basilosaurus cetoides, Basilosaurus isis, and Perucetus colossus (not included in our study). However, if you ignore Llanocetus as a bit of an outlier, toothed mysticete mean body size is otherwise much smaller than basilosaurids - see for example the relatively small species of Fucaia, Chonecetus, Mammalodon, and even every single species of Aetiocetus is considerably smaller than your average basilosaurid.

Evolution of Polydonty in Cetacea

Xenorophus is quite interesting owing to the fact that it is already polydont despite being one of the earliest diverging odontocetes. Polydonty refers to the evolution of additional tooth positions beyond the primitive number for placental mammals - 11 per quadrant, for a total of 44. Humans and other old world primates have a total of 32 (we've lost a pair of incisors, and two different premolar positions). Dolphins are well-known for their toothy grins, with many species possessing 20-40 teeth per quadrant. The La Plata river dolphin, Pontoporia blainvillei, possesses between 50 and 60 teeth per quadrant - the highest tooth count of any modern mammal. The extinct dolphin Parapontoporia from the Miocene-Pliocene of California has the highest tooth count of any cetacean ever, with approximately 90 teeth per quadrant - for a blistering total of about 360 teeth! (I've been told Pomatodelphis might exceed this, but am unaware of any specimens conclusively beating this number). Modern baleen whales of course have no adult teeth, but incredibly have polydont fetal dentitions that are resorbed. So, there's abundant evidence of polydonty in modern odontocetes and extinct crown odontocetes - but when did this start? And did polydonty evolve once or multiple times within Neoceti? Let's take a closer look at whale ancestors.

Ancestral character state reconstruction of polydonty from our analysis. Note that we're ignoring the addition of a single postcanine tooth here, as this does seem to fluctuate a bit within Oligocene cetaceans. Under one hypothesis, polydonty evolves once near the base of Odontoceti (P1) and under another, it evolves convergently within the Xenorophidae and the Stegoceti (P2). This is of course in addition to the polydonty that is evident within certain toothed mysticetes (Coronodon, Aetiocetus) and extant embryonic mysticetes.

Most archaeocete whales like protocetids have 11 teeth in each quadrant, and basilosaurid whales interestingly have lost one upper molar (for a total of 10). The toothed mysticete Coronodon has 11 upper teeth, but a total of 12 mandibular teeth - indicating that early mysticetes developed incipient polydonty very, very early. This seems to indicate that the ancestral condition for the clade Pelagiceti (Basilosauridae + Neoceti) is to have one additional tooth in the mandible - and evidently, losing an upper tooth is a basilosaurid feature. So, Coronodon seems to have evolved one additional tooth position in each quadrant versus basilosaurids. Other toothed mysticetes have only modest increases in tooth count, with 1-3 additional teeth present in species of Aetiocetus and basilosaurid-like tooth counts in Mammalodon and Janjucetus.

On the other hand, Xenorophus has 13 teeth per quadrant, and one specimen even has 14 teeth - CCNHM 168, for a total of 10 postcanine teeth instead of the typical 7 present in placentals. Other xenorophids have tooth counts all over the place, with zero in Inermorostrum and over 23 in one unnamed xenorophid (ChM PV 4746). Remarkably, within this family, not only is there polydonty but it seems as though there's no constraint on the number of teeth and quite a bit of variation already - in stark contrast to the cookie-cutter dentition of their basilosaurid ancestors.

But how did polydonty evolve? Several hypootheses have been proposed. Ewan Fordyce proposed, based on an unusual 'squalodontid' jaw from New Zealand with alternating small single-rooted and large double-rooted teeth, that the milk dentition and adult dentition merged into one generation, with milk teeth being placed in between the adult teeth. This addition of the two tooth sets could have led to an increase in tooth count. However, in my opinion this specimen with supernumerary teeth is anomalous and perhaps has a developmental problem that is not evolutionarily informative. I do think there is more of a story here regarding monophyodonty, but I don't necessarily think the two are as closely linked: Fordyce's hypothesis is elegant, as it would link polydonty and monophyodonty together - but I don't think it's supported at present, especially if our 'P2' hypothesis for delayed and convergent polydonty is correct. It also cannot explain early odontocetes (and mysticetes) with just a couple of additional tooth positions.

There aren't that many other treatments of the mechanics of the evolution of polydonty - the underpinning genetics haven't yet been investigated, to my knowledge. But - intuitively, you could just add tooth positions onto the very back end of the dentition - this seems a viable hypothesis, as heterodont odontocetes don't seem to have an increased number of incisors (still three teeth in the premaxilla) so addition of teeth at the anterior end seems unlikely - though perhaps teeth are being added somewhere else - in the middle?

A developmental hypothesis for homodonty (not polydonty - but keep reading) was presented by Armfield et al. (2013), who looked at Hox genes in the dentition of mammals. In embryonic/fetal mammals, they found that the gene Bmp4 is expressed in the zone where incisors are formed, and the gene Fgf8 is present where premolars are being formed. In some modern mammals, where these genes overlap, a canine is formed, and in experiments in mice, unicuspid canine-like teeth are formed if these two fields are made to overlap. In extant odontocetes, these two genes overlap considerably with Bmp4 expression throughout the entire toothrow - producing homodont teeth. Interesting!

It's important to note that homodonty - teeth all of the same shape - and polydonty - increased tooth count - are two totally different things, and have different evolutionary origins. Most stem odontocetes - including Xenorophus - are still heterodont, even if polydont. But - remember how I mentioned that tooth count varies within Xenorophus? Specimen CCNHM 168 has an additional tooth position. However, if you count the clearly double-rooted teeth, all specimens have five with roots that split outside the socket and a relatively complex crown, and an additional sixth double rooted tooth just in front with a slightly simpler, smaller crown. The additional tooth in CCNHM 168 is somewhere in the anterior postcanines - somewhere between PC1-4. In other words, there are four single-rooted anterior cheek teeth in CCNHM 168, and only three in other specimens like the holotype, ChM PV 7677, and CCNHM 104. This just so happens to be the region where Fgf8 and Bmp4 overlap - though we didn't discuss this in the paper, I suspect that the region of overlap in Xenorophus is restricted to the anterior third or half of the postcanine dentition, given that these teeth look just like the canine, with subtle changes posteriorly. So - we still don't know what the mechanism is, but we proposed that based on this 'polymorphism', teeth in the middle of the toothrow are added, rather than at the posterior end.

A gray whale in the Purisima Formation?

2026-06-19T09:24:03.957-07:00

The unusually straight, somewhat flattened mandibles of the gray whale Eschrichtius robustus - skeleton on display at the Charleston Marine Life Center in Charleston, Oregon (not THAT Charleston!). Photo by the author.

I've been studying fossil baleen whales from the Purisima Formation of northern California for about twenty years now, and I am always learning new things. So far, baleen whales (mysticetes) from the Purisima Formation tend to belong to three families: the Balaenopteridae (rorquals), Cetotheriidae (dwarf whales, mostly my old friend Herpetocetus), and the Balaenidae (right whales). There are about a dozen species from the Purisima, over half of which are balaenopterid whales. Balaenopterids, or 'rorquals', include the blue, humpback, fin, minke, and sei whales - all the species with many elongate throat pleats. including archaic forms like Norrisanima miocaena, "Balaenoptera" cortesi var. portisi, and Parabalaenoptera (originally reported from the Santa Cruz Mudstone of Marin County a bit further north). There are also some more derived forms, like the minke whale like species Balaenoptera bertae, which I named when I was a Ph.D. student. The Purisima Formation is latest Miocene to late Pliocene in age - roughly 7-2 million years old - and most other marine rocks elsewhere dating to the same time period are also dominated by balaenopterid whales.

The ~five meter long, strongly arched mandibles of "Hope" the blue whale, Balaenoptera musculus, at the Natural History Museum in London. Photo by author.

I do plan on doing an entire blog post on the fossil record and evolution of gray whales, but a short summary is warranted here. Gray whales are in the family Eschrichtiidae, and today, there is only a single species - Eschrichtius robustus - which lives only along the Pacific coast of North America. In the past, Eschrichtius robustus also inhabited the western North Pacific as well as the North Atlantic. There are a handful of fossil gray whales. The oldest is Archaeschrichtius ruggerioi, from the upper Miocene of Italy, dating to about 7.5-11 Ma. This specimen is based on an isolated mandible with an unusual double coronoid process. I'll talk about the difference between balaenopterid and eschrichtiid mandibles later in this short article. A relatively small gray whale, originally named Cetotherium gastaldii in the 1880s from Italy, was renamed Eschrichtioides gastaldii in 2005 by Michelangelo Bisconti. This specimen has a skull that is slightly more 'primitive' than the modern gray whale - and it dates to the early Pliocene (~4-5 million years old). The only other extinct genus of gray whale, Glaucobalaena, is quite fragmentary - consisting only of paired left and right chunks of the basicranium - is from the late Pliocene of, you guessed it - Italy. The only named extinct eschrichtiid outside of Italy is Megapteropsis robusta, a chimaeric assemblage of fossils named by P.J. Van Beneden in 1872. One of the specimens is a rather well-preserved mandible, which Van Beneden figured in excellent detail. There is a well-represented but unnamed species of gray whale from the late Pliocene (2-4 million year old) San Diego Formation, known from multiple skulls and skeletons. This taxon was misidentified as a balaenopterid whale for a long time - and since gray whales and balaenopterids are sister taxa and forma clade, Balaenopteroidea, it's not surprising that some fossils would more closely resemble balaenopterids. As it happens, the genus Eschrichtius is quite derived in many ways.

Another putative gray whale, Gricetoides aurorae, was named from the Pliocene Yorktown Formation at the Lee Creek Mine. The holotype is a skull that very much looks like a regular balaenopterid, but the bulla is clearly from a gray whale. However, they are not associated. The skull, I think, is from an extinct balaenopterid, and I won't discuss it further here - other than to say that the bulla does record a gray whale in the Pliocene rocks of the western North Atlantic.

The remaining fossils of gray whales are all from the genus Eschrichtius. There's a late Pliocene mandible fragment of Eschrichtius from Belgium, a late Pliocene skeleton of Eschrichtius sp. from Japan, and an extinct species in the modern genus, Eschrichtius akishimaensis, from the early Pleistocene of Japan. Lastly, there are a few fossils from the Pleistocene of California - my colleague Cheng-Hsiu Tsai wrote a paper that I coauthored where we reported a tympanic bulla of Eschrichtius from the early Pleistocene Rio Dell Formation of California, which still is the oldest record of the modern genus from the eastern North Pacific. There is also a complete skull and partial skeleton of a gray whale, likely Eschrichtius robustus or a closely related extinct species yet to be named, from the late Pleistocene San Pedro Sand of Los Angeles. I'll summarize the eschrichtiid fossil record in more detail in a later post.

A typical mysticete from the late Miocene and Pliocene of California: the extinct balaenopterid whale Parabalaenoptera baulinensis, from the upper Miocene (~8 Ma) Santa Cruz Mudstone of Bolinas in Marin County, California. Photo by the author.

Complete skulls of fossil gray whales are quite rare, being known pretty much from Italy and San Diego. I've been paying attention to more fragmentary remains for a long time - the earbones are quite distinctive. Unfortunately, the fossils of some early balaenopterids share some features in common with gray whales, so it can be difficult to distinguish between the two. One such feature is the fenestra rotunda on the periotic bone - in Eschrichtius robustus, this foramen is open dorsally, which until recently, was thought to be unique to Eschrichtius. In all other cetaceans, this foramen is circular and surrounded by bone. Recently, a paper by Bisconti reported the periotic anatomy of the blue whale, Balaenoptera musculus, and reported that an earlier specimen was probably a misidentified fin whale. Turns out, the blue whale also has an open fissure-like fenestra rotunda. And, so do many early balaenopterids. Are some of these early balaenopterids actually outside the balaenopteridae? Are some actually gray whales, or do they diverge earlier? Indeed, there are a couple of Eschrichtius-like periotics from the Purisima Formation - but these happen to match the periotics of a small balaenopterid known from more complete skulls in the San Mateo Formation of southern California, and may possibly represent Kennedycetus pericorum from Baja California (which I saw in person at UABCS in La Paz this January). The tympanic bulla is a little more reliable, and while gray whale bullae are not rare in Pliocene rocks of the Atlantic coast - uncommon, I'd say - I've not found any obvious eschrichtiid bullae in the Purisima Formation.

The mandible of the minke whale, Balaenoptera acutorostrata, with cross sections in approximate location relative to the above diagram. Modified from Demere (1986).

The mandible of baleen whales is occasionally overlooked by paleocetologists, but generally the anatomy mandible really conforms to family-level clades. Right whales, for example, have strongly bowed mandibles with massive elevated condyles that look like basketballs at the end of the mandible, lack a coronoid process, and are twisted dramatically at the anterior tip; these mandibles are also quite thick and have a nearly circular cross-section for most of their length. Right whale mandibles can be quite large - 1.5 meters, up to about 5 meters in length. Cetotheriids are generally quite small (1-2 meters), but have a slightly bowed mandible and often an elongate, low, and laterally hooked coronoid process; the cross-section is usually oval. Balaenopterids look quite similar to cetotheriid mandibles, but differ in a couple ways - the mandibles may be as small as 1.5 meters, and up to 6 meters in the blue whale - but in the fossil record, usually smaller than three meters. The cross-section is D-shaped, or planoconvex, and often with a sharp ventral ridge; the coronoid process is finger-like and laterally hooked. The angular process is thick and separated from the condyle by a deep groove. Lastly, balaenopterid mandibles are often laterally bowed, like cetotheriids, but then medially bowed near the condyle, resulting in a sinuous shape.

The mandible of the gray whale, Eschrichtius robustus, with cross sections in approximate location relative to the above diagram. Modified from Demere (1986).

The mandible of gray whales, on the other hand, is quite distinctive. The mandible is nearly straight, lacking the extreme bowing of balaenopterids, and absolutely lacking the sinuous profile. Most mandibles would be 1.5-3 meters long. The mandible is dorsoventrally deep with a flattened shape, and the mandible can also be somewhat dorsally arched. The posterior end is the most diagnostic, however. Like balaenids, the coronoid process is highly reduced to a small tubercle, and the mandibular condyle is very large and elevated - elevated far above the dorsal edge of the mandible. However, unlike a balaenid, the condyle is narrow, a bit more like a balaenopterid.

With these features in mind, it's easy to identify mandibles, often even when represented by partial specimens. This was the case with the mandible fragment reported by Tsai et al. xxx from Belgium. In my case, no specimen yet collected from the Purisima Formation clearly represents an eschrichtiid - though I would expect them to be there. Especially the unnamed species represented in the San Diego Formation - the Purisima shares many other marine mammal species, including Valenictus chulavistensis, Callorhinus gilmorei, Parapontoporia sternbergi, Semirostrum ceruttii, and others.

The partially poached mandible in the cliff. An inexperienced collector has removed much of the anterior 2/3 of the mandible but left the posterior end, and the tip in place.

But what about specimens I've seen out in the field? Here is a mandible that I saw poking out of the cliff when I was doing some fieldwork under a California State Parks permit back in about 2010 or so. While I was away at college at MSU Bozeman, I got an email from one of the rangers, alerting me to this specimen. Someone had dug out the middle part of the mandible. That was unfortunate - I had thought about excavating it, but it would have been a pain, as its location in the intertidal zone at the base of a cliff would require it to be collected in several segments to be reassembled rather than as a complete plaster jacket. Given the damage to the specimen, its risky location, and my impending move to New Zealand, I decided against collecting the specimen. But, maybe the specimen can still be informative?

The anterior end of the mandible, left in the cliff. It's difficult to see but the anterior end is dorsoventrally deep and transversely narrow - more like a gray whale (Eschrichtiidae) than a rorqual (Balaenopteridae).

The posterior end of the poached mandible in lateral view. The coronoid process is hidden, but the mandibular condyle looks like it is quite elevated - perhaps above the level of the coronoid, and certainly much higher than the base of the coronoid.

And an oblique view of the posterior end of the mandible. Here you can see that the mandible was quite straight - the excavated trough corresponding to the inner edge of the mandible curves only about 10-15 degrees or so.

A few features tell us very quickly what this mandible does NOT belong to. First, it has a relatively small mandibular condyle, and a slightly sinuous (medially bent) posterior part, and, evidently, at least a low coronoid process that is nearly raised to the level of the condyle - all of these indicate that it is not from a right whale (Balaenidae). Second, it is much too large to be Herpetocetus - the only Pliocene cetotheriid in the North Pacific - and the mandibular condyle is rounded, not set off to the side and flattened. The angular process is rounded, not like the posteriorly directed shelf seen in Herpetocetus; Herpetocetus also doesn't have a 'reflexed' posterior end. The reflexed or sinusoidal outline of the posterior end indicates that the mandible is a balaenopteroid - either a gray whale in the Eschrichtiidae, or a balaenopterid. The mandibular condyle seems quite high - much higher than what appears to be the base of the coronoid. The mandible is not strongly arched, unlike many, if not most, extinct balaenopterids. The anterior end seems quite tall and narrow. All of these features suggest that this could belong to an early gray whale with some balaenopterid-like features. However, we don't know what the middle of the mandible looks like, and the posterior end and the coronoid, at the time of my photos, were still embedded in rock. So, it is entirely possible that these features might be misinterpreted owing to an 'optical illusion' - or what I call an 'erosional mirage'. Sometimes, the way a specimen erodes out makes it look like something else, something more exotic. To borrow a phrase from medicine, "when you hear hoof beats, look for horses, not zebras." In field paleontology, we're always trying to find "zebras", and an odd plane of erosion in combination with wishful thinking has led many astray before (including myself!). In this case, gray whales are the "zebra" and balaenopterids are the "horses" (if it wasn't obvious). One important caveat here: this is by no means a fossil example of the modern gray whale Eschrichtius. This is admittedly one of a few early eschrichtiids with balaenopterid like features. We should expect to find the "San Diego gray whale" in the Purisima Formation at some point, given that they are the same age and baleen whales tend to have very large areas of distribution. Unfortunately, we'll never know - the specimen completely eroded away between the time that I left for my Ph.D. in New Zealand and before I applied for a new permit in 2015. However, this is in part OK, because some other enticing discoveries at other Purisima Formation localities have been made - and once they are prepared, I am certain will demonstrate the presence of gray whales in the same unit.

On a final note: if the person who dug this out of the cliff happens to read this, please get in touch with me. I'd love to see the specimen if it still exists.

More on gray whales later this year! Stay tuned...

The fossil record and evolution of Kelp and Kelp forest ecosystems

2026-06-02T12:07:33.732-07:00

A kelp forest consisting mostly of giant kelp (Macrocystis pyrifera) at La Jolla, photographed by the author.

Introduction to the Laminariales

Kelps are large brown algae that grow nearly worldwide in temperate and cold temperate waters. Kelps are the world's largest types of algae; most are all members of the Brown Algae (Phaeophyceae). While most famous for the largest species that produce kelp forests, most species of kelp are quite small, with many "medium sized" species growing to only a few meters, and even more numerous species growing to lengths less than a meter. The most important thing that defines kelp is not necessarily its size, or its structure, but the way it grows: it grows from the base - like grass blades - rather than at the tips, like trees do on land. Later on I'll discuss why this adaptation is considered to be a key innovation and the foundation of some modern marine ecosystems. Most kelp species are within the Laminariales, including the most famous forms such as giant kelp (Macrocystis) and bull kelp (Nereocystis) - but there is a separate group of brown algae, the Fucales, that include some forms that are also called kelp, such as the southern bull kelp (Durvillaea spp.). I'll be focusing on the Laminariales, with occasional mentions of Fucales.

The kelp forest tank at the Monterey Bay aquarium, featuring giant kelp (Macrocystis pyrifera), leopard sharks (Triakis semifasciata), sea chubs (Kyphosus), rockfish (Sebastes), senoritas (Halichoeres), and others. Photo by the author.

Kelp Phylogeny

Kelps, or the order/clade Laminariales, are a group within the Brown Algae or the Phaeophyceae; there are about 2,000 species of brown algae, and species of kelp are quite limited in diversity - about 120 species in 30 genera. The earliest diverging species are quite small and filament-like (Chorda spp.). Most of the more obviously kelp-looking species with large blades that diverge after these filamentous forms have large, single blades that might branch somewhat - the genera Alaria, Pleurophycus, and Laminaria (the kelp that gives the group its name). Also in this group is the Western North Pacific Undaria, known in Japan as Wakame - edible seaweed. Closely related to Laminaria are the southern kelps in the genus Lessonia, which looks a bit like giant kelp without bladders or a long stipe. Feather boa kelp (Egregia menziesii) diverges next - which forms our shallow water kelp forests here in California, and can be surprisingly long, up to 15 meters.

Molecular phylogenetic tree of kelps (Laminariales) from Starko et al. (2019).

The next diverging clade is the genus Ecklonia - these kelps look similar to Lessonia and Laminaria and consist of a short stipe and a bunch of long blades, forming dense but relatively shallow kelp forests only a couple of meters tall; these kelps live in Japan, the eastern Atlantic, and throughout the southern Ocean. There are loads of videos of giant cuttlefish filmed along the south coast of Australia - above 'forests' of Ecklonia.

The next group is perhaps the most important, worldwide, and also because of the regional focus of this blog - a tight clade formed by the sea palm (Postelsia palmaefloris), bull kelp (Nereocystis luetkeana), elk kelp (Pelagophycus porra), and of course, giant kelp (Macrocystis pyrifera). With the exception of sea palms (which colonize the most highly wave-battered rocks in the intertidal zones and are true gluttons for punishment), these kelps form the backbone of North Pacific kelp forests, along with feather boa kelp (Egregia), and can grow to incredible heights (45 meters in Macrocystis; 35 meters in Nereocystis; 30 meters in Pelagophycus). For simplicity's sake, I'll refer to these species as the "California kelp clade" since most of these species overlap in California.

After these giants is the most recently evolved clade, a closely related grouping of two dozen species mostly belonging to the genus Saccharina (though this might be taxonomically split up), mostly in the western North Pacific and Aleutians. As the name suggests, these are edible; S. japonicus is known in Japan as kombu. While economically important, these kelps do not get very large (1-2 meters). Here along the Pacific coast we have Saccharina dentigera.

Giant kelp (Macrocystis pyrifera) backlit by the sun, just off La Jolla, California. For this shot I had to swim down about 20 feet and aim upwards. Photo by the author.

My best macro shot of giant kelp (Macrocystis pyrifera) showing the apicalmost pneumatocysts and fronds. Laguna Beach, California. Photo by the author.

The North Pacific kelps - Nereocystis, Macrocystis, Pelagophycus, and Postelsia

The four kelp species native to the eastern North Pacific are the world's most famous and immediately distinctive kelp species. Giant kelp, Macrocystis pyrifera, is first among these - though it has colonized the southern Ocean as well (I was surprised to see it in New Zealand, and just fully expected it to be a different species when I first saw it). This species is a popular target for underwater photographers, myself included, and I have spent a fair amount of time snorkeling amongst the giant kelp forests around La Jolla here in southern California. This species has many individual small gas-filled bladders (pneumatocysts) that suspend the entire stalk in the water column, and can grow to heights of 45-60 meters (150-200 feet); it tends to live in water of the same depth, reaching the surface. I've seen small giant kelp growing in tidepools, and small stands of relatively short giant kelp in water about 5-7 meters deep. This species inhabits waters below 21C/70F, and starts to get pretty ragged when the water here in San Diego exceeds 70F. As a result, along the Pacific coast, it doesn't live much further south than here, rarely growing south of Ensenada in Baja California (though there are some records from the Vizcaino Peninsula midway down the peninsula). This species has dispersed to the southern hemisphere, and lives extensively along the temperate Pacific coastline of South America from southern Peru to Tierra del Fuego, South Africa, southestern Australia (Victoria, South Australia, and Tasmania), New Zealand, and many islands throughout the Southern Ocean, including some off the Antarctic Peninsula. In the north, it doesn't extend any further north or west than southern Alaska; on Inaturalist, there are a couple of records from Kodiak Island, and that's it.

A dense forest and canopy of bull kelp (Nereocystis luetkeana). Just off northern Vancouver Island. Photo by Neil McDaniel via Inaturalist.

A closeup of the pneumatocysts and fronds of bull kelp (Nereocystis luetkeana). Just off northern Vancouver Island. Photo by Neil McDaniel via Inaturalist.

Bull kelp, Nereocystis luetkeana, is perhaps the second most recognizable kelp species, and is restricted to the North Pacific. It has a somewhat more contracted range, from southern California through the Aleutians and possibly as far west as the Commander Islands (though these are beach wrack records on Inaturalist and could have floated there from hundreds of miles away). Like giant kelp, bull kelp attaches chiefly to rocky bottoms but has a rather massive cylindrical stipe and a single gigantic pneumatocyst that in fully grown individuals is about the size of a softball. A number of fronds attach directly to this pneumatocyst. Bull kelp rarely forms dense canopies in central and southern California, and dense accumulations of this species are more typical in the Pacific Northwest. Not quite as large as giant kelp, this species can grow to about 36 meters (118 feet) and tends to live in waters up to that depth. I can only imagine that one common name of bull kelp, bullwhip kelp, came about owing to the narrowly tapering stipe; I can't count the number of people I've seen whipping this kelp at each other (and being surprised by how much it hurts). I learned my lesson when I was a kid (the whipper usually gets hurt more than the whip-ee). In 2010, I got to see fellow paleontologist Denver Fowler learn the same lesson!

A stunning shot of a relatively large elk kelp (Pelagophycus porra) with five fronds per side. Just off Ocean Beach, San Diego, California. Photo by Melissa Foo via Inaturalist.com.

A loose stand of elk kelp (Pelagophyca porra) deep down in the photic zone. Photo by Brett Seymour via National Park Service.

Elk kelp (Pelagophycus porra) is an unusual species with a restricted range only in southern California and northern Baja California, from Point Conception near Santa Barbara down to about the middle of Baja California. This species looks like a cross between giant kelp and elk kelp. Like the latter, it has a single gigantic pneumatocyst about the size of a softball or somewhat larger, but it has a few branching fronds that branch off the pneumatocyst in a pectinage pattern like giant kelp; head-on, the pneumatocyst looks like it has antlers. And, indeed, when washed up on shore with the fronds chewed off, it really looks like you've found a flexible decaying antler. This species inhabits deeper waters, as shallow as 20 meters deep (66 feet) down to 90 meters (300 feet) and to a length/height of 7-27 meters (~20-90 feet). Elk kelp forests are deep, well below the low tide line, and less densely forested than giant and bull kelp forests. It mostly lives in waters cooler than 60F (15C). Unlike giant and bull kelp, elk kelp frequently attaches its holdfast to soft sand and gravel or shelly bottoms - a critical adaptation for it being such a deep species given the less frequent presence of rocky substrates further from shore.

A cluster of sea palms, Postelsia palmaefloris, in between waves at Pigeon Point along the southern San Mateo County coastline in California. Despite being quite small, Postelsia is the sister taxon of bull kelp, Nereocystis luetkeana. I took this photo the safe way: from the top of a rocky headland through a telephoto lens. Pigeon Point, California. Photo by the author.

Stalks of sea palms (Postelsia palmaefloris) ripped by the wave action they have adapted to living within.

Lastly, the sea palm, Postelsia palmaefloris, is a bit of a dwarf in this group. It can form dense little forests, but it only grows to about a 50-70 cm high. It also grows completely within the intertidal zone - and specifically, the middle and upper intertidal zones. It competes for space with California mussels (Mytilus californicus) and often rapidly colonizes surfaces where mussels might get blasted off by powerful winter waves. They have a stiff stipe and short fronds only up to 20-30 cm in length - it doesn't have pneumatocysts. You rarely see a single sea palm - they usually grown in small stands (not unlike land palms). I've never seen a live sea palm close up, for one major reason: I'd have to have a suicide wish to get that close to them. Most of the sea palms along the Northern California coast are in really dangerous settings. Unless you can get out onto some rocky outcroppings studded with mussels that get absolutely blasted by waves at a minus tide, you won't get close to them. I have seen them the safe way: with a telephoto lens from fifty meters away, or washed up on a beach. Apparently, sea palms live for about a year, and the 'stands' are ephemeral - once the sea palms die naturally or are wrenched off the rocks by merciless waves, the substrate can be quickly overrun by mussels. What is quite curious is that this species is the sister taxon to bull kelp, and is fully nested within the 'California kelp clade' formed by bull, elk, and giant kelp - indicating that the ancestor to sea palms likely was a canopy-forming kelp with pneumatocysts that became an intertidal dwarf kelp and lost its pneumatocysts.

The apex of a giant kelp (Macrocystis pyrifera) frond photographed at night and backlit - one of my nicest kelp photos. You can clearly see the turnip shaped pneumatocysts that keep this species of kelp aloft off the sea floor. San Diego, California. Photo by the author.

The single pneumatocyst of a rather young bull kelp, Nereocystis lutkeana. If this had been loose and not attached to a rock, it would have been a lovely specimen to collect and try to make a pressing of. Photo by the author.

Adaptations of Kelp

There are three major adaptations of kelp that have resulted in rapid growth and enormous size. One of the major adaptations of kelp is that growth occurs at the meristem (junction between the stipe and 'blades') and, in the larger forms, the base of the stipe (stem) rather than at the distal ('upper') parts of the kelp. This is an adaptation against extreme grazing, as the canopy can be consumed at a rapid rate but the 'conveyor belt' of kelp growth keeps bringing new kelp fronds to the surface. If the distal fronds get eaten first, that would greatly decrease growth if that's the part of the alga that is growing. This is much the same way that grass and bamboo (a giant type of grass) grow, and a bit different from how trees and many flowering plants grow. Giant and bull kelp can grow at a rate of a half meter per day (slower than bamboo on land at up to a meter or so per day, but still objectively rapid). The second is that many large kelps - ones that are longer than a few meters - have some kind of gas-filled bladder, known as a pneumatocyst. In elk kelp (Pelagophycus) and bull kelp (Nereocystis), there is one huge bladder; in giant kelp (Macrocystis) and feather boa kelp (Egregia), there are numerous small pneumatocysts. As you might predict from convergent evolution, pneumatocysts in kelp are not all filled with the same type of gas - some are filled with a mixture of oxygen (O2), carbon dioxide (CO2), nitrogen (N2), and even carbon monoxide (CO). Oxygen is the most common. The ratio of gas chemistry by volume does not seem to change with growth, at least in bull kelp where it has been studied. Instead of pneumatocysts, the Fucalean southern bull kelp (Durvillaea) has a honeycomb-like internal structure with internal gas-filled spaces that provide buoyancy.

The rather small and simple holdfasts of feather boa kelp (Egregia menziesii), photographed in the lower intertidal during a minus tide at the Great Tidepool in Pacific Grove, California. Photo by the author.

Some more feather boa kelp (Egregia menziesii) holdfasts emerging from shifting sands. La Jolla, California. Photo by the author.

Most species of kelp (and algae in general) attach directly to rocks. Unlike plants, these are not roots - kelp already lives in the water, so uptake of water and nutrients is done directly from the water column. As a result, the attachment structure is purely mechanical and called a holdfast. The stipe expands and branches into a series of short, stout, tangled branches that extend outwards and contact the rock. Sometimes this can be rather short and stocky, as in the sea palms (Postelsia), and in some early diverging kelps, is even just a simple non-branching or 'discoidal' holdfast (Aureophycus). Some studies (Kawai et al. 2013) even proposed that this discoidal holdfast is the primitive condition for kelps. In many of the larger species, however, it can be a surprisingly large tangle of branches; in cross-section, it will look like a series of nested cones - each set of branches extends radially off of the stipe and slopes downwards toward the rock. As the kelp grows, so does the holdfast - another outer layer of holdfast branches are grown, one at a time. Large holdfasts can attain nearly a meter in size in giant kelp, though most holdfasts you might come across on the beach will range about 10-30 cm in diameter. Kelp holdfasts have even recently been found as fossils (see below).

A macro shot of the stipe of feather boa kelp (Egregia menziesii). There are two pneumatocysts in this shot but they're behind fronds at the lower left and right. La Jolla, California; photo by the author.

As in other algae (and in plants), kelps undergo a sporophyte (spore-bearing) and gametophyte (gamete-bearing) phase. The sporophyte is what we usually see: this is the large form anchored to the seafloor. It produces spores (which are diploid - possessing two copies of each chromosome), which mature into (still microscopic) male and female gametophytes (which are haploid, or possessing one single copy of each chromosome). Once the male and female gametophytes contact and 'fuse', a new sporophyte starts to grow and settles somewhere.

A giant kelp (Macrocystis pyrifera) sporophyll I found while snorkeling near La Jolla, California. Photo by the author. This individual threw me through a loop because it really, really looks like Lessonia from the southern hemisphere!

Giant kelp (Macrocystis pyrifera) is further notable for two reasons. First, it produces spore-rich growths called sporophylls near the base of the stipe. I recently came across a giant kelp sporophyll but had no idea what kind of kelp it was - it had no bladders (pneumatocysts) and had a short stipe, and didn't match anything. Additionally, the main stipe had evidently been removed or lost at some point. So - some kelps produce a separate spore-bearing growth that looks a bit different from the mature sporophyte. Second, and perhaps more fundamentally, the extensive pneumatocysts in this species have permitted it to disperse to the southern hemisphere - it inhabits New Zealand, southern South America, Tasmania, and many of the islands of the southern ocean in the vicinity of New Zealand, Australia, and South America. Initially named as different species, molecular work has recently determined that all of these are the same species with a North Pacific origin, and drift kelp probably dispersed southward in the tropical eastern Pacific during the late Pleistocene (when, presumably, this species would have been growing even closer to the equator). Cooler waters would have permitted the drift kelp to survive the journey (kelp doesn't tolerate warm water very well - an ominous note for today's kelp forests) and spread spores into the southern ocean. The lack of giant kelp in South Africa is puzzling, given the west to east direction of the circumpolar current.

Close up shot of the fronds of southern sea palm, Eisenia arborea. La Jolla, California. Photo by the author.

Lastly, many kelps have phenolic compounds in their tissues that are thought to be a sort of chemical defense against herbivores, much like the chemical defenses in many modern plants. Some of these phenolic compounds, polyphloroglucinols, are present (and quite abundant by volume) in most if not all brown algae, and experimentally have been shown to deter feeding by herbivorous gastropods and echinoids. In the North Pacific, some phenolic rich kelp (Agarum) is grazed at a much lower rate than phenolic poor kelp (Laminaria). Curiously, southern hemisphere species of kelp have dramatically higher levels of phenolic compounds than northern hemisphere species, leading at least one major study to propose that sea otter predation on marine invertebrate herbivores (e.g. sea urchins) decreased the adaptive necessity for kelp species in the North Pacific to evolve chemical defenses (Estes and Steinberg 1988).

Large fronds of southern bull kelp (Durvillaea antarctica) attached to Miocene age basalts, Tairoa Head, Otago Peninsula, New Zealand. Photo by the author.

Southern Bull Kelp - Durvillaea

Southern bull kelp (Durvillaea spp.) is not a true kelp in the order Laminariales but is a clade within the Fucales - a closely related group of brown algae; Durvillaea is actually somewhat closely related to Sargassum - that floating yellowy algae we were used to seeing wash up on east coast beaches during the summer. Southern bull kelp includes about eight species in the genus Durvillaea, and in New Zealand, we saw Durvillaea antarctica. Southern bull kelp doesn't float in the same way - the fronds themselves are filled with air and have an internal honeycomb texture, so the fronds float. Each frond is attached to a short and rather robust stalk, many of which can share the same holdfast; the fronds themselves are long and spindly or can be quite wide, but diverge off of a palmate expansion, a bit like Laminaria. It grows to a length of 10 meters, and only grows on rocks that take quite a beating from the waves - and, as a result, tends to only grow shallowly with the holdfasts in the intertidal zone (most species, including D. antarctica) or just below it (D. willana lives at a maximum depth of 6 meters). So, while southern bull kelp is called kelp because it is quite large and floats, it doesn't really form kelp forests as much as it does form halos around rocks - in terms of its attachment and growth, it has far more in common with sea palms (Postelsia spp.) in the North Pacific, which are restricted to the intertidal zone on the most violently wavy coastlines.

Southern bull kelp, Durvillaea antarctica, at Cannibal Bay in the Catlins, New Zealand. Here is Sarah for scale (5'4") to show the absurd scale of this algae. At low tide like this it rather looks like lasagna. Photo by the author.

More southern bull kelp, Durvillaea antarctica, at Tairoa Head, Otago Peninsula, New Zealand. Here it rather resembles angel hair pasta instead.

We first saw this species during our first visit to St Clair beach on the south side of Dunedin, and were amazed with the size of the fronds - far larger than anything from California - but also the colossal stench. I'm used to stinky wracks of kelp, since I was a kid visiting Moss Beach in the early 90s. Beach wrack consisting of fresh kelp is odorous enough, but after a few weeks of decomposition this black sludge begins to form in the middle - and it is putrid for sure. But the smell of even slightly decayed Durvillaea is something else. Regardless, Durvillaea is quite beautiful and its tendency to float means that the individual fronds can spread out like the spiky bits of a palm frond. At high tide, the thicker bits of the algae float in a tangled mass that can only be described as resembling giant green lasagna.

Kelp forest dominated by giant kelp (Macrocystis pyrifera) just off La Jolla, California. Photo by the author.

Kelp Forests

In many of the temperate and cold temperate parts of the world, there are extensive kelp forests where kelps grow quite densely, and with different types growing together. Kelp forests make up less than 1/1000 of the surface area of the earth - yet are responsible for just about 1% of all productivity on the planet, especially along coasts with extreme upwelling.

The Pacific coast of North America - especially California - hosts what is arguably the world's most famous kelp forests, and the most complex. Giant kelp (Macrocystis) and Bull kelp (Nereocystis) form a canopy, and smaller kelps such as Laminaria (no common name), feather boa kelp (Egregia), southern sea palms (Eisenia), stalked kelp (Pterygophora), and many others grow closer to the seafloor. Below these can be found red algae and many sessile marine invertebrates.

A kelp isopod (Pentidotea wosnesenskii), one of many marine invertebrates that have adapted to live on or around kelp. La Jolla, California. Photo by the author.

Kelp species that grow sufficiently long may attach to rocky substrate, and be suspended vertically in the water column through buoyant gas filled bladders (pneumatocysts). The major examples of these are giant kelp (Macrocystis), bull kelp (Nereocystis), and in deeper offshore waters of southern California, elk kelp (Pelagophycus). Pneumatocysts permit the fronds to float higher in the water column, and thus better able to photosynthesize; this is presumably an adaptation for being able to colonize deeper settings that smaller kelp species cannot.

Kelp forests are further one of the highest productivity marine environments out there - chiefly by their rapid growth, and the near constant delivery of dead kelp bits - drift kelp - into shallow marine settings. Visit any beach in California, especially in summer and fall, and you'll probably find bits of kelp - either small fragments, or entire kelp stalks (e.g. after storms) - washed up on the beach. I often come across floating kelp strands while snorkeling (and use the opportunity to look for a couple of kelp forest dwelling sea slugs you can't find during tidepooling... but never seem to spot them). These bits of drift kelp feed herbivorous invertebrates - in fact, most purple urchins live in small, spherical borings and never leave, and catch little bits of drift kelp with their tube feet and pull it into the burrow. Drift kelp in turns feeds and causes population booms of microorganisms that filtered out of the water column by filtering invertebrates - and even microscopic bits of kelp detritus can form the primary food of some filtering invertebrates like mussels and barnacles. For these reasons, driven by a few growth adaptations, kelp forests are one of, if not the most productive marine environments on the planet. Though kelp can grow quite rapidly, most species do not live very long. Giant kelp lives for about three years, and bull kelp generally lives for one year - though some individuals live a second year. Young bull kelp and giant kelp can be found in winter, and they become giants by late spring; large adult kelp washes up in abundance during the fall.

A Norris' top snail (Norrisia norrisii) - this gastropod lives subtidally and often grazes algal and diatomaceous films off of kelp. La Jolla, California. Photo by the author.

Some really chewed up giant kelp (Macrocystis pyrifera). I'm not sure if these snails, gilded tegulas (Tegula aureocincta) are the root of this herbivory; this was photographed during a heat wave that triggered accelerated grazing (and decomposition, according to some) of the kelp near the surface. Indeed, it was about 73-74F when I shot this - no wetsuit required! La Jolla, California. Photo by the author.

In certain areas, kelp can become overgrazed by sea urchins - leading to rocky bottoms overcolonized by dense aggregations of purple urchins (Strongylocentrotus purpuratus). These are called urchin barrens. As described below, sea urchins typically live in small spherical borings and "catch" bits of drift kelp and other algae and feed on those. When this food source becomes too scarce, they leave their borings, and start to graze directly on live algae - rapidly consuming kelp and destroying the kelp forest. Sea otters and sea stars keep urchins in check today - and areas where sea otters have re-colonized since their near extinction in the late 19th centory have seen the return of kelp forests. Today, urchin barrens are common north of Santa Cruz, California, through Oregon, and Washington - few kelp forests exist in these regions. Additionally, even areas where sea otters are common, including around Monterey, have had worrying declines in kelp forests.

A rare kelp clingfish (Rimicola muscarum), one of two that I have been very privileged to find while tidepooling. Clingfish have a little suction cup underneath their head formed by modified pelvic fins. La Jolla, California. Photo by the author.

More grazing on kelp - southern sea palm (Eisenia arborea), with a large gilded tegula snail (Tegula aureocincta) and some limpets (Lottia) and their corresponding traces. La Jolla, California. Photo by the author.

Simplified diagram of the keystone species hypothesis for sea otters. Image Credit: Pearson Education.

Sea Otters and Kelp Forest Ecosystems

The single most famous marine mammal on the California coast today is the sea otter, Enhydra lutris. It's the smallest marine mammal on earth, and the largest member of the weasel family, Mustelidae. Prior to the fur trade, this species had a nearly continuous distribution throughout ice-free coastlines of the North Pacific, from northern Japan to the Commander Islands, east through the Aleutians and the Alaskan panhandle, south through British Columbia, Washington, Oregon, California, and northern Baja California. Sea otters are generalist carnivores that feed on a variety of vertebrates and invertebrates - fish, octopus, clams, scallops, gastropods, crustaceans, and echinoids. Their predation of sea urchins is the most well known of these, and they can occasionally eat so many purple urchins that the pigment echinochrome can actually stain their teeth and bones a pale purple color. Not all sea otters eat urchins, and in fact, many do not - sea otters are generalists, as a species, but as individuals, it turns out that they are specialists. They can be very picky - focusing on just a couple of prey species. In fields of urchin barrens populated by malnourished 'zombie urchins' surviving on a fraction of their soft tissue body mass - sea otters often won't even touch these urchins when given the opportunity. One of my favorite anecdotes is that during feeding experiments with Alaskan sea otters in the 50s/60s, it turns out that whenever two food choices were given, and one of those choices was octopus, sea otters picked the octopus every single time.

Differences in urchin (Strongylocentrotus) populations between the sea otter rich "Rat Islands" like Amchitka Island (left) and the otter free "Near Islands" like Shemya Island (right). Note how much larger sea urchins get in otter free environments, and how much more urchin biomass there is (gray histogram). From Estes and Palmisano (1974).

Studies of islands in the Aleutians with and without sea otter populations in the 1970s resulted in a dramatic observation (Estes and Palmisano 1974). Surveys for sea urchins (white and green urchins, both in Strongylocentrotus, same genus as our purple urchin) on two islands - Shemya Island (part of the 'Near Islands'), without otters, and Amchitka Island (part of the 'Rat Islands'), with the most dense otter population in this part of the Aleutians - resulted in vast differences in urchin populations. Sea urchins were numerically more abundant on Shemya Island and attained much larger sizes - with a juvenile peak of ~15 mm test (shell) diameter (I imagine the prior year's spawn), and an 'adult' peak of about 65 mm test diameter. Critically, the abundance of larger individuals meant that the 'biomass' of urchins was considerably higher in the waters around Amchitka Island. Around Shemya Island, there were no urchins found over 35mm test diameter, and the peak was at about 25 mm diameter, and the biomass in general is a fraction of that at Amchitka Island. At Shemya Island and others in the "Near Islands" where sea otters have been extirpated, kelps are quite reduced, and wide expanses of rock are covered by dense accumulations of mussels and barnacles (not too unlike some of the intertidal zone in select locations on the California coast). Here, chitons and urchins graze away much of the algae. In the "Rat Islands" with abundant sea otters, there are instead dense kelp beds and other algae, and sessile invertebrates like mussels and barnacles are less than 1% of that seen in the Near Islands. Further, in the Near Islands, there are virtually zero large algae species living subtidally - and instead are surrounded by 'urchin barrens'.

A sea otter snacking on a ?Pismo clam in Morro Bay, California. Photo by the author.

These authors proposed that sea otters are a keystone species, and that their predation of sea urchins in the Aleutians keeps their biomass and body size to a minimum, essentially suppressing their ability to wipe out kelp forests through overgrazing. It is widely hoped that if sea otter populations expand, either through reintroduction or natural expansion, that sea otters may help bring back kelp forests to the coasts of Oregon, southern Washington, and northern California. Reintroduction has not always gone well, however. In the 1960s, a bunch of otters were removed from Adak Island by US Fish and Wildlife prior to nuclear weapons testing. These otters were airlifted to coastal Oregon - many died in transit. Most of the 93 otters disappeared within two years of being reintroduced - and it's unclear why; perhaps they spread out too far and few between and were unable to form a viable breeding population. In the late 1980s, 140 otters were set loose around San Nicholas Island, one of the most remote of the Channel Islands off southern California. Within a year, many of the individual relocated otters had swum back to the California coast! By 2005, only 30 otters remained. However, there is still a similar sized population today. Otter relocations in southern Alaska and Washington are more successful - 400 of the Aleutian otters were relocated to southeast Alaska, and now there's a population of over 20,000. In 1970, about 60 otters were relocated to Washington, and there are now nearly 3,000 otters there. The southern population in California increased year over year until about a decade ago, where it peaked at about 3300 otters; it's been hovering around that number ever since, suggesting that the California population is at carrying capacity. Further, otters are only very rarely spotted north of Santa Cruz, California - and have not seemed to make the jump past the Bay Area to the more uninhabited Marin, Sonoma, and Mendocino coasts. I strongly feel that if enough otters make it up there, they'll really go hog wild. But, that hasn't happened yet - begging the question: will sea otter populations expand in time to save kelp forests, or will continued losses of kelp forests slowly lower the carrying capacity for sea otters? I'm no ecologist and have an admittedly shallow understanding of these issues, but these questions are the sort to keep me awake at night.

The Origin of Kelp and Kelp Forests

The timing of divergence of modern kelp lineages has been analyzed through molecular clock dating - this is a method where mutation rates for particular genes are assumed to be constant through time. Under this assumption, the timing - in thousands, hundreds of thousands, or millions of years - can be calculated for individual branching events on a cladogram (family tree). In one recent 2019 study (Starko), the reconstructed radiation of the Laminariales falls in the Paleogene period - likely during the Oligocene epoch, but with considerable error bars - as early as the middle Eocene (~48 Mya) and possibly as late as the early Miocene (~21 Mya) but with a mean estimate of early Oligocene (32 Mya). This study used the Miocene fossil kelp Julescraneia grandicornis from the Monterey Formation to calibrate the molecular clock - a built in 'correction' that pulls part of the tree to a particular point in time. Additionally, this study found that there was an increase in speciation rate during the late Oligocene through early Miocene, from about 30-20 Mya.

Biogeographic analysis of kelp species: each color corresponds to the likely center of origin calculated for each 'node' (branch splitting point) on the tree. Red = southern ocean; yellow = Atlantic and Arctic; light blue = temperate eastern Pacific coast; dark blue = Alaska and the Aleutians; green = Kamchatka and the sea of Okhotsk; and light green = Japan, China, Korea, and the Yellow Sea. Note that many species have a western OR eastern Pacific distribution (e.g. many are Alaska + the temperate eastern Pacific). Most species of Saccharina are in the western North Pacific, the gigantic 'true' kelp forms (giant, bull, elk, and their red-headed stepchild, the sea palm) are all from the eastern North Pacific); Lessonia is entirely in the southern hemisphere, and a couple species of Laminaria are entirely in the Atlantic. The blue on the pie charts on the stem of the tree indicates that the eastern North Pacific is the center of origin for all kelp lineages.

The geographic center of origin for kelp is certainly to be found somewhere in the North Pacific. Earlier studies suggested an origin in the western North Pacific (e.g. Japan, Kamchatka). However, a recent study (Starko et al. 2019) found that the Laminariales probably originated in the eastern North Pacific, with most lineages found outside this region being 'exported' to other regions (e.g. western North Pacific, southern Ocean, North Atlantic) during the Miocene and Pliocene epochs. The diversification of the western North Pacific "Saccarhina" clade seems to have happened quite rapidly, mostly since the late Miocene. The 'California kelp' clade of kelps including sea palms (Postelsia), giant kelp (Macrocystis), bull kelp (Nereocystis), and elk kelp (Pelagophycus) have an origination in the late Miocene - about 13 Mya - with all four lineages being fully differentiated by the latest Miocene, ~6-7 Mya (though it is worth noting that more recent dates for the microfossil ages for the fossils used for this molecular clock date may indicate that the clade diversified even more recently than that, around 8 Ma).

A school of kelp bass (Paralabrax clathratus) underneath fronds of giant kelp (Macrocystis pyrifera), just off La Jolla. Photo by the author.

Kelp forests, on the other hand, likely have a slightly different history. Adaptations for upright growth - chiefly, the development of stiff stipes, pneumatocysts, and branching - have evolved several times, but apparently quite recently. It seems most likely that until the last few million years, perhaps the Pliocene - kelp forests consisted of relatively "short" species only a few meters in length, similar to the kelp forests of the southern Australian coastline. Perhaps tall canopy kelps did not evolve until the last few million years - and species of limpets that feed only on kelp stipes (with a distinctive aperture shape, and a narrow shell that conforms to the width of the stipe) only appear in marine rocks that are a maximum of 3 Mya in age (see below).

Another recent study, summarized below, reports relatively small kelp holdfasts from the early Oligocene Makah Formation of the Olympic Peninsula in Washington state. These holdfasts consist of a complex structure of the 'roots' - haptera - and are identifiable to the Laminariales or true kelps. These holdfasts are similar in complexity to giant kelp (Macrocystis) and are very similar to bull kelp (Nereocystis). Given that 1) these holdfasts pre-date the fossil record of the canopy forming kelps like Julescraneia (see below) by over 20 million years, 2) they likely represent a kelp form with a soft rather than stiff stipe, and 3) owing to their relatively small size, it is likely that these represent some other clade than those in the 'California kelp clade'. Further, it seems likely that these holdfasts, if they did not possess a stiff stipe, were not canopy formers. I imagine a South Australia kelp forest situation with Ecklonia-like kelp growing a few meters above the seafloor, or perhaps if these kelps had pnmeumatocysts, something similar to the shallow marine feather boa kelp 'forest' that tends to occur on the California coast inshore of the giant kelp forests.

The holotype slabs of Julescraniea grandicornis from the upper Miocene Monterey Formation of California, from Dawson Parker and Dawson (1996).

Branching pattern of frond 'antlers' in elk kelp (Pelagophycus), bull kelp (Nereocystis), and the extinct intermediate form Julescraneia grandicornis. From Parker and Dawson (1966).

The fossil record of kelp

Kelp Fronds: There is really only one known 'body' fossil of kelp - and that is Julescraneia grandicornis from the upper Miocene Monterey Formation of Los Angeles County. This fossil was described by Bruce Parker and E. Yale Dawson in 1966 from LACM collections (later transferred to UCMP collections at Berkeley). It's large, and shares features with both Nereocystis (bull kelp) and Pelagophycus (elk kelp). The specimen preserves a large pneumatocyst likely 16 cm in diameter when alive, but crushed and flattened so it is preserved now as 22 cm. The basal 'antlers' leading to the fronds are preserved, but none of the fronds themselves, and it's likely to be a piece of pretty rotten drift kelp that sank to the sea floor. You can actually make out some of the branches terminating. Kelp pneumatocysts can stay inflated for very long periods of time - isolated Macrocystis pneumatocysts with little stubs of the fronds are frequent finds. Given the thick walls of the pneumatocyst in Nereocystis and Pelagophycus, it's a wonder that we have any of these branches at all for Julescraneia. Regardless, the pattern of branching resembles Nereocystis, though the branches are much, much longer, like Pelagophycus. In this regard it has morphological similarities with both of these large-pneumatocyst kelps. Even as far back as 1966, these authors suggested that Julescraneia could potentially have given rise to both elk and bull kelp. Interestingly, despite their large pneumatocyst, these two modern kelps are NOT sister taxa - if you recall from above, bull kelp (Nereocystis) is the sister taxon of sea palms (Postelsia) and elk kelp (Pelagophycus) is sister to giant kelp (Macrocystis). Is the single large pneumatocyst primitive for this clade? Perhaps - three out of four extant species have a single unbranched stipe, and I can easily envision size decrease and loss of a large pneumatocyst resulting in the evolution of sea palms (Postelsia; however, Postelsia has a hollow stipe, which could in theory be homologous to a large, cylindrical pneumatocyst; Starko et al. 2016), and branching of the stipe and addition of pneumatocysts evolving in giant kelp (Macrocystis). In fact, quasi-sympatric speciation into adjacent but slightly different environments likely led to the shrinking of Postelsia as it inhabits much of the same geographic range, but shallower waters along the same rocky shores that Nereocystis occurs just offshore from. Lastly, the age: Julescrania is from LACM locality 1267 in the Monterey Formation on the north side of the Santa Monica mountains in Sherman Oaks, actually quite close to the 405/101 junction just a few miles west of Burbank in Los Angeles County. According to Parker and Dawson, the Monterey Formation here has produced upper Mohnian age diatoms, now corresponding to an age of about 8 Ma.

The fossil algae Postelsiopsis caput-medusae from the Eocene Monte Bolca Lagerstatte of Italy, on display at the Museo dei Fossili di Bolca. Photo by Ghedoghedo via Wikipedia.

Another fossil is a species purported to be closely related to Postelsia palmaefloris from the Monte Bolca lagerstatte of Italy, Postelsiopsis caput-medusae. However, Monte Bolca is Eocene. I don't think it looks particularly close to Postelsia to begin with, and it is now considered to be some other sort of brown algae.

A teeny little holdfast formerly anchoring a feather boa kelp (Egregia menziesii) stalk to the seafloor; the entire kelp was floating around like this. Photographed near La Jolla by the author.

A massive, 50-70cm wide giant kelp (Macrocystis pyrifera) holdfast on the Scripps Pier underwater webcam in October 2025; the kelp had been torn loose from the seafloor and became entangled on the pier pilings, allowing me to get this screenshot. The little spiky things at the upper right are spiny lobsters (Panulirus interruptus).

Holdfasts: There is a slightly larger fossil record of kelp holdfasts, though these were not described until the past couple of years by Kiel et al. (2024). These authors reported no fewer than twelve permineralized holdfasts of some sort of kelp preserved in the Jansen Creek Member of the Makah Formation from the Olympic Peninsula of Washington. Woody debris is not uncommon in this unit, and I've encountered all sorts of bits of wood with a coal-like preservation. These holdfasts greatly resemble those of modern bull and giant kelp, consisting of a tangled mound of branching 'roots' (haptera). In cross-section, the haptera emerge in successive layers and appear to be radially oriented. In other words, each "layer" of haptera is conical, consisting of spoke-like radially oriented haptera, and each new conical layer is larger than the last. These holdfasts are shockingly similar to extant bull kelp (Nereocystis) and giant kelp (Macrocystis) holdfasts, Kiel et al. (2024) interpret these holdfasts as belonging to true kelp in the order Laminariales. At the center of the holdfast, there is no remains of the stipe ("stem") - instead, there is a conical hole from where the stipe was torn away, likely by winter storms (in my opinion). The authors also suggest that, since it is missing like this, the stipe was probably soft, perhaps like feather boa kelp (Egregia) - and that these kelps may not have been 'upright' like canopy kelps (Macrocystis, Pelagophycus, Nereocystis). These holdfasts are not large - ranging up to about 5 cm in diameter, similar in size to the holdfasts of extant feather boa kelp (Egregia). The fossil holdfasts are mostly attached to shells, including barnacles and bivalves including mussels - suggesting shallow water attachment like in the intertidal zone; the modern upper intertidal, for example, is dominated by California mussels and volcano barnacles. Holdfasts also seem to have trapped a number of small fossils including bivalves, gastropods, foraminifera, rocks, and sediment - similar to the microfauna associated with modern kelp holdfasts, which offer some shelter from waves and daily temperature swings.

32 million year old kelp holdfasts from the Makah Formation of Washington - from Kiel et al. (2024).

Summary of geochronologic evidence for the origin of kelp and kelp associated fauna - from Kiel et al. (2024).

The trapping of calcium carbonate mollusk fossils permitted some isotopic analyses. The first are Oxygen isotope ratios used to reconstruct the temperature of the water during the growth of the shells. A barnacle yielded a range of 15.6-16.8 * C - about 60-61.5 F, quite chilly, but still a bit warmer than the Pacific today off of Washington (7-13 C, or 44-50 *F). The second specimen, a bivalve, yielded a temperature range of 19.9-23*C, or 67-73 *F - considerably warmer than the ocean there today, and actually quite similar to summer water temperature here in San Diego. It's unclear if these estimates reflect analytical error or if the holdfasts are reworked - many of the fossils in the Jansen Creek Member have been reworked into turbidites and deep sea slumps from slightly older deposits on the continental shelf. So, it's possible that some of the dropstones originated from strata representing considerably warmer conditions. These same shells also yielded the first Strontium isotope ratios from the Makah Formation - a powerful indicator of geologic time. The ratio of Strontium 87 and 86 has changed through geologic time, with one becoming more abundant than the other at different points. The ratio is usually somewhere below 1% Strontium 86, and over the course of the Cenozoic, the amount of Strontium 87 has generally been increasing (slightly, and steadily). When the graph fluctuates, the ratio is not useful, but during most of the middle Cenozoic, it increases steadily and therefore is quite accurate. One bivalve sampled for Strontium resulted in a ratio corresponding to a date of 32.1 Mya - or, earliest Oligocene.

Laminaria kelp torn off the rocks during a storm with some large pebbles (5-6 cm diameter) stuck in its holdfast. Santa Cruz, California. Photo by the author.

Southern bull kelp (Durvillaea antarctica) washed ashore on the Otago Peninsula in New Zealand with chunks of rocks stuck to the holdfasts. From Waters and Craw (2017).

Kelp Dropstones

Strong storms during the winter have the capacity to rip kelp off the rocks, and when this happens, the holdfast can rip chunks of rocks that the holdfast was attached to. In some places, this is one of the major drivers of hard rock erosion below the low tide line; southern bull kelp (Durvillaea), for example, bonds so strongly to the rocks that this connection is frequently tougher than the rock itself. Kelp will drift for quite a ways given that the tissue is quite strong and still buoyed up by the pneumatocysts, permitting long-distance transport of drift kelp. Drift kelp has been documented rafting dropstones up to 500 km away from the source; most continental shelves on earth are less than 100 km wide, so intertidal rocks can be dropped into offshore shelf settings, or even onto the abyssal plane - or, making studies of sedimentary petrology potentially confusing - parallel with the shoreline for long distances away from the source area.

Southern bull kelp (Durvillaea antarctica) with potential dropstones - large chunks of rock ripped from the intertidal zone - that ended up on the south coast of the Otago Peninsula. The Murihiku Sandstone is exposed in the Catlins, the southernmost part of the South Island - and the gneiss is from Fiordland, the southwestern corner of the island; this sample must have travelled several hundred kilometers and through the Foveaux Strait. From Craw and Waters (2018).

Geologic map of the southern part of the South Island of New Zealand, showing just how far some of these kelp-rafted rocks traveled to get to the Otago Peninsula. From Craw and Waters (2018).

Experiments in this study by Frey and Dashtgard (2012) indicate that kelp can not only pluck dropstones off the seafloor and float them, but that even small kelp fronds attached to small rocks can transport them simply by pulling them in a light current.

In other cases, even small fronds of small or young kelp attached to loose rocks don't even have to have pneumatocysts or float to transport rocks: water currents can pull these along, the attached kelp acting like a sail, slowly dragging the attached rock across the seafloor. Except in rare cases (see above), it's pretty unlikely that the holdfast itself will fossilize - but as the kelp and its holdfast decay, the rock is left behind. One study of small kelps attached to cobble sized rocks (up to 10 cm) found that these were being actively transported by attached small kelp fronds in the intertidal zone in Washington state in relatively slow tidal currents (0.2 meters per second) that were only able to move 'kelpless' rocks up to 4 cm in diameter (Frey et al. 2012). Other studies have found kelp-transported rocks weighing up to 100 kg being moved onshore during storms.

An isolated pebble (about 3 cm diameter) likely of Salinian granodiorite - the same rocks that make up the Monterey Peninsula - isolated in silty fine sandstone of the Purisima Formation near Half Moon bay, California, in a "middle shelf" setting. The only real way for this pebble to have gotten this far out, without being on an erosional surface, is to have been transported there as a dropstone. Photo by the author.

More dropstones in the same section of the Purisima Formation. Photos by the author.

Fascinatingly, this study predicted that transport of dropstones - either as kelp rafted debris or dragged along the seafloor - would show up in the rock record as isolated large pebbles and cobbles seemingly 'floating' in shelf sandstone deposits. These sorts of deposits, to my knowledge, have not yet been published - but I've been documenting such occurrences in the Purisima Formation of northern California. Unfortunately at present, I don't have much in the way of in situ photographs I've taken in the field, though I'll certainly remedy this in the future.

Kelp dropstones are also potentially quite frustrating as they likely hinder the study of ice rafted debris - a classic example of evidence used to infer glacial paleoclimates.

The fossil record of kelp-associated fauna

Kelp might have a terrible fossil record, but what about the fossil record of some of the groups that have been ecologically associated with kelp forests, past and present?

Live and dead examples of green abalone (Haliotis fulgens) spotted during my tidepooling escapades in southern California. Down here, red abalone (Haliotis rufescens) give way to green as the dominant intertidal abalone; the shells are somewhat smaller, but more brilliantly colored. They generally resemble paua shells from New Zealand (Haliotis iris) - and they branch off one after another on the tree, so perhaps its no wonder they're so similar.

Abalone - Haliotis

Abalones are flat-shelled snails (gastropods) in the family Haliotidae. The interior of the shells have a luxurious mother of pearl nacre that varies in color from species to species, and are highly sought after (I have a decent collection of shells, for example). Abalone have lost their operculum, and there are a series of holes for respiratory pores (and reproductive structures). The foot of an abalone is lined with a bunch of short, radially oriented tentacles. Abalone meat is also highly sought after, and abalone divers here on the Pacific coast need sport fishing licenses and cannot use scuba - all collected abalone must be done so by free-diving (just like a sea otter!) and the shells are pried off with a chisel. The abalone season here has been closed since 2017 owing to declining populations. One house in Inverness, CA, has hundreds, if not thousands, of abalone shells mounted to its exterior and fences.

A fossil example of Haliotis - a relatively small one, some 7-9 cm long or so, from the ~7 myo Monterey Formation of southern California. On display at LACM. Photo by the author.

There are about 70 species today, and all are voracious herbivores. Most are small, from 2-10 cm in maximum shell length, and the red abalone gets to a shocking 30 cm long (my largest examples are about 20-25 cm). Most are cold water species and inhabit the North Pacific (Japan to Baja California), New Zealand, South Africa, and Australia; they are surprisingly absent from the Pacific coast of South America, the western North Atlantic, and, unsurprisingly, absent from the Arctic and Antarctica. Abalone have an extensive fossil record going back to the late Cretaceous, though they are always generally quite rare; a handful of specimens exist in the Pacific coast Neogene, as they tend to be shallow rocky reef inhabitants - environments that are characterized by erosion rather than deposition. Their fossil record does not reveal a center of origin, though they are most diverse in the Indo-Pacific. Tropical species are generally always small, and only cold water species attain large sizes. Large size in general has evolved twice - once in the Pacific clade of Haliotis (including New Zealand Paua, Tropical east Pacific species, and all of our eastern and western North Pacific species) as well as the Australia/South African clade (that's right: NZ Paua, Haliotis iris, is more closely related to eastern North Pacific species than to anything from Australia).

All seven species of abalone native to the temperate Pacific coast of North America - from left diagonally to upper right, top row: pinto abalone (Haliotis kamtschatkana), green abalone (Haliotis fulgens); middle row, from left: flat abalone (Haliotis walallensis), pink abalone (Haliotis corrugata), black abalone (Haliotis cracherodii), bottom row: red abalone (Haliotis rufescens), and white abalone (Haliotis sorenseni). Our shoreline has the highest diversity of abalone species in the world, and almost certainly the highest average body size of abalones - all thanks to our kelp forest ecosystem.

All large bodied species of Haliotis live within kelp forest ecosystems. The rapid growth of kelp has likely permitted these giant body sizes to evolve, both through feeding directly on kelp and also on drift kelp - along with the other algae from the understory in kelp forests. One study proposed that the evolution of kelp forests was a prerequisite for giant abalones to evolve. Further, the "quality" of the kelp matters. North Pacific species of Haliotis - especially red abalone (Haliotis rufescens), pink abalone (Haliotis corrugata) green abalone (Haliotis fulgens) and giant abalone (Haliotis gigantea - though, not as giant as the red abalone!) - are thought to get so much larger than southern hemisphere forms owing to the lower levels of phenolic compounds in kelp. Higher levels in southern hemisphere kelps like Ecklonia might prevent truly gigantic body sizes from evolving (e.g. all of these, even the large H. midae, are smaller than 20 cm). Additionally, the eastern North Pacific - with the largest and most complex kelp forests in the world - has the most diverse fauna of abalones, locally hosting eight species, including the largest (H. rufescens). Shockingly, even our smallest species on the Pacific coast - black (Haliotis cracherodii) and flat (Haliotis walallensis) - are still large species, maxing out at around 15-20 cm long, several times larger than tropical species. Lastly, gigantism likely evolved quite recently. Based on fossils, large body size appears quite suddenly at around the Miocene-Pliocene boundary; all fossil abalones exceeding 10 cm in shell length appear in the Late Miocene or in younger rocks.

Further, body size is quite flexible - a pair of small-bodied sister species in the tropics, Haliotis roberti (Galapagos and tropical east Pacific) and Haliotis pourtalesii (Caribbean and Gulf of Mexico) - evolved from North Pacific species, dispersed south to the tropics before being separated into east and west populations by the uplift of the isthmus of Panama. Despite evolving from large ancestors, they ended up in the tropics where there are no fast growing, gigantic fleshy algae like kelps, and underwent an evolutionary reversal to small body size! Neither species exceeds 5 cm in shell length.

I really do love abalones, and could (and probably should) write a whole blog post on their evolution and fossil record, but I need to keep it brief here. To conclude: gigantism (body length greatly exceeding 10 cm) has only evolved in abalones that live near kelp forests, and suddenly evolved around 5-10 million years ago - likely giving us a decent date for the origin of kelp forests.

A sea otter (Enhydra lutris) eating a clam in Morro Bay. Photo by the author.

Sea otters - Enhydra

Sea otters are today intimately linked with the highly productive giant and bull kelp forests of the North Pacific, formerly inhabiting coastlines from Japan to the Aleutians and southeast to Baja California - but now restricted to the Aleutians, the Alaskan panhandle, British Columbia, and central California (Santa Barbara to Santa Cruz). However, sea otters currently inhabit many sandy shore environments in parts of Alaska and have a bit more environmental flexibility than typically assumed. Though most famous for using tools to smash open sea urchins, crabs, and mollusks - only a subset of sea otters use tools. Tool use does not seem to be correlated with genetics - e.g. otters have a bit of a random chance of tool use in their lifespan - and individual otters will be highly specialized in their feeding habits, but diet is highly variable between individuals. This permits a rather high population density of otters, which can only dive to shallow depths of about 20-30 meters, and thus forage quite close to shore.

Sea otters have been proposed to represent "keystone" species, preying upon herbivorous invertebrates that in turn feed on kelp; without this predation pressure, sea urchin populations get out of control and destroy kelp forests, reducing them to urchin barrens. Where sea otters are absent - places like northern California, Oregon, and part of the Washington coastline - kelp forests have disappeared since the early to mid 19th century when sea otters were nearly hunted to extinction for their furs. Rocky subtidal habitats along the Pacific Northwest coast have been transformed into urchin barren 'deserts'; meanwhile, in California, in areas where sea otters returned, kelp forests proliferated - suggesting a strong link between sea otter population size and kelp forest health.

The oldest known sea otter (Enhydra sp.) from the Pacific Basin - a 620,000 year old femur from the Merced Formation near San Francisco, California. From Boessenecker (2018).

How long has this relationship existed? Sea otters have a surprisingly shallow fossil record in the North Pacific. The earliest sea otter fossil, Enhydra reevei, is based on isolated teeth from the North Sea dating to the early Pleistocene (~2.1 Ma). Slightly younger specimens of Enhydra appear in the basal parts of the Gubik Formation of Alaska (~1-2 Ma), and the oldest Pacific basin record of a sea otter is a complete femur collected by my friend Chris Pirrone from the Merced Formation near San Francisco - and is only about 620,000 years old. These fossils, and the absence of fossils of Enhydra from the very densely sampled upper Pliocene (2-4 myo) San Diego Formation of southern California, strongly suggest a middle Pleistocene immigration of sea otters from the Arctic to the North Pacific. In turn, this indicates that the sea otter > sea urchin > kelp food web is very, very young. Given that kelp has a much older origin than the fossil record of sea otters,

Additionally, I need to mention that there is a somewhat older giant otter, Enhydritherium terraenovae, known mostly from the late Miocene of Florida but also from a few scraps in the latest Miocene and early Pliocene of California. However, this otter has sharp cheek teeth and lacks many of the adaptations for cracking open hard prey seen in extant Enhydra, and ecologically, was much more like a giant river otter; additionally, it is mostly known from nonmarine deposits and is a poor candidate for being an ecological predecessor of Enhydra.

Dusignathine walruses - Dusignathus and Gomphotaria?

The Dusignathinae are an extinct clade of walruses from the eastern North Pacific, basically including only three species, all from California: Dusignathus santacruzensis, Dusignathus seftoni, and Gomphotaria pugnax; these three species are known from the late Miocene Purisima Formation (of Santa Cruz), the Pliocene San Diego Formation (of San Diego), and the late Miocene Capistrano Formation (of Orange County). Scraps have been found in other rock units in California and the Almejas Formation of Baja. All of these have upper and lower canines modified into short tusks, and D. seftoni and Gomphotaria have extensive tooth wear on the cheek teeth and tusks, suggesting ingestion of abrasive material into the oral cavity like sand and silt, which has been interpreted as evidence for a molluskivorous diet. Dusignathus santacruzensis, on the other hand, has an elephant seal or sea lion like dentition lacking evidence for benthic feeding, and was likely a fish eater instead. Prior to most of this evidence being published, the dusignathines were proposed as a possible predecessor of sea otters that could have kept the invertebrate herbivores that decimate kelp beds in check.

However, this is pretty speculative, and it's entirely possible that the tooth wear in these walruses has nothing to do with benthic feeding; I seem to recall that years ago, my colleague Morgan Churchill had some isotopic data suggesting a different mode of feeding ecology. Further, when proposed in 1989, the dusignathines were defined differently, and at the time included mostly fish-eating species like Imagotaria downsi that are now considered to be in different groups within the family. The truth is, we definitely do not know enough about dusignathines to propose them as the ecological progenitors of a modern keystone species. However, dusignathines do predate the fossil record of Enhydra, having a continuous fossil record in California from about 8 Mya to about 2 Mya or so. At least the timing works out - but the paleoecological interpretation requires actual data (e.g. dental microwear, enamel isotopic studies of dusignathines).

The holotype mandible of Kolponomos newportensis found by Doug Emlong in the Nye Mudstone. Smithsonian collections. Photo by the author.

The "Beach Bear" - Kolponomos

Kolponomos is an unusual marine carnivore known from the earliest Miocene Clallam Formation of Washington and the Nye Mudstone of Oregon - there are a few decent specimens, of which Kolponomos newportensis from Oregon is the best known. I've held and examined the holotype skull at the Smithsonian - it is a wondrous specimen. Similar to a bear skull in many ways but with wide zygomatic arches (and therefore powerful jaw closing muscles), it is also studded with expanded, wide, teeth with thick enamel - almost exactly what you would predict if a bear like carnivore were to adapt to a sea otter like diet. Unlike sea otters, the mandibles are fused at the chin, indicating a somewhat different mode of crushing prey items (likely using both left and right teeth at the same time, instead of one side as in otters). Kolponomos has been proposed to occupy the sea otter niche in the eastern North Pacific and could have fostered kelp forest health early on. However, there are really only a handful of specimens, suggesting only a short geologic range - just a couple million years in the early Miocene. It's possible, but not something I'd hang my hat on.

A giant kelp fish (Heterostichus rostratus) that is certainly kelp colored to match the kelp fronds. Monterey Bay Aquarium. Photo by the author.

A giant kelp fish (Heterostichus rostratus) really blending in well amongst the algae on the rocks near San Diego, California. Photo by the author.

A spotted kelpfish (Gibbonsia elegans), amongst the algae near San Diego, California. Photo by the author.

Kelpfish - Heterostichus and Gibbonsia

Kelpfish are a group of fish within the 'blennies' (Blenniiformes - a rather cute group of fish often with distinctive branched "eyebrow" cirri that inhabit burrows and crevices) that have evolved to favor living in and amongst kelp, including some species in the genus Gibbonsia and especially the giant kelpfish, Heterostichus. There is no fossil record for any of these, and, surprisingly, little research on their evolution (including molecular clock divergence) has been attempted. I suspect that otoliths (ear stones) of these fish might be found at some stage.

A rather large northern kelp crab (Pugettia productus) fumbling around in the seagrass at low tide.

Another type of kelp crab, one that is a sort of decorator crab - the graceful kelp crab, Pugettia gracilis. These don't get quite as large, and they are difficult to spot.

A juvenile northern kelp crab, Pugettia productus, which has stuck a bit of kelp to its rostrum. Apparently these bits are held in place rather than affixed to the exoskeleton and growing on it.

Kelp Crabs - Pugettia

There are a number of species of crabs in the familiy Majidae that have evolved to live in and feed on kelp and other algae - though they are not strictly kelp inhabitants - and in the winter, they tend to be more omnivorous to carnivorous, feeding on other invertebrates as the winter storms tend to rip some of the kelp away. Kelp crabs include two genera here in the eastern North Pacific - Pugettia, and Taliepus- the most common example of each are the northern kelp crab (Pugettia producta) and the southern kelp crab (Taliepus nuttallii). Only Pugettia has a fossil record - the northern kelp crab, Pugettia producta, and the cryptic kelp crab, Pugettia richii, are both reported in one of Mary Rathbun's monographs, from numerous Pleistocene localities in southern California, including the San Pedro Sand. Unfortunately, these fossils weren't figured, and in any event are geologically too young to inform this discussion.

Feather boa kelp (Egregia menziesii) has a flat stipe similar in size, shape, and honestly, flexibility/stiffness as a leather belt; several limpets can often be found slowly rasping away at the stipe. On the left is one that is comically chewed up by limpets, and on the right, is what I am reasonably certain is a seaweed limpet, Discurria insessa.

Limpets - Discurria and Lottia

Limpets (Patellogastropoda) are surprisingly rare in the Pacific coast fossil record, though their low conical shells are very common on intertidal rocks here. All are herbivorous, and while most live on rocks and graze algae and diatomaceous films, others have evolved to live perpetually on seagrass blades and on kelp. Seagrass limpets have very narrow, long shells, whereas kelp limpets have slightly narrow, saddle shaped shells to conform to the kelp stipe. Both seagrass and kelp limpets have evolved multiple times in parallel, and in the eastern North Pacific, there are kelp limpets in both the genera Lottia (L. pelta) and Discurria (D. insessa). These species appear as fossils during the late Pliocene, about 3 Mya - and saddle-shaped limpets do not appear in the fossil record any earlier. This has been underlined by some studies that perhaps canopy kelps did not evolve until the Pliocene. However - we generally don't have much of a fossil record of rocky shore environments, at least along the Pacific coast, from rocks that are any older than the Pliocene, and most are known from the Pleistocene. Is this reliable, or an example of "pull of the recent"?

Purple urchins (Strongylocentrotus purpuratus) in their typical habitus: embedded in spherical borings in the rock, waiting to catch pieces of drift kelp with their tube feet. So long as they stay in their borings, kelp forests can prosper. The smooth rocks are actually 'captured' by the urchins and held in place by tube feet, a sort of layer of armor against predators. Fitzgerald Marine Preserve, California. Photo by the author.

Perhaps my only sighting of a red urchin - Mesocentrotus franciscanus - these tend to live deeper than purple urchins and are difficult to find while tidepooling. Being only subtidal, this one I spotted about a meter below 0 while snorkeling in San Diego. Photo by the author.

A purple urchin (Strongylocentrotus purpuratus) and its reflection in a San Diego tidepool. Photo by the author.

An absolutely incredible specimen - a gigantic test (shell) of a red urchin, Mesocentrotus franciscanus, spotted recently at the Charleston Marine Life Center in Oregon. Photo by the author.

Purple and Red Sea urchins - Strongylocentrotidae

The Strongylocentrotidae are a family of sea urchins including the infamous purple urchin (Strongylocentrotus purpuratus) of the eastern North Pacific, and the larger red urchin, Mesocentrotus franscicanus (also from the Pacific coast). These urchins are herbivorous and, along the Pacific coast, tend to be sessile and excavate spherical borings and catch bits of drift kelp with their tube feet - at least in areas where there is plenty of drift kelp. If kelp becomes rare, they will leave their borings and become more mobile, grazing directly on live algae and kelp and causing the proliferation of urchin barrens. The sheer majority of strongylocentrotid species live in or adjacent to kelp forest habitat (or, former kelp forests) and feed either on drift kelp and other drift algae, or directly on macroalgae. The modern clade of North Pacific forms evolved mostly in the past 5-6 million years, surprisingly similar to the origin of gigantism in abalones (Haliotis; see above) and gigantism and toothlessness in sea cows (Hydrodamalis; see below). I suspect that the origin of these urchins in the eastern North Pacific around the end of the Miocene indicates the timing of initial kelp forest expansion.

Sea cows - Hydrodamalis (and Dusisiren?)

The gigantic sea cows of the Hydrodamalinae are unique to the North Pacific, and include two genera: Dusisiren and Hydrodamalis, which likely form an ancestor-descendant relationship, and culminated in the recently extinct Steller's sea cow, Hydrodamalis gigas. This gigantic relative of the manatee and the dugong of the tropics attained lengths of 7-8 meters, was completely toothless, lived in herds, and grazed chiefly on algae including sieve kelp (Agarum), bull kelp (Nereocystis), cup-and-saucer algae (Constantinea), and winged kelp (Alaria). These are all either short algae that can be accessed in shallow waters, or floating forms that with pneumatocysts that reach the surface. Despite being extinct, these sea cows were observed in detail by G.W. Steller when the ship St. Peter of the Bering expedition was shipwrecked in the Komandorskiye Islands, southwest of the Aleutians and east of Kamchatka. Critically, Hydrodamalis gigas lacked teeth - instead, there were keratinous (horny) pads on the palate for crushing the relatively soft tissues of fleshy kelps and other macroalgae. (Domning, 1978, points out that these are the same horny pads in front of the cheek teeth in other sirenians, and that they simply expanded further posteriorly in Hydrodamalis gigas, rather than replacing the teeth, which is a common misconception).

The titanic skeleton of Hydrodamalis cuestae, the largest sea cow to ever evolve, on display at the San Diego Natural History Museum. This skeleton is known from the Pliocene San Diego Formation of California. Photo by the author.

Extinct species of hydrodamalines further illuminate the evolutionary heritage. There are several species of Dusisiren, the best known of which is the ~4 meter long Dusisiren jordani from the Santa Margarita Sandstone and Monterey Formation of California; this resembled a gigantic tuskless Metaxytherium from the Atlantic, and likely evolved from Metaxytherium - perhaps something like M. arctodites from the middle Miocene of southern California and Baja. Though lacking tusks, Dusisiren jordani retained a full complement of adult teeth; additionally, the rostrum is not deflected, which in concert with the lack of tusks, suggests feeding upon seagrasses (or algae) in the water column. Dusisiren dewana is the very first hydrodamaline to disperse westward across the North Pacific rim to Japan, and is known from the latest Miocene of California as well; this species gave rise to Hydrodamalis cuestae, the largest sirenian ever, and the presumed direct ancestor of Hydrodamalis gigas.

An enormous skull of Hydrodamalis cuestae from the 2-4 Ma (Pliocene) San Diego Formation of southern California - perhaps the largest individual sirenian ever. On display at the San Diego Natural History Museum. Photo by the author.

Hydrodamalis cuestae was originally reported from the Pismo Formation of central California, and subsequently from the San Diego (early to late Pliocene) and San Mateo Formation (late Miocene and early Pliocene) of San Diego County. I've even discovered some pieces of this animal in the Purisima Formation at Point Reyes. Hydrodamalis cuestae is quite interesting because it is nearly double the length of Dusisiren jordani despite being just a few million years younger - indicating quite the increase in body length between ~8-9 Mya and 3-5 Mya; the largest known skull of Hydrodamalis cuestae is the titanic specimen SDSNH 90767, perhaps reflecting a formidable beast measuring up to 10 meters in body length. This incredible skull is on display at the San Diego Natural History Museum. Perhaps more critical than its stupendous size is the fact that Hydrodamalis cuestae is the first toothless sea cow - juveniles retained vestigial cheek teeth, but adult specimens lack them entirely, just like the recently extinct Steller's sea cow. Kelp is quite soft and decidedly non-gritty, and does not require much chewing. In fact, Steller both wrote that the sea cows chewed their food, but also that large pieces of intact kelp were present in the guts of dead individuals - perhaps suggesting that they simply snagged pieces of kelp right off the stipe and swallowed it whole without much chewing.

By the time of discovery by European explorers, Hydrodamalis gigas only lived in the shallow waters around the uninhabited Komandorskiye Islands. Subfossil and some historical evidence indicates that Hydrodamalis inhabited parts of the Western Aleutians (Near Islands, Rat Islands, Andreanof Islands) into the past 2,000 years and overlapped for thousands of years with the first aboriginal humans to arrive on these islands. Pleistocene fossils indicate a near circum North Pacific distribution for Hydrodamalis gigas, from southern California to Japan - and by the early Holocene, the population was restricted to the northernmost Pacific. Ecological modeling suggests that, even if aboriginal hunters did not even target Hydrodamalis in the Aleutians, overhunting of sea otters would have led to the loss of kelp forests and could have driven the majority of range loss of Hydrodamalis all on its own.

Overall, it seems as though hydrodamalines evolved toothlessness and gigantism right around the Miocene-Pliocene boundary, similar in timing to the gigantism of abalones and the diversification of strongylocentrotid urchins.

A Desmostylus mandible on display at the Natural History Musuem of Los Angeles in the "LA Underwater" exhibit. Photo by the author.

Desmostylians - Desmostylus and Neoparadoxia

The bizarre desmostylians are a group of extinct four-legged, somewhat hippo-like herbivorous marine mammals that are either most likely related to elephants and sirenians in the Afrotheria/Tethytheria or possibly to rhinos in the Perissodactyla; their teeth are so highly derived, that it's nearly impossible to know at present (we need more ancestral forms). These strange marine mammals can get quite large - skulls up to, and even exceeding a meter - and have upper and lower tusks that protrude from the mouth, along with a series of bizarre premolars and molars that look like a bunch of cylinders bound together; the most stereotypical teeth look like six packs of beer cans (or like a package of sushi rolls). Their fossil record is best sampled in California and especially Japan, where there are even some cartoon desmostylian mascots; in fact, it's quite clear that desmostylians are quite possibly the most emblematic of the Japanese fossil record as they're found throughout the country and on display in most natural history museums. There are a few genera - Desmostylus, "Vanderhoofius", Ounalashkastylus, Paleoparadoxia, and Neoparadoxia from the early through late Miocene (Neoparadoxia is classically only middle to late Miocene), and Ashoroa, Behemotops, Seuku, Cornwallius, and Archaeoparadoxia from the late Oligocene and earliest Miocene. All of these have similar dentitions.

While desmostylians are clearly not carnivores, they have been proposed to have been molluskivorous in the past. Their strange teeth, and lack of commonality with tooth wear seen in land mammals, has stymied attempts to interpret their feeding ecology from dental microwear. Desmostylus hesperus has, however, been sampled for oxygen isotopes. These isotopic ratios indicate that it mostly fed in shallow waters, likely to be estuaries and embayments- but nearly exclusively ate aquatic vegetation, likely seagrasses, but also possibly some algae like sea lettuce (Ulva spp.). The paleoparadoxiids Paleoparadoxia and Neoparadoxia have not yet been studied isotopically, but in the Japanese rock record, are nearly always found in deeper water rocks than Desmostylus - perhaps indicating that Paleoparadoxia and Neoparadoxia would have been more likely to feed on kelp, which grows in much deeper waters than seagrasses do.

The holotype skeleton of the geochronologically late desmostylian Neoparadoxia cecilialina from the upper Miocene Monterey Formation of Orange County. On display at NHM Los Angeles. Photo by the author.

As for a specific diet beyond marine herbivory - the jury's still out regarding kelp or seagrass as the major food for desmostylians. Did they feed on kelp? Daryl Domning wrote in his earlier studies that because desmostylians immigrated eastward from the coast of Asia during the late Oligocene, and that hydrodamaline sea cows did not immigrate westwards from the east Pacific until the latest Miocene, that desmostylians must have had a higher tolerance for cold climates; no doubt their semiaquatic habitus must have helped. Did desmostylians and hydrodamalines compete? Certainly, at some level - but since they coexisted with sirenians for much of the Miocene, it seems unlikely that they were outcompeted by hydrodamalines. On the contrary, Domning considered that desmostylians may have driven the tusked sirenian Dioplotherium to extinction in the middle Miocene. Cooling of the Pacific in the late Miocene seems to be an unlikely cause for their extinction, as they traversed the North Pacific quite early.

However, the extinction of desmostylians does coincide with the evolution of gigantism in hydrodamalines. Could the later species of Dusisiren have outcompeted desmostylians for food? Depending upon how little area was colonized by kelp, it's possible. Domning notes that gigantism doesn't seem to evolve until after the last desmostylians become extinct - indeed, Dusisiren dewana is the hydrodamaline that co-exists with the geochronologically latest desmostylians. I do find it troubling, if desmostylians were eating kelp, that they never evolved toothlessness (though gigantic sizes were attained by some desmostylians which had shed their last teeth; Santos et al. 2016). This to me suggests a sustained contribution of seagrasses. Perhaps the middle to late Miocene cooling that resulted in a proliferation of kelp, and likely caused a contraction in the size of seagrass beds - could explain both the size increase and development of toothlessness in hydrodamalines, and the extinction of desmostylians?

Blacksmith damselfish (Chromis punctipinnis) amidst a tangle of kelp in a tank at the Monterey Bay Aquarium. Photo by the author.

Future Directions and Unanswered Questions

1) Who fed on marine invertebrates prior to the middle Pleistocene arrival of sea otters?

This is a major paradox in the otters as keystone species hypothesis for Pacific coast kelp forests. Otters very much seem to foster kelp forest health today - though their fossil record is quite shallow, only seeming to have been here for slightly longer than half a million years - less than one twentieth the time since the Macrocystis-Nereocystis clade diverged in the late Miocene. So, what species might have kept the voracious appetites of sea urchins and abalones at bay prior to the Pleistocene? A few studies have proposed that dusignathine walruses during the Late Miocene and Pliocene may have fulfilled that role, and Kolponomos in the earliest Miocene. This is admittedly speculative, as the diet of dusignathines has not been studied in detail, and the jury's out as to what they were feeding on. Further, there are rather long gaps in between the fossil records of these taxa. Strongylocentrotid urchins may not have even existed along the Pacific coast until the late Miocene - so it's possible that invoking Kolponomos is not necessary. Additionally, Enhydritherium is known from a couple of latest Miocene to early Pliocene scraps from California, but this species was likely not dentally equipped for feeding on kelp forest invertebrates.

Is it possible - and this is going to sound uncharaceristically anti-mammal for me for once - that we've been ignoring other invertebrate predators? Sea otters are not the only durophagous predators of marine invertebrates along our coast. Many of these predators are fish and some are even invertebrates.

A wolf eel (Anarrichthys ocellatus) in a tank at the Monterey Bay Aquarium. Photo by the author.

A) Wolf eels (Anarrichthys ocellatus) are quite large (2 meters, up to 15-20 kg), have conical teeth in front and blunt, molar-like teeth in the back of the jaw and feed on mollusks, sea urchins, and crustaceans as adults. They live exclusively on rocky bottoms from Alaska to northern California. These fish also have a longer fossil record in the North Pacific, going back to at least the early Pliocene. Interestingly, these fish evidently eat so many urchins that they can also get echinochrome staining in their teeth and bones, just like sea otters!

A California horn shark (Heterodontus francisci) hunting through the red algae for crustaceans and other invertebrates to eat. La Jolla, California. Photo by the author.

B) Horn sharks (Heterodontus francisci) live along the California coast today, from near the Oregon border down to Baja and nearly to Puerto Vallarta. These tubby, cute little sharks grow to about a meter and have a dentition that is functionally similar to wolf eels; juveniles prefer soft bottom, but adults prefer rocky bottoms including kelp forests. And, they have a nearly identical diet to wolf eels. The horn sharks are an ancient lineage as far as modern shark species are concerned, and molecular clock dating suggests that our species here in California waters diverged from other lineages during the Eocene, about 43 Mya.

A juvenile bat ray (Myliobatis californica) in the touch tank at the Monterey Bay Aquarium. Photo by the author.

C) The bat ray (Myliobatis californica) lives on sandy and rocky bottoms from Oregon to southern Baja California and females attain diameters of nearly two meters and weigh up to 90 kg. Like wolf eels and horn sharks, it mostly feeds on mollusks, urchins, and crustaceans - throughout its life span - using the flat table-like crushing tooth plates common in bat and cownose rays. Myliobatis has been on the California coast for tens of millions of years. Additionally, there are several other species of durophagous rays including some species of guitarfish and stingrays, though admittedly they have a somewhat higher degree of a piscivorous diet.

A terminal phase California sheepshead (Semicossyphus/Bodianus pulcher) in the kelp forest tank at the Monterey Bay Aquarium. Photo by the author.

D) The California sheepshead, Semicossyphus pulcher (or, more recently, in the genus Bodianus) - one of our most famous marine fish - is a giant wrasse that lives from Monterey to southern Baja, grows to about a meter and 15 kg, and feeds chiefly on sea urchins, mollusks, and crustaceans. The jaws are lined with some conical caniniform teeth and a bunch of low crowned onion shaped teeth, which are not much use in crushing - but instead, has some massive pharyngeal tooth plates constructed out of many little spheres of enamel - essentially, crushing plates that are in the fish's throat. The crushing plates are common in the Santa Margarita Sandstone and other late Miocene through Pleistocene fish bearing deposits in California.

A massive sunflower star, Pycnopodia helianthoides. Photo by Marco Mazza.

E) The sunflower star (Pycnopodia helianthoides) is the world's largest sea star, growing up to a meter in diameter, and weighing in at about 5 kg. These sea stars formerly lived from Alaska to southern California, but sea star wasting disease has reduced their range south of British Columbia. Nevertheless, these are voracious predators of sea urchins. They do not have a fossil record, and I don't know how old the lineage is based on molecular clock divergence.

An ochre star, Pisaster ochraceus, found on the beach in Half Moon Bay - very much still alive, so I gave it a gentle toss into the surf zone. Probably a bit far away from rocky substrate - who knows how it washed up here. Photo by the author.

F) The giant pacific sea stars (Pisaster spp.), including the ochre star (Pisaster ochraceus), giant sea star (Pisaster brevispinus), and the giant pink sea star (Pisaster brevispinus), all get quite large (up to 25 cm in the ochre star, 40 cm in the giant, and 60 cm in the giant pink sea star) and live from Alaska to southern California or Baja. All feed on mollusks, but the ochre star in particular lives on the most violently active rocky shores and is similarly viewed as a keystone species for preying upon sea urchins - though tidepoolers will most likely see these going after California mussels. The other two species, though larger, tend to avoid open coast settings and prefer more gentle embayments. Unlike the sunflower star, the giant Pacific sea stars of the genus Pisaster do have a fossil record, and are known from the early Pliocene and late Miocene parts of the Purisima Formation (though these fossils are undescribed).

My most active giant pacific octopus (Enteroctopus dofleini) sighting in an aquarium ever, at the Steinhart Aquarium, California Academy of Sciences in San Francisco, California. Photo by the author.

G) And lastly, how could we forget the world's largest octopus? The Giant pacific octopus (Enteroctopus dofleini) lives mostly on rocky bottoms from the low tide line to 2,000 meters, and has a circum-North Pacific distribution from the East China Sea north to Japan and the Aleutians, and south through Alaska, British Columbia down to California and northern Baja. These eat all sorts of mollusks, crustaceans, sea urchins, and fish. Unfortunately these animals are basically all soft tissue and we have no fossils of them - though perhaps gigantic sized octopus feeding traces of the ichnogenus Oichnus could be found and attributed to Enteroctopus; the Enteroctopus lineage (which includes other smaller species) diverged from other members of the same family during the earliest Miocene or Oligocene.

In sum, there are numerous other non-mammalian species that we known have existed along the Pacific coast for millions of years that have diets that overlap completely or considerably with sea otters - or, likely existed along our coastline owing to molecular clock analyses (for the gooeyest species lacking a fossil record, that is). How much of the sea urchin biomass these species are responsible for dispatching is an open question - though it is worth noting that urchin barrens have considerably expanded in the wake of sea star wasting disease, which most heavily affected the sunflower and ochre stars - suggesting that these species are also, indeed, keystone species like sea otters.

2) Is our fossil record of kelp-associated species good enough to say anything conclusive about the proliferation of kelp forests?

This is truly an existential question of the sort that keeps - or, should keep - invertebrate paleontologists and paleobiologists awake at night. It's an easy question for taphonomists to ask, but an incredibly difficult question to answer. In essence: kelp forests typically only occur on rocky bottoms, and rocky bottoms are characterized by erosion, rather than deposition. While fossils do often get concentrated in thin strata representing periods of time of mild erosion, severe erosion that might expose bedrock on the seafloor as well as form cliffs and sea stacks - like the sheer majority of the modern California coastline - tends to result in wave action that is so strong that shells and bones alike are typically abraded down to little pebbles. I'm going to highlight, and contrast, two relevant rock units.

The first is the Purisima Formation of northern California. The Purisima Formation was deposited in a series of two or three different and relatively small basins around proto-Monterey Bay, and though it starts off as an offshore deposit in the latest Miocene, by the early Pliocene parts of the unit it reflects considerable shallowing to inner shelf settings (under 15 meters deep). None of the basins could have been so vastly large that rocky shore settings - if they existed - would have been more than 10-15 kilometers away. The Pliocene coastline was probably considerably sandier than now, and may not have had any cliffs - instead resembling the sandy shoreline present closer to Watsonville and south to Fisherman's Wharf in Monterey. There are virtually no fossils of kelp forest inhabitants in the Purisima: no kelp crabs, no abalone - though there are some kelp forest-adjacent gastropods (Tegula) and clams (Saxidomus) - or rocky shore environments including ochre stars (Pisaster) and mussels (Mytilus). There are erosional surfaces in the Purisima that have hard bottom - but were likely too deep to support kelp beds, and in any event, all of the calcium carbonate is gone. Lastly, there is some evidence of kelp along the periphery of the basin in the form of possible kelp dropstones (see above). This is largely consistent with a growing body of taphonomic evidence that suggests that invertebrate fossil assemblages are, in a spatial sense, very reflective of the original ecology: simply put, mollusk shells don't move around too much, at least not out of their original depositional environment. Inner shelf sandy bottom mollusks tend to stay in that environment and not end up in kelp forests (or the outer shelf, for that matter). The Purisima Formation - reflecting a predominantly soft bottom environment, with occasional evidence of kelp forests nearby - probably reflects the majority of the rock and invertebrate fossil record, at least on the Pacific coast.

The second is the Moonstone Beach Formation of northernmost California. This unit is not widespread and is only preserved as small lenses between rocky headlands, and occasionally even as sedimentary fill within rocky subtidal crevasses - likely representing sandy deposition within surge channels between masses of Franciscan Complex bedrock. It is quite densely fossiliferous, and has produced a pretty phenomenal fossil assemblage for such a small outcrop, including tons of mussels (Mytilus), barnacles (Megabalanus), keyhole limpets (Cranopsis, Diodora), chitons (Mopalia, Tonicella, Ischnochiton, Lepidochiton, Lepidozona), gooseneck barnacles (Pollicipes), a snail associated with feather boa kelp (Collisella), intertidal snailes (Littorina), kelp crabs (Pugettia gracilis), a lithodid crab associated with calcareous algae (Oedignathus inermis), and three species of urchins including the purple (Strongylocentrotus purpuratus), red (Mesocentrotus franciscanus), and green urchin (Strongylocentrotus droebachiensis). And, of course, there is the extinct sea otter, Enhydra macrodonta, known from the unit as well. In addition to the geomorphologic evidence of the bedrock and crevice and channel infill style deposition of the Moonstone Beach Formation, there is simply copious evidence from the fauna that there was a rich kelp forest habitat right there - unlike the Purisima Formation.

There's only one problem with the Moonstone Beach Formation. It's very young - only middle Pleistocene in age, perhaps 500,000 years. The cliffs were likely eroded during the Marine Isotope Stage 11 marine highstand, and coastal uplift raised the "bathtub ring" deposits of the Moonstone Beach formation about 20-30 meters up, just far enough to prevent further erosion. The deposit itself is not very voluminous and the outcrops themselves are very small and difficult to access, let alone even find, now that many are becoming increasingly overgrown. Accessing one deposit is a bit like an adventure from The Goonies - unless you want to swim, you need to wait for a minus tide in the winter or spring, walk out along a sandbar that remains shallowly submerged (taking care not to fall into a surge channel as I did), walk to a sea stack, find a cave underneath, walk through and around to the top where the unit fills a 3-4 meter wide crevasse - all the while trying not to accidentally step on baby seabirds.

The point of all this is that if the Moonstone Beach Formation was any older, it would either likely be completely eroded away after a couple of million years, or be completely buried. There very well might be deposits of the Purisima Formation that are rocky shore settings - but those are along the margins of the basins where the Purisima sediments meet the ancient shoreline - and are probably still deeply buried. Once exposed by natural erosion, however, these deposits likely don't last very long. Rocky shore environments, at least on the Pacific coast, are probably quite ephemeral - virtually all of our rocky shore fossil assemblages, as a result, are all from the middle and late Pleistocene. What this means is - the sudden appearance of many kelp associated invertebrates in the Pliocene and Pleistocene might simply reflect the fact that most of our rocky shore deposits happen to be extremely young and therefore might be considerably biased (e.g. the limpets mentioned above).

3) Will we find more kelp holdfasts and fossil kelp?

I damn well hope so. I think further fieldwork is needed, and in units like the Purisima Formation - where fossil baleen has been preserved, and fossilized skate cartilage is common - there's probably a high capacity for preserving kelp holdfasts if we know where to look. I've never spotted something like a branching holdfast, but I never thought something like that could fossilize - so now I'll really be paying attention.

Why haven't there been any studies on Monterey Formation macroalgae since the 1960s? The collection reported by Parker and Dawson (1966) is quite large - surely, museums like LACM must have continued fieldwork in some of these localities. I suspect that there is probably more fossil kelp awaiting discovery, or that some might even be sitting in museum collections somewhere awaiting study.

4) Can we find more indirect evidence of kelps, such as dropstones?

I actually think this has a lot of promise. There are only so many ways to get large stones into middle and outer shelf deposits - kelp rafting/dragging, and gastroliths in some birds and pinnipeds. I'd wager that kelp is considerably more abundant than any gastrolith producing vertebrates. Even a field survey reporting on the stratigraphic pattern of kelp dropstones could be informative - do these stones appear suddenly during the late Miocene? A careful analysis could highlight such a pattern.

5) Do kelp holdfasts leave any traces on rocky or shelly substrate?

This is a question for an ichnologist to figure out. If there is some signature or trace fossil that kelp holdfasts might leave behind, this could further expand our search for evidence of kelp forests.

6) And lastly, what drove the evolution of rapid kelp growth?

This is admittedly a chicken and the egg question that is typically quite difficult to answer in paleobiology - but, is it possible that intense herbivory drove the rapid growth of kelp, and not the other way around? In other words - is it possible that things like desmostylians, hydrodamaline sea cows, strongylocentrotid sea urchins, and abalones could have triggered the unique growth pattern of kelps? The rather ancient (e.g. Eocene-Oligocene) origin of Laminariales suggests against this, but the truly rapid growth rates seen in the canopy kelps that have a more recent phylogenetic origin could have been influenced by intense herbivory during the Miocene.

A special thank you to "Piranha" on thefossilforum.com for providing me with a much-needed pdf of Parker and Dawson (1965).

References and Further Reading

Boessenecker 2018. A Middle Pleistocene Sea Otter from Northern California and the Antiquity of Enhydra in the Pacific Basin. Journal of Mammalian Evolution 25:27-35. https://link.springer.com/article/10.1007/s10914-016-9373-6

Clementz et al. 2003. A paleoecological paradox: the habitat and dietary preferences of the extinct tethythere Desmostylus, inferred from stable isotope analysis. Paleobiology, 29:506-519. https://www.cambridge.org/core/journals/paleobiology/article/abs/paleoecological-paradox-the-habitat-and-dietary-preferences-of-the-extinct-tethythere-desmostylus-inferred-from-stable-isotope-analysis/88512187D088C94D924BFF0ACEE78B43

Craw and Waters 2018. Long distance kelp-rafting of rocks around
southern New Zealand, New Zealand Journal of Geology and Geophysics, 61:428-443. https://rsnz.onlinelibrary.wiley.com/doi/10.1080/00288306.2018.1492424

Domning 1978. Sirenian evolution in the North Pacific Ocean. University of California Publications in Geological Sciences 188:1-176.

Domning 1989. Kelp evolution: a comment. Paleobiology, 15:53-56. https://www.cambridge.org/core/journals/paleobiology/article/abs/kelp-evolution-a-comment/51069F5673A8EB585E1C19661E231D1C

Domning et al. 2007. Steller's sea cow in the Aleutian Islands. Marine Mammal Science 23:976-983. https://onlinelibrary.wiley.com/doi/10.1111/j.1748-7692.2007.00153.x

Estes and Steinberg 1988A. Predation, herbivory, and kelp evolution. Paleobiology 14:19-36. https://www.cambridge.org/core/journals/paleobiology/article/abs/predation-herbivory-and-kelp-evolution/8BD83F331294C4B30E470A301660624E

Estes and Steinberg 1989. Response to Domning. Paleobiology 15:57-60. https://www.cambridge.org/core/journals/paleobiology/article/abs/response-to-domning/55141B6BE582E02693DB4010D6C6D359

Estes et al 2005. Evolution of large body size in abalones (Haliotis): patterns and implications. Paleobiology 31:591-606. https://www.cambridge.org/core/journals/paleobiology/article/abs/evolution-of-large-body-size-in-abalones-haliotis-patterns-and-implications/530B5BCEF0273104082B3B779E4E834F

Frey et al. 2012. Seaweed-assisted, benthic gravel transport by tidal currents. Sedimentary Geology 265-266:121-125. https://www.sciencedirect.com/science/article/abs/pii/S0037073812001005

Geiger and Groves 1999. Review of fossil abalone (Gastropoda: Vetigastropoda: Haliotidae) with comparison to recent species. Journal of Paleontology 73:872-885. https://www.cambridge.org/core/journals/journal-of-paleontology/article/abs/review-of-fossil-abalone-gastropoda-vetigastropoda-haliotidae-with-comparison-to-recent-species/D2BCDF9E75306D14955DE0C202F9F25D

Kawai et al. 2013. Ancestral reproductive structure in basal kelp Aureophycus aleuticus. Scientific Reports 3:2491. https://www.nature.com/articles/srep02491

Kenyon 1969. The sea otter in the eastern Pacific region. North American Fauna 68: 1-352. https://digital.library.unt.edu/ark:/67531/metadc700973/

Kiel et al. 2024. Early Oligocene kelp holdfasts and stepwise evolution of the kelp ecosystem in the North Pacific. Proceedings of the National Academy of Science 121:e2317054121. https://www.pnas.org/doi/10.1073/pnas.2317054121

Lee 2003. Molecular phylogenies and divergence times of sea urchin species of Strongylocentrotidae, Echinoidea. Molecular Biology and Evolution 20:1211-1221. https://academic.oup.com/mbe/article/20/8/1211/1081403

Rathbun 1926. The fossil stalk-eyed Crustacea of the Pacific Slope of North America. United States National Museum Bulletin 138:1-149. https://www.biodiversitylibrary.org/page/8429305

Santos et al. 2016. New data on the ontogeny and senescence of Desmostylus (Desmostylia, Mammalia). Journal of Vertebrate Paleontology 36:e1078344. https://www.tandfonline.com/doi/full/10.1080/02724634.2016.1078344

Sarko et al. 2010. Estimating body size of fossil sirenians. Marine Mammal Science 26:937-959. https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1748-7692.2010.00384.x

Starko et al. 2019. A comprehensive kelp phylogeny sheds light on the evolution of an ecosystem. Molecular Phylogenetics and Evolution 136:138-150. https://www.sciencedirect.com/science/article/abs/pii/S1055790319300892

Vermeij 2012. The evolution of gigantism on temperate seashores. Biological Journal of the Linnean Society 106:776-793. https://academic.oup.com/biolinnean/article-abstract/106/4/776/2452394

Vermeij et al. 2018. The coastal North Pacific: origins and history of a dominant marine biota. Journal of Biogeography 46: 1-18. https://onlinelibrary.wiley.com/doi/10.1111/jbi.13471

Waters and Craw 2017. Large kelp-rafted rocks as potential dropstones in the Southern Ocean. Marine Geology 391:13-19. https://www.sciencedirect.com/science/article/abs/pii/S0025322717302025

Nudibranch hunting in southern California

2026-05-27T16:50:24.093-07:00

Since my last post before moving to southern California was all about looking for nudibranchs in Northern California, I thought I'd follow it up and write about my experiences looking for nudibranchs down here. In the spirit of being inclusive I'm going to be discussing sea slugs in general, not just nudibranchs, since I've had very good luck spotting non-nudibranch sea slugs down here.

Differences between northern and southern California tidepooling

Before we start with photos, I need to cover some basics. Southern California, for the purposes of this post, is defined as everything southeast of Point Conception west of Santa Barbara. For any geologists reading, this is the western end of the Transverse Ranges - the formidable wall that separates the LA basin to the south from the coast ranges, San Joaquin Valley, and Mojave desert to the north. Geologically speaking, the transverse ranges form a rather nice barrier as well. Politically and historically speaking, the boundary might be placed somewhat further North - but climatically speaking, everything north of Santa Barbara is much more similar to northern California. Coastal chaparral gives way to coastal scrub, redwood groves begin appearing, summertime temperatures are much cooler, and of course, wine country starts just over the hill from Santa Barbara. The mountains begin to look green year round instead of brown.

These changes are all associated with the marine climate and ocean currents of our coast. The California current is a north-to-south cold water current - the direct opposite of the Gulf Stream in the Atlantic. This cold current brings chilly water from Alaska far south, and for the most part, is pretty close to the coast - until it reaches Point Conception. At that point (no pun intended) it continues south instead of bending east towards Santa Barbara, essentially forming a gigantic eddy between Santa Barbara and San Diego. Warm water from the west coast of Baja is transported north, keeping the water here "warm". I'll level with you: the water temperature here in San Diego typically peaks around 70F - about 10 degrees colder than the coldest it ever gets in the Florida keys. It's just warm enough to swim without a wetsuit for a month or two, and even then, it's still pretty chilly. Last fall (September 2025) it peaked at about 74F, which was pretty nice for snorkeling.

Not a nudibranch, but an enormous sea slug - Navanax inermis, a headshield slug (Cephalaspidea). It's typical to see small, juvenile specimens 2-6 cm long in tidepools, but these colorful predators get up to 25 cm; this is about a 15 cm long individual I saw while snorkeling. You pretty much need to go snorkeling or diving to see the big ones.

Comparing San Diego to the Florida Keys is unfair, so let's pick a couple points at the same latitude on each coast. Half Moon Bay, California - the place where I first (very briefly) swam in the ocean - tops out around 60F in August, whereas in Virginia Beach (VA) on the Atlantic coast, the water gets up to 80F. Summer sea surface temperatures are similar to Half Moon Bay further north, throughout the Pacific Northwest (e.g. identical summer temps in northern Oregon). On the other hand, in San Diego, the water typically gets up to about 70F during late summer. Hilton Head in South Carolina is at about the same latitude, and water temperatures get quite a bit higher - 83F (though in Charleston, we were frequently getting 85-88F in July/August). The minimum temperatures on the "temperate" Atlantic coast are also a striking point of comparison - the minimum temperatures are the same as the maximum on the Pacific coast. There's much less seasonal variation here - maybe +/- 10F, whereas the gulf stream exerts a +/- 20-30F swing. The eastern North Pacific is cold and stable and the western North Atlantic is hot and unstable.

This is a long way of saying that there is a marked jump in marine climate from central to southern California. In addition to this, ambient air temperature is much, much warmer. The water in the tidepools gets warm real fast. As a result, it's very difficult to find nudibranchs during the day - don't even bother with small tidepools. I've seen a couple of tiny salt-and-pepper dorids in a tidepool in the mid-intertidal zone, where the water was about 5-10 degrees warmer. Nudibranchs do not tolerate wild temperature swings, nor do they like sunlight. Down here in socal, your best luck is going to be in tidepools down in the lower intertidal zone, or better yet, subtidal pools and channels at minus tides.

Nudibranch hunters under the winter stars. Well, planets - I believe those are Venus and Jupiter just after sunset.

That brings me to another major difference. The tides down here suck. They tend to be 1-2 hours earlier than in northern CA - primarily a result of the latitude. The tide variation is pretty similar to the bay area - highs around 6-7 feet, lows around 0-2 feet, with minus tides maxing out at about minus 1.7 on new moons. Our minus tides up north get a little lower, down to about minus 2 - but, pretty comparable. The timing is what is awful, though - at least for me. From April to September, minus tides are typically from 4-7am. If you're a morning person, I am jealous. If I get up after only 4-5 hours sleep and go tidepooling, I'll get a migraine even if I go take a nap (it happened last week). We do get daylight minus tides, late in the afternoon or trailing into the late morning hours, from October to March.

Collage of various socal tidepooling spots.

Northern and Southern California are also starkly different in terms of coastal access and beaches. Nine times out of ten your prospective tidepooling spot will be a state park, a popular beach, or a surf break. I have rarely had to fight hard for parking in Northern California (with one exception: Pillar Point/Mavericks on the annual winter solstice tidepooling event put on by California Academy of Sciences, but that's admittedly different). In socal, virtually ALL of the tidepooling spots will be below a residential neighborhood - and a very rich one at that. If you're from socal or lived here long enough, you probably won't mind having to walk a ways from your parking spot. On the same note, tidepooling down here has recently surged in popularity, and I've seen some distressing videos on social media of mobs of people flipping over every rock and throwing/hurting wildlife. I have tried to keep myself focused on some of the less popular tidepooling spots that are frequented by the real nerds, who try their utmost not to threaten the intertidal ecosystem and its denizens any more. I do flip rocks, on occasion - flat ones, only, and I try my best to gently place them back into position (I stepped on one last week that someone had flipped and got a huge bruise and some cuts on my knee when it rotated under my weight and clobbered me in the leg). And, owing to this recent surge in popularity, I will not divulge the location of any of my spots. I did a bit of research and trial and error to find these locations. If you have a similar 'doggedness' about you, you can earn it yourself.

Nearly flat-lying layers of marine sandstone of Cretaceous age exposed in San Diego County at a minus tide.

South of Point Conception, the rocks are almost completely sedimentary in origin. That means that there is very little in the way of leg-breaking craggy igneous and metamorphic rocks that tidepoolers from Big Sur, the Monterey Peninsula, or the Sonoma/Mendocino coasts might be used to. Those coastlines have locally chaotic topography owing to the bedrock - Salinian granite in Monterey, and Franciscan Complex metamorphic rocks in Big Sur and the coast north of Marin Co. The rocks down here are all typically deep marine sandstones and shales with nice bedding, with loads of concretions and surge channels formed along joints and fractures in the rock. There are some localities where the rocks are mostly large rounded cobbles, but they are few. You're more likely to slip by walking across nearly horizontal bedding planes covered in slippery algae than while climbing - though I've had pretty good luck down here so far. It also means that a little more walking might be required. Altogether, it's very similar to tidepooling on exposures of the Purisima Formation at Pillar Point and Fitzgerald Marine Preserve back at home up north. It also means that some of these sites are quite accessible for kids and adults with bad knees.

A California blue chromodorid (Felimare californiensis) cruising along in a cobble-filled tidepool.

One last word - nudibranchs in southern California also tend to be very small. On average, the nudibranchs I see are often half to 1/3 the size of members of the same species in Northern California. Large ones do exist, but they're usually spotted by divers or more ambitious tidepoolers who find them during 4am minus tides. Maybe I'm only finding the dumb babies during daylight minus tides. Nudibranchs are also less common. A good nudibranch day for me is finding more than two in one visit. Up in Northern California, for me, seeing less than thirty seems like a waste of a minus tide. Fifty is typical for a late afternoon minus tide, and I've seen over a hundred before on two or three minus tides.

The Big, Obvious, Easy to Find Nudibranchs

Depending upon the location, the Hopkin's Rose nudibranch, Okenia rosacea, is probably the most common and conspicuous nudi here in socal. They're not quite as common in Northern California. At some locations here, at a minus tide, you can spot several in the same visit. This species has also been placed in the genus Ceratodoris; it grows to a total of 3 cm. It inhabits the coast from Oregon to northern Baja and feeds on bryozoans.

Another Hopkin's rose. These nudibranchs get to about 4 cm and are most easily spotted when they're among kelp or seagrasses. They can easily blend in with the copious feather-like coralline algae in our tidepools.

An unusually large opalescent nudibranch, Hermissenda opalescens, at about 2 cm long. I've not seen a large one down here - they get to about 4-5 cm in northern CA. Most I have seen are around 1 cm in length - little babies. These are my favorite to find owing to the electric blue contrasting with the fiery looking cerata. This species can be distinguished from the 'horned' nudibranch, Hermissenda crassicornis, by having light tips on the cerata and lacking a longitudinal light stripe on each of the cerata. This species gets up to 9 cm, feeds on hydroids, and lives from northern California to southern Baja; H. crassicornis lives from northern California to Alaska. A third species, Hermissenda emurai, lives in Japan and the Korean peninsula.

We have two species of orangetip sea slugs, the genus Limacia - they are challenging to tell apart. MacDonald's dorid, Limacia macdonaldi, is more common in southern California, and Cockerell's dorid, Limacia cockerelli, is more common up North - though both live here. This one seems to have a row of orange tubercles on the back, and therefore is L. macdonaldi. This species was only named in 2017! It probably feeds on bryozoans like L. cockerelli. This species lives from Sonoma County, CA, to northern Baja.

The San Diego dorid (Diaulula sandiegensis), which is a cream-colored relative of the sea lemons. These are not terribly common - I find them in northern California more frequently - and the ones I see down here tend to be smaller. Subtidal specimens can get to 15 cm. They are identifiable based on a having a few dark ringed spots roughly arranged in two rows. The leopard dorid, Diaulula odonaghuei, is the sister species, and lives mostly from Mendocino County and north. This dorid mostly feeds on encrusting sponges.

A yellow-gilled sea goddess, Doriopsilla gemela. These are frequently encountered when flipping rocks over - and is how I found this one. These can get to 7 cm, and along with the white-spotted sea goddess below, are the most common "sea lemon" in southernmost California. These live from British Columbia to Baja California Sur and feed on sponges. These are one of the few nudibranchs that lack a radula. Instead, they release digestive fluid that partially digests the sponge which they suck up. Yum!

A white spotted sea goddess nudibranch, Doriopsilla albopunctata; these can be much darker in color, like this one resembling a roasted marshmallow, in southern California.

Somewhat Less Common, Absurdly Colorful Nudibranchs

The wildly blue-colored California blue chromodorid, Felimare californiensis - one of my absolute favorites. These don't even bother to camouflage themselves, so if they're out - you WILL see them! In this photo lies a tip to finding them: it's having lunch. Chromodorids eat sponges, and our three local chromodorids (California, Porter's and MacFarland's) all eat our yellow and orange encrusting sponges that live down in the subtidal zone. This species lives from Monterey Bay, CA, to southern Baja California Sur (La Paz, specifically).

A California blue chromodorid crawls past an onimous looking maw in the pool below - not anything to fear, it's just the exposed siphon of a rock-boring clam - specifically, a scale-sided piddock, Parapholas californica.

Macro portrait showing off exceptional detail of the rhinophores on the head of a California blue chromodorid (Felimare californiensis).

"Heeeeere's Johnny!" A california blue chromodorid squeezes between some strands of sargassum.

My absolute favorite southern California nudibranch - the incredible MacFarland's chromodorid, Felimida macfarlandi. Ecologically speaking they are similar to the California blue chromodorid and also feed on sponges. I've found them by flipping rocks as well as looking for zones of encrusting sponges during minus tides. This species lives from Monterey Bay, CA, to northern Baja California Sur.

A rather plump MacFarland's chromodorid (Felimida macfarlandi) I found under a rock.

One last view of a MacFarland's chromodorid working its way through brownish algae.

That's not candy corn - that's a Festive Babakina, Babakina festiva - one of our most flamboyant nudibranchs from the California coast. This individual was about 2 cm long. I have only seen two: this one, and a rather bleached looking individual a few months later. This species lives from Marin County, CA, to central Mexico.

Another shot showing the whole body of Babakina festiva, and all of its candy corn-like cerata. These are thought to feed on hydroids, like other aeolids - but little data is available.

A closer look at the head end and the comically inflated rhinophores of Babakina festiva.

Southern California's most outrageous, and probably most famous, nudibranch - the Spanish Shawl nudibranch, Flabellinopsis iodinea. These make my favorite nudibranch - the opalescent nudibranch - seem rather conservative in comparison. These can apparently get to massive sizes of 70 mm. These consume hydroids and steal the stinging cells and store them in their cerata.

Tiny, Hard to Find Nudibranchs

When I photographed this little guy - maybe 6 mm long - in October 2024, this species hadn't even been named yet; for the longest time, it was simply known as "Doto sp. A", and closely resembles the hammerhead Doto, Doto amyra. It was just named about one year ago, as Doto urak. Like other Doto spp., this one feeds on hydroids.

Another shot of this little cutie. Species in the genus Doto live worldwide, and their taxonomy has been quite challenging because they are typically under 1 cm in length.

A rather unusual find - this is a Pacific corambe (Corambe pacificus), I think - it could also possibly be a Steinberg's Corambe. These are relatively small, typically about 1 cm long, flattened, oval, and lacy - they look nearly identical to encrusting bryozoans that live on kelp fronds. Most folks have luck searching bryozoans on kelp to find these - I've only found them when I could tell there was a white blob on some sort of greenish algae.

Another Corambe - this one is next to a teeny little snail. I've spent plenty of time looking for these on bryozoan-encrusted kelp fronds, but had no such luck.

A tiny, ~6-7mm long white-crusted aeolid, Tenellia albocrusta. These are tiny, cryptic little nudibranchs that are hard to find but not uncommon. They live from Alaska to Baja and feed on hydroids.

Here's another Doto - the seal Doto, Doto kya. I've only ever seen one of these - this one was in Laguna Beach. They're the only California Doto with dark pigmentation on them. This species feeds on hydroids.

A branched dendronotid, Dendronotus venustus. These are apparently more common than I've encountered - another specimen from Laguna Beach. If it wasn't obvious by now, most of my luck finding cryptic, tiny nudibranchs is by searching amongst the red algae - very few of our nudibranchs blend in with red algae, and so virtually everything stands out. This species feeds on hydroids.

A salt and pepper dorid, Aegires albopunctatus. These are actually quite common, but most of them are about 8-12 mm in total length, and can look like a little bit of dead, bleached algae so it takes a bit of an eye to find them like these other more cryptic and rare forms. This species feeds only on calcareous sponges.

Ancula pacifica - no common name. These little ones look similar to species of Polycera (see below) but are pale and clear, with a few orange spots and stripes. Most are under 1 cm, but they get to 2 cm in length. This species feeds only on 'entoprocts', hydroid-like sessile filter feeders that are in their own phylum.

Curiously, this species may actually be a junior synonym of the eastern North Atlantic form Ancula gibbosa - suggesting that there may be one worldwide, or at least northern hemisphere, population of this tiny nudibranch. It seems unlikely to me - and, there are some anatomical differences.

Baby Nudibranchs

By virtue of having a search image tailored for tiny nudibranchs, I seem to come across babies of large species much more frequently down here. Some of these can pose a challenge to identify, thanks to occasionally looking quite a bit different than the adults - sometimes more pale, other times more vividly colored - and often with fewer cerata.

A juvenile San Diego dorid, Diaulula sandiegensis - this one was about 1 cm long, and was difficult at first to ID until I realized that it's a juvenile San Diego dorid without any spots. It looks suspiciously like a ridge tailed dorid, but the rhinophores look totally different. Fortunately, there are a few examples of juveniles posted to iNaturalist that helped me out.

A tiny, ~8mm long juvenile colorful dirona - Dirona picta. Examples of this species can get up to 10 cm, though most intertidal individuals are under 3 cm; this is the smaller, less spectacular relative of the white-lined Dirona (Dirona albolineata) that inhabits the Pacific Northwest. It feeds on bryozoans and hydroids and lives from northern Oregon to Baja.

Technically my first sorcerer's dorid find (Polycera atra) - though I didn't realize it until I got home and processed this photo of a Norris' top snail (Norrisia norrisi) sporting a spectacular growth of coralline algae.

A baby sorceror's dorid, Polycera atra. These handsome little fellows are commonly found further north during dockfouling - I've seen a couple of babies in the tidepools down here. These get to about 2 cm long and feeds on one particular type of bryozoan.

A juvenile opalescent nudibranch, Hermissenda opalescens, perhaps 15 mm long.

A juvenile (~12-15 mm) cockscomb nudibranch, aka Santa Barbara janolus, Antiopella barbarensis. These feed on bryozoans and get to xxx cm, and live from San Francisco to Baja; they feed only on bryozoans.

Another juvenile cockscomb nudibranch,Antiopella barbarensis.

A juvenile Fisher's aeolid, Orienthella piunca, about 1 cm long. There's not much data on this species - it is easily mistaken for the three-lined aeolid (O. trilineata), which does not frequently have orange rhinophores. Identifying these socal aeolids with reddish cerata can be challenging!

Another Fisher's aeolid (O. piunca) but this one doesn't have a median white stripe like most of the individuals photographed online have!

A juvenile, ~1 cm long MacFarland's dorid, Limacia macfarlandi.

Other sea slugs - Saccoglossans, Aplysiomorphs, and Cephalaspideans

A baby Navanax inermis - the California aglaja. Juveniles under 10 cm in length are most commonly seen in tidepools, and bigger ones can be seen subtidally. This species ranges from Marin County to central Mexico.

Navanax is a genus of 'headshield slugs' (Cephalaspidea) that are closely related to the sea hares. Some of these, like bubble snails, still have a reduced shell. Navanax grow to 25 cm and their yellow spots transition to more numerous and fine yellow lines; as adults they have more yellow/white on them than black. They are voracious predators of nudibranchs - so if you see one, you're on the right track! These are much easier to spot than nudibranchs as they are a little more tolerant of warmer water and sunlight.

A monstrous Navanax in about a meter of water in Mission Bay, seen while snorkeling. This one was about 20 cm long - still not full grown!

A white bubble snail, Haminoea vesicula - another species in the headshield slugs (Cephalaspidea) and one that, unlike Navanax, is an herbivore. These tend to feed on green algae like sea lettuce (Ulva). Bubble snails are usually tropical in distribution, and this species ranges from southern Alaska to Baja California Sur; it gets to about 4 cm long.

A teeny, tiny baby California sea hare, Aplysia californica. This one was only about 3 cm long, and reddish - it blended in with the red algae really well. This species lives from the central Oregon coast to El Salvador - quite a range! It's also been reported in Japan.

The California sea hare, Aplysia californica, is probably the most abundant sea hare, but perhaps a little less commonly spotted owing to their much smaller size than the black sea hare. These are most commonly about 15-25 cm in length, but can grow to an incredible 70 cm; the largest I've seen was about 35 cm, stretched out (the individual photographed here). These are tan to brown with spots and ruffled edges of its 'flaps'. These are herbivores and feed mostly on red algae. They can produce dark purple ink if disturbed - just like an octopus! Further, this ink is also quite toxic - which helps explain how these giant mollusks can graze about the tidepools without a worry.

The gigantic sea slug of southern California, the black sea hare, Aplysia vaccaria. These are much larger, with a maximum body length of around one meter - outstretched, I assume; most that I have seen while plump are around 50-60 cm. They can also weigh quite a lot - up to 30 pounds (~14 kg) - making them the world's largest gastropod! These are always jet black, and have smooth edges to their 'flaps'. This species mostly feeds on feather boa kelp and other similar fleshy green algae.

A black sea hare (Aplysia vaccaria) feeding on sargassum. These guys don't produce ink like their smaller brown relatives. A phenolic compound in brown algae that helps safeguard against kelps from being eaten, acetoxycrenulide, is accumulated in the tissues of this species. Kelps have a number of phenolic compounds that are toxic to herbivores - yet this species not only developed a tolerance to it, but co-opted it for its own defense.

A black sea hare (Aplysia vaccaria) laying a massive spaghetti-like mass of eggs. Sadly, this sea hare is at the end of its lifespan - they grow very quickly, 5 grams per day, and mate and reproduce at at the end of one year. This species lives from Monterey Bay to the Sea of Cortez.

Sapsuckers are members of the Sacoglossa - and while these can look very similar to sea hares, even having a pair of flaps down the back, they are not even in the Euopisthobranchia - they are more closely related to pulmonate land snails. This is Hedgpeth's sapsucker, Elysia hedgpethi. These feed on green algae and store the chloroplasts in their tissues. I find these by looking over "Dead man's fingers" algae (Codium) and looking for little green blobs. These get to about 2-5 cm long, though most that I find are under 1 cm. They have beautiful little reflective star-like spots on them. The better known 'sea lettuce' slug from the Caribbean is also in the genus Elysia.This species of Elysia lives from Vancouver Island to Puerto Vallarta in Mexico.

While some sapsuckers are superficially similar to sea hares, others look very similar to nudibranchs. This is the branched sapsucker, Placida dendritica. These are tiny, and rarely exceed 1 cm. These feed on green algae and, like Elysia, can most easily be found on bits of the algae Codium (dead mans fingers). This species may live worldwide in temperate waters.

Critters That Look Like they Should Be Nudibranchs But Aren't

This is one of several flatworms that live in southern California tidepools - and the one I've seen the most. This is the aptly named dalmatian polyclad, Enchiridium punctatum. They live on the coast from Los Angeles, CA, south to the Sea of Cortez. I have found several underneath rocks, and occasionally out in the open like this one (my first sighting). I can't find much about its diet.

An unusual sighting: an umbrella snail, Tylodina fungina. These look like a cross between a limpet and a nudibranch, but they are neither. They are sometimes called false limpets, and are closely related to the headshield slugs (Cephalaspidea) and the aplysiomorphs (sea hares) as well as the pteropods ('sea angels'). All of these groups have a highly reduced shell; these are the least 'sluggy' of them.

Another Tylodina fungina. Every time I see these I expect it to be a sea lemon. Virtually all sightings of these are south of Ventura County. These gastropods mostly feed on the yellow suphur sponge, Aplysina fistularis.

Further Reading

Kelly, R.P., T. Klinger, P.J. Krug, and J.J. Meyer. 2024. Between the tides in California: exploring beaches and tidepools. University of Washington Press. 312 pp.

Ricketts, E.F., and J. Calvin. 1965. Between Pacific Tides. Stanford University Press. 502 pp.

Sept, J.D. 2023. The new beachcomber's guide to seashore life of California. Harbour Publishing. 432 pp.

The fossil record of early cetaceans from New Zealand, 3: toothed whales (Odontoceti)

2026-05-11T03:00:00.000-07:00

For archaeocete whales, toothed baleen whales, and a review of the mid-Cenozoic stratigraphy of New Zealand, see part 1. For baleen-bearing baleen whales, see part 2.

Ewan Fordyce posing with a cast of the skull of the early dolphin Waipatia maerewhenua from the oligocene Otekaike Limestone of New Zealand.

Baleen whales are arguably more common in the Oligocene of New Zealand than anywhere else on the planet - as detailed in the previous entry, at least half of the world's chaeomysticetes - but it is probably more famous for its fossil dolphins, which were Ewan Fordyce's true passion. Now, I am going to cheat a little bit, and include some early Miocene fossils here as they are of similar evolutionary grade and quite central to the story of dolphin paleontology down under.

A collection of fossil and modern odontocetes out on the Otago Geology Museum table, actual specimens and casts, from left to right: Squalodelphis fabianii (cast), Otekaikea marplesi (original), Waipatia maerewhenua (cast, light yellow, in back), Otekaikea huata (original, foreground), and Tursiops truncatus (modern skull).

There were numerous isolated finds made quite early on consisting of partial teeth, or sets of associated teeth in jaw fragments - early discoveries were made in the late 19th century when collecting methods were not yet refined, certain fossils consisted of teeth plucked out of outcrops or skull chunks recovered during quarrying. If I remember right, Ewan described the first 'modern' excavation of a fossil cetacean in New Zealand with anything resembling a plaster jacket to have been the Tokarahia lophocephalus excavation by Brian J. Marples in 1942.

Some of the teeth in blocks of limestone from Milburn and Clarendon quarries in central Otago, from Benham (1938), originally assigned to Lophocephalus parki, and then later named Squalodon andrewi.

"Squalodon" andrewi is one of the oldest named odontocetes from New Zealand, and like the naming of the genus Mauicetus, it stemmed from the misidentification of a chimaeric association of fossils by Benham (1937) when he named Lophocephalus parki as an archaeocete. If you recall from part 1, after some correspondence with Remington Kellogg, Benham came to accept that the holotype braincase fragment was from a Parietobalaena-like mysticete. He renamed Mauicetus parki, given that the genus name Lophocephalus was preoccupied by a beetle. He had, however, also assigned some teeth to "Lophocephalus", but now realized they were not from Mauicetus parki. He designated these as Squalodon andrewi - although none of the specimens likely actually represent Squalodon, which has been badly mistreated as a wastebasket taxon. "Squalodon" andrewi consisted of three tooth-bearing jaw fragments in limestone blocks, all that was salvaged from squalodontid skulls or mandibles from the Milburn Limestone of South Otago in the vicinity of Clarendon, just a few km northeast of Milburn. The holotype is a single tooth with double roots, and the remaining specimens appear to represent several different odontocetes. Not much further can be said about "Squalodon" andrewi. Ewan excavated a beautiful skull of a squalodontid from Milburn Quarry, the "Milburn" squalodontid, with rather similar teeth to one of Benham's (1937) specimens. All of the Milburn/Clarendon material share relatively highly rugose enamel in comparison to true Miocene Squalodon from the North Atlantic.

Cast of the skull and mandible of the Earthquakes squalodontid. Photo by Morgan Churchill.

Perhaps the most famous image of the Earthquakes squalodontid, with preparator Andrew Grebneff examining the teeth. This photo no longer appears online in full resolution. Photo by Ewan Fordyce.

The excavation pit from the site where the Earthquakes squalodontid was excavated in the late 1980s, on a field trip to the Earthquakes with Ewan in summer (NZ winter) 2013. From left to right: Morgan Churchill, Cheng-Hsiu Tsai, Josh Corrie, and Ewan Fordyce. The skull was collected from the base of this ~12 foot cliff, and they dug out a cone-shaped hole above it to keep the limestone from caving in. The hole itself is visible just to the right of Josh Corrie (blue shirt). Photos by me.

In the late 1980s, Ewan and colleagues excavated a rather large Squalodon-like skull from the Otekaike Limestone at the Earthquakes - this specimen has since been nicknamed the "Earthquakes squalodontid". Whether it's a true squalodontid or not is a different issue, but it is a rather large skull (nearly 1 m long) with a long, cylindrical rostrum, and a much greater degree of telescoping of the skull than Ankylorhiza. In many regards it is superficially similar to Phoberodon arctirostris, a Squalodon-like odontocete from the lower Miocene of Argentina. It pains me to write that this specimen has not yet been described, and was one of Ewan's unfinished legacy projects. He cared very deeply about the squalodontids, frequently joking that he might have time to work on them after retirement.

The lower Miocene Caversham Sandstone at Tunnel Beach, south of Dunedin. Photo by me.

The first truly significant fossil odontocete from the mid-Cenozoic of New Zealand did not originate from the Oligocene units but was collected from the Caversham Sandstone, earliest Miocene in age. The Caversham Sandstone forms incredibly scenic coastal cliffs south of Dunedin (which I have painted in watercolors and acrylic on canvas) as well as north of Dunedin in the cliffs near Waikouaiti. In 1902, Mr. Augustus Hamilton collected a block containing a large partial skull from Caversham Quarry in the southwestern part of town - Caversham is a neighborhood sandwiched between the coastal neighborhood of St. Clair (where we would occasionally go to the beach) and central Dunedin. I've no idea where the quarry is today, if any of it remains, but my fellow student Gabriel Aguirre-Fernandez - studying NZ fossil kentriodontid dolphins from this and other Miocene units - had identified at least one possible skull awaiting collection in a roadcut nearby, as well as another skull nearly 20 feet up the cliff at Tunnel Beach.

The holotype skull and one of the teeth of "Prosqualodon" hamiltoni, a Phoberodon-like squalodontid grade dolphin from the Caversham Sandstone (earliest Miocene).

Mr. Hamilton's skull was quite large - 34 cm wide, around the size of a pilot whale - and preserves a virtually complete braincase and the posterior third of the rostrum. There are a handful of teeth, with double-rooted teeth bearing longitudinal ridges on the enamel and some serrations. Professor Benham conservatively named this species Prosqualodon hamiltoni in a 1936 paper - referring it to the same genus as Prosqualodon australis named by Lydekker 50 years prior from the lower Miocene of Patagonia, and the more recently named Prosqualodon davidis from lowermost Miocene rocks of Tasmania across the Tasman. Benham was well-aware of the differences between the New Zealand skull and fossils of P. davidis and P. australis, including the dentition: he clearly noted how the teeth were simpler than those of P. davidis and P. australis, which have more rugose enamel with "reticulated ridges", and he also pointed out that true Prosqualodon spp. have accessory cusps but that these are absent in P. hamiltoni.

Recently published photos of the holotype skull of "Prosqualodon" hamiltoni from Gaetan et al. (2025) - highlighting the many differences in the skull between it and Prosqualodon australis.

Benham did not provide much of a description of the skull, but the following observations can be summarized in a modern context. It has a rounded occipital shield and a wide vertex, with a small rectangular 'table' between the occipital bone and the nasals - roughly similar to Squalodon, Waipatia (see below), and many dolphins on the odontocete stem as well as some early crown odontocetes. The vertex is positioned anteriorly as are the orbits, and the temporal fossae - the spaces for the jaw-closing temporalis muscles - are cavernous, and visible in dorsal view. The premaxillae are relatively wide, and so is the mesorostral groove - it is nearly rectangular in outline. The sum of these observations indicates to me that P. hamiltoni is something similar to Ankylorhiza from South Carolina, but very likely something more 'primitive' than Phoberodon, Squalodon, or Prosqualodon. In particular, P. hamiltoni really looks like "Genus Y" - the undescribed species of Ankylorhiza represented by ChM PV 2764 at the Charleston Museum, right down to the teeth. Ewan considered it to be a squalodontid in his 1994 paper on Waipatia, and it decidedly does not closely resemble Prosqualodon davidis or P. australis - especially in lacking the short rostrum that is unique to true species of Prosqualodon. Little had been written on this specimen in the past 90 years, until Maximilian Gaetan and colleagues (2025) published a new paper on Prosqualodon australis. They coded P. hamiltoni into a phylogenetic matrix for the first time, and unsurprisingly this taxon plotted out amongst the waipatiids, specifically in a weakly supported clade formed with the much, much smaller Nihohae and Nihoroa. However, the analysis included only Ankylorhiza tiedemani, which lacks earbone codings - and it's likely that these relationships might change pending inclusion of more complete specimens like Ankylorhiza sp., ChM PV 2764, which has been coded in many previous analyses. Regardless, this is pretty solid evidence that "Prosqualodon" hamiltoni is something else and not related to Prosqualodon australis. If it IS a giant waipatiid and not something like a squalodontid (which I strongly doubt) or something close to Ankylorhiza, it would imply repeated evolution of large bodied odontocetes in the southern Ocean (at least 3-4 lineages including "P." hamiltoni, the Earthquakes and Milburn squalodontids, and of course Prosqualodon itself).

The teeth of Tangaroasaurus kakanuiensis, another Phoberodon-like squalodontid dolphin from the lower Miocene - probably collected from the Gee Greensand. From Benham (1935), who initially identified this as an ichthyosaur.

In 1935, Benham reported an isolated tooth of a large dolphin from near Kakanui and named it Tangaroasaurus kakanuiensis, incorrectly assuming at the time that the specimen represented a marine reptile, and specifically an ichthyosaur. Curiously, one of these specimens is quite clearly a double-rooted tooth that's been broken down the middle. Further curious is that earlier reports indicated that the specimen was Miocene and associated with fossil whale remains - acknowledged by Benham. In his review of California mosasaurs, Camp (1942) cited communications with Remington Kellogg who considered the fossil to be a squalodontid; Brian Marples (1949) and Ewan Fordyce later agreed with squalodontid affinities. Mandible fragments illustrated by Benham (1935) are now lost. In 2013, Ewan took us on a field trip to the exact spot where it was collected, an exposure of the lower Miocene Gee Greensand. Ewan suggested, in conversation to me on a couple of field trips, that it perhaps was synonymous with Phoberodon from coeval rocks in Argentina.

The holotype mandible and teeth of "Microcetus" hectori, named by Benham (1936) - later recombined as Waipatia hectori by Tanaka and Fordyce (2016). From Tanaka and Fordyce (2016).

The skull of Waipatia hectori, which was sitting in a block of limestone at the Te Papa Tongarewa National Museum of New Zealand for nearly a century, discovered in collections by Ewan and linked with Alexander McKay's notes to the mandible originally published by Benham. From Tanaka and Fordyce (2016).

The teeth of Waipatia hectori. Some of these were known to Benham, others were embedded in matrix still. From Tanaka and Fordyce (2016).

Another specimen, and the last named by Professor Benham, was named Microcetus hectori in 1936. Microcetus ambiguus is a set of associated teeth from the Oligocene of Germany, named earlier. At the time, the referral seemed reasonable. Microcetus hectori was chiefly named based on a small mandible (misidentified by Benham as a maxilla; it is admittedly crushed into a triangular shape, resembling a maxilla) fragment with five well-preserved teeth in it, along with parts of eight additional teeth, all collected from the Otekaike Limestone somewhere in the Waitaki Valley (the original precise locality has been lost) - but is known to have been collected by early NZ geologist Alexander McKay in summer of 1881, making this one of the oldest fossil cetacean discoveries in the country. The mandible itself is quite cute - I've held it - and it's got these tiny little teeth in it that are quite distinctive: they have a ridge with zig-zag shaped 'crenulations' on the lingual (tongue) side of the teeth - called a cingulum - and a poorly developed labial (lip side) cingulum that consists of a few vertical ridges; the teeth are otherwise smooth closer to the crown. The teeth are quite tall, lack mesial (anterior) accessory cusps, and have only two distal (posterior) accessory cusps. Later study by Ewan Fordyce during his doctoral program revealed unprepared blocks of limestone collected along with the mandible fragment reported by Benham, hiding in the collections of the national museum (Te Papa). Among these blocks was quite a bit of a braincase, which was then prepared further by Yoshi Tanaka during his Ph.D. (Yoshi was my office mate, and so I had a front seat to much of the research covered in this post!). The skull revealed a number of close similarities with Waipatia maerewhenua (see below), leading Tanaka and Fordyce (2016) to reassign the species to Waipatia as Waipatia hectori.

The original illustration of "Prosqualodon" marplesi, from Dickson (1964) - it's got all the hallmark features illustrated. Later named as the new genus Otekaikea by Tanaka and Fordyce (2014).

The holotype skull of Otekaikea marplesi in dorsal view, from Tanaka and Fordyce (2014).

Reconstruction of the skull, mandible, and dentition of Otekaikea marplesi, based on then as-yet-unnamed Otekaikea huata and Waipatia maerewhenua. From Tanaka and Fordyce (2014).

The earbones (periotic and tympanic bulla) of Otekaikea marplesi. From Tanaka and Fordyce (2014).

Yoshi Tanaka doing some preparation of the bulla of Otekaikea marplesi in spring 2013.

Otago Geology Master's student M.R. Dickson (who I met in 2014 or so) continued the trend of assigning fossil dolphins to Prosqualodon when he named Prosqualodon marplesi from the "Trig Z" locality in the Otekaike Limestone near Duntroon. This specimen consists of a well-preserved braincase lacking the rostrum, but preserving a partial mandible, atlas and axis vertebrae, a beautiful scapula, and other postcrania. The skull is superficially similar to Squalodon in its general morphology: there is no intertemporal constriction, meaning the skull is quite telescoped. The posterior end of each premaxilla is split into a swallowtail shape - called the premaxillary cleft by later workers. The vertex is formed by the frontal and nasals, and is table-shaped and somewhat squared; the nasals are small and rectangular. Superficially similar to some platanistoid dolphins like the Squalodelphinidae, the 'postglenoid process' - part of the squamosal bone that forms the skull half of the jaw joint - tapers ventrally, rather than having a rectangular shape as in Waipatia (see below). The periotic bone is generally similar to Squalodon in certain features (moreso than to squalodelphinids). Later, this species was reassigned to Notocetus by Fordyce (1994), and then eventually recognized as a waipatiid dolphin (see below) and named its own genus as Otekaikea marplesi by Tanaka and Fordyce (2014).

The holotype skull and mandible of Waipatia maerewhenua, from Fordyce (1994).

More images of the skull of Waipatia maerewhenua, along with the tympanic bulla. From Fordyce (1994).

In 1989, Ewan was prospecting with preparator Andrew Grebneff and came across the tip of a small cetacean snout sticking out of the Otekaike Limestone in the vicinity of Waipati, on Mike Harvey's farm (this was, by the way, very close to the type localities of the later-described mysticetes Tohoraata raekohao and Whakakai wapaiti described by C-H Tsai and yours truly). They excavated the specimen, and brought it back to the Otago lab. The skull resembled shark-toothed dolphins in some ways, but had relatively small teeth, and was much smaller - and older - than any species of Squalodon. Ewan set about writing the specimen up, eventually published in the Proceedings of the San Diego Society of Natural History, in a special volume honoring Smithsonian paleontologist Frank Whitmore. He named it Waipatia maerewhenua - after the locality, Waipati, and the nearest river, the Maerewhenua river. This was the first of many New Zealand fossil cetaceans named in the Maori language - and while most American speakers I've heard have little trouble pronouncing the genus, I'm highly, deeply, genuinely amused every time someone tries to pronounce the species name around me, knowing I know how to do it, saying "mar-uh... uh..." and trailing off into an intentionally quiet noncomittal utterance as. I always let folks try and pronounce it on their own before offering the correct version. For a brief guide to Maori pronunciation, check out the first post in this series.

The teeth of Waipatia maerewhenua, from Fordyce (1994).

Waipatia is a very interesting dolphin, and it is clearly the same evolutionary grade as "Prosqualodon" marplesi, "Microcetus" hectori (which, as discussed above, was recombined as Waipatia hectori more recently). Most critically, Ewan Fordyce recognized that this was the first well-preserved early odontocete from the Oligocene that had a nearly complete skull, well-preserved earbones removed from the skull, nearly complete mandible, and most of the dentition. In this regard, it's a keystone specimen for the study of early odontocetes. Further, and perhaps more critically, the anatomy of Waipatia is quite revealing - first, it clearly indicated that a whole new family, the Waipatiidae, needed to be named in order to contain it. Waipatia is similar in its overall grade of evolution to Squalodon, and even has some similar earbone features, but is much smaller, with smaller teeth. Like Squalodon, it has some tusk-like incisors, double-rooted teeth, heterodonty (the teeth dramatically change shape from front to back), polydonty (more than 11 teeth per quadrant, the primitive number for placental mammals). The earbones had some features that Fordyce considered grouping Waipatia with platanistoids* (a controversial group altogether). These include a spine on the anterior end of the tympanic bulla, and a little ridge on the posterolateral side of the periotic called the articular process. In modern toothed whales, this process is only observed in Platanista gangetica, the Ganges River dolphin**. Ewan conducted the first computer-run cladistic analysis of odontocete relationships (and quite possibly of cetaceans in general) and did recover Waipatia within the Platanistoidea.

*There are two historical concepts of the Platanistoidea: 1) the Platanistoidea of G.G. Simpson, in which the group is formed only by modern river dolphins - this has been widely discounted for about 30 years now as none of these dolphins are related to each other; 2) the Platanistoidea of C. de Muizon, including the modern species Platanista and everything more closely related to it. This has in the past included the Waipatiidae, Squalodontidae, Allodelphinidae, and the Squalodelphinidae; it seems however that the waipatiids and squalodontids likely do not fall inside the odontocete crown group, or within this more modern concept of the Platanistoidea.

**Over the years, many other early odontocetes have been found with the articular process, and having one seems to have been the primitive condition for Odontoceti, rather than indicating platanistoid relationships. Honestly, I could do an entire blog post about the Platanistoidea.

Other possible waipatiid dolphins - from Fordyce (1994).

Yoshi Tanaka in our office holding a cast of the skull of Waipatia maerewhenua. The holotype braincase of Otekaikea marplesi is behind him to the left, and the rostrum of a modern Tursiops is at the lower right. Photo by me. As you can tell from the window, we were both in the office way too late.

The discovery of Waipatia had some further implications for dolphin evolution. The skull shows some evidence of cranial asymmetry - it's subtle, but there are some features worth noting: 1) the base of the rostrum has a flared crest on the right maxilla, 2) the left premaxilla extends further posterior than the right; 3) the nasals and nasofrontal suture are rotated in dorsal view so that the right nasal is shifted further anterior; and 4) the exact positions of some of the foramina in the facial region are not precisely symmetrical, in number or configuration. Altogether, this is suggestive of asymmetrical facial muscles involved in echolocation. Further evidence that Fordyce (1994) outlined includes the presence of premaxillary sac fossae, which are present throughout modern toothed whales (all of which can echolocate); these structures house the muscles that retract the nasal plugs, which seal off the nasal passages during diving and may have a role in sound generation. Though not outlined clearly by Fordyce, Waipatia has a concave facial plane, widely considered a bony correlate of the melon in cetaceans - a soft tissue structure intimately linked with echolocation. Ewan also concluded that several other odontocetes were candidates for inclusion in the Waipatiidae, given that these species are smaller than Squalodon and of similar Oligocene age. The first is of course Microcetus ambiguus from the Oligocene of Austria, to which Benham (1935) originally referred Microcetus hectori. The teeth are roughly similar, but suggest confamilial rather than congeneric affinities. Microcetus sharkovi is a small Waipatia-like dolphin reported from Oligocene rocks of Kazakhstan by Georgian paleocetologist Guram Mchedlidze (isolated from the west within the Soviet Union during the entirety of his career), and it has small heterodont teeth, unlike Squalodon. Another small beast named by Mchedlidze is Sulakocetus dagestanicus from the Caucasus Peninsula, similarly having small heterodont teeth and small size like Waipatia (and differing from squalodontids), and very likely belongs in this group. The last is another waipatiid behind the iron curtain, Sachalinocetus cholmicus, named by Irina Dubrovo from Sakhalin Island (between Japan and the Kamchatka Peninsula) - also from the western Pacific, but from lowermost Miocene deposits. Sachalinocetus has a much more elevated skull, resembling Ediscetus from South Carolina.

Ewan Fordyce posing wiht the beautifully preserved holotype skull of Papahu taitapu. Photo by Ewan Fordyce (not kidding: he did these with a remote shutter release).

The holotype skull of Papahu taitapu in dorsal view, from Aguirre-Fernandez and Fordyce (2014).

The holotype skull of Papahu taitapu in ventral view, from Aguirre-Fernandez and Fordyce (2014).

The holotype skull (and mandible) of Papahu taitapu in anterior and lateral view, from Aguirre-Fernandez and Fordyce (2014).

The holotype periotic of Papahu taitapu, from Aguirre-Fernandez and Fordyce (2014).

A little skull that Ewan and preparator Andrew Grebneff collected in 1987 from the lowermost Miocene Kaipuke Siltstone at the north end of the South Island was the subject of one of the major chapters in Gabriel Aguirre-Fernandez's Ph.D. thesis, and he got it published in 2014 (Aguirre-Fernandez and Fordyce, 2014). This little skull was initially thought to be one of the world's oldest known delphinoids, and a possible kentriodontid - however, careful study and revised codings during his Ph.D. revealed that it's actually a stem odontocete, and similar in many regards to waipatiid-grade dolphins. The skull was named Papahu taitapu, Maori for dolphin and 'northwest coast' (Te Tai Tapu). The skull is rather small, only 18 cm wide, and the entire specimen as preserved is only 32 cm long, and was probably around 37-40 cm long when complete - it's missing just the tip of the rostrum. In general, however, it doesn't really closely resemble kentriodontids; the vertex is quite primitive looking with a large flat table of the frontal exposed, like Waipatia, and the posterior end of the premaxilla is split with a cleft and two plates - just like Waipatia and Otekaikea spp. (see below). However, perhaps critical to the initial misattribution, was the fact that the tooth sockets all appear to be single-rooted.* One feature that was critically lacking that resulted in the recognition of this specimen as being clearly outside the Delphinioidea (and therefore Kentriodontidae as well) was the lack of an infraorbital extension of the pterygoid sinus fossa - this is a bony trench or fissure that connects with the pterygoid sinus fossa just in front of the earbones, and houses air and blood-filled sinuses that serve to both help acoustically isolate the earbones during underwater hearing and function as venous drainage during diving. It's pretty complicated, so I'll leave it at that for now - the key takeaway is that this fossa/sinus system is restricted to the auditory region in Papahu, just like Waipatia and Squalodon. However, it does share a feature with Delphinida (a big clade in odontocetes that basically includes the Delphinoidea and a couple of South American river dolphins, along with many delphinoid-like fossils) - a lateral lamina of the palatine (though this is sporadically found in a couple of other stem odontocetes, like Prosqualodon davidis).

*However, it is possible that the teeth were in fact double rooted, but crowded, so no pairing of the alveoli is evident. It's a slim chance, but we won't really know until a specimen of Papahu with teeth is found. Given that many heterodont dolphins diverge after Papahu on virtually all cladistic analyses, it is not out of the question (and perhaps even likely, in my opinion).

Most of the Otago Lab at the time that Papahu taitapu was named by Gabriel Aguirre-Fernandez and Ewan. From left to right: Carolina Loch, Yoshi Tanaka, Gabriel, Felix Marx, yours truly, and of course, Ewan Fordyce. Photo courtesy Otago Daily Times.

The earbones of ZMT 73, a specimen identified as cf. Papahu, from Tanaka and Fordyce (2016).

Two years later, Yoshi published on a fragmentary specimen (Tanaka and Fordyce, 2016) that Ewan had studied in his thesis, ZMT 73, which they identified as cf. Papahu. Critically, this specimen had a more complete periotic and bulla, revealing some additional features not evident in the juvenile holotype specimen. Improved coding and sampling pulled both Papahu taxa from the stem Odontoceti (as in Aguirre-Fernandez and Fordyce, 2014) or the Platanistoidea (as in Tanaka and Fordyce, 2015) into a clade with the Ziphiidae (beaked whales), Eurhinodelphinidae ("swordfish dolphins"), and the Delphinida. At face value, there are many broad similarities with early Miocene dolphins like eurhinodelphinids, especially within the periotic. We need more studies of early Miocene odontocetes with crazy long snouts, and I wouldn't be surprised if Papahu fits in right there; its periotic looks like a swollen eurhino periotic, and as Tanaka and Fordyce (2016) point out, it has a very similar looking bulla to ziphiids and eurhinos.

The holotype skull and mandible of Otekaikea huata in lateral and dorsal view. From Tanaka and Fordyce (2015).

The holotype incisor tusks and other teeth of Otekaikea huata. From Tanaka and Fordyce (2015).

The holotype periotic (and bulla fragment) of Otekaikea huata. From Tanaka and Fordyce (2015).

The holotype mandible of Otekaikea huata. From Tanaka and Fordyce (2015).

The holotype right forelimb of Otekaikea huata, in lateral view. From Tanaka and Fordyce (2015).

After Tanaka and Fordyce (2014) redescribed "Prosqualodon" marplesi and named the new genus Otekaikea, they published a followup paper a year later (Tanaka and Fordyce, 2015), naming a more spectacularly preserved specimen from the Oteikaike Limestone at Hakataramea quarry as Otekaikea huata. Otekaikea huata has more of the rostrum preserved, along with more postcrania: a similar number of vertebrae, some ribs, a sternum, and a nearly complete forelimb including scapula, humerus, radius, and ulna. The rostrum is quite poorly preserved - none of the elements quite connect with each other and they are all highly bioeroded, but it was clear from the premaxillae that the rostrum was quite long, perhaps 2.5 times the length of the braincase. The skull is slightly wider than Waipatia - 26 v. 24 cm - but is quite a bit longer, nearly 80 cm, as opposed to ~60-65 cm for Waipatia. The incisor tusk is surprisingly large, being at least 20 cm long, 1.5 cm in diameter, and the crown has been completely worn away, perhaps down to the gumline; the estimated total length, including the crown, is 28 cm (!). The anteriormost tooth is not preserved in Waipatia, but it was likely not quite so large; in Otekaikea marplesi, the equivalent tooth is quite a bit smaller. The cheek teeth are somewhat more homodont than in Waipatia and have fewer denticles. The facial plane of the skull is more deeply concave, and the facial region in general is somewhat more asymmetrical than in Waipatia - this further suggests that Otekaikea (and waipatiids in general) was capable of echolocation. Tanaka and Fordyce (2014) ran a phylogenetic analysis of odontocetes, which was modified from a matrix by Mizuki Murakami focused on delphinoids; they added 16 characters from other studies, for a total of 278 characters coded for 76 modern and extinct species. In their analysis, they recovered a waipatiid clade including Waipatia and Otekaikea, along with OU 22125, which would later be named Awamokoa tokarahi (see below). This monophyletic Waipatiidae was found to be sister to the Squalodelphinidae and Platanistidae, and is one of the few recent studies to have found anything beyond platanistids and squalodelphinids recovered in this clade. In one of their two analyses, they also recovered squalodontids as platanistoids.

The holotype skull fragment and right periotic of Awamokoa tokarahi. From Tanaka and Fordyce (2016).

The holotype left mandible of Awamokoa tokarahi. From Tanaka and Fordyce (2016).

The holotype teeth of Awamokoa tokarahi. From Tanaka and Fordyce (2016).

A fragmentary skeleton from the Kokoamu Greensand at Awamoko Stream near Tokarahi was named Awamokoa tokarahi by Tanaka and Fordyce (2016). This species is the oldest named odontocete from New Zealand, and one of the only ones from the Kokoamu Greensand - it's slightly older than Waipatia, which is from low in the Otekaike Limestone. Awamokoa is known from the edge of the right side of the braincase, and includes a well-preserved auditory region of the skull along with the right periotic, both tympanic bullae, a partial left mandible, a handful of teeth, cervical and thoracic vertebrae, a partial forelimb, and ribs. Awamokoa is generally similar to Waipatia and Otekaikea in most regards, but has a long temporal fossa suggesting that it had a slower but more powerful bite than later "platanistoids", which had longer rostra and smaller teeth, suggestive of more rapid snapping. Though no tusks are known, there are some long-rooted anterior teeth consistent with having procumbent teeth up at the tips of the jaws.

The fragmentary skull of aff. Prosqualodon davidis from the Mt. Harris Formation of New Zealand with an outline of the holotype from Tasmania. From Tanaka et al. (2022).

The fragmentary skull of aff. Prosqualodon davidis from the Mt. Harris Formation of New Zealand. From Tanaka et al. (2022).

Teeth belonging to the New Zealand specimen of aff. Prosqualodon davidis. From Tanaka et al. (2022).

One of the only published specimens from the Mt. Harris Formation is a partial skull found in siltstone exposures in the wave-cut platform at Awamoa Beach in 2001, and featured prominently in former Otago student Megan Ortega's thesis. The specimen was finally published by Yoshi Tanaka, Megan Ortega, and Ewan in 2022, and identified as cf. Prosqualodon davidis - an extension of the range of this species from Australia to New Zealand. The skull is perhaps the least spectacular of any in this post - but it is nonetheless quite important owing to its age - there are not a whole lot of early Miocene fossil dolphins from New Zealand. The skull must have been pretty severely eroded by the time of discover; parts are reasonably well preserved. Critically, there are two teeth preserved that rather closely match the teeth of the holotype skull of Prosqualodon davidis from Tasmania (now lost, unfortunately): they are uniquely very rugose with strongly developed reticulating ridges that run along the long axis of the tooth, and also have little nodules on the ridges. Most of the features that link this specimen with Prosqualodon davidis, however, are all features of the cranial vertex - for example, the premaxilla extends so far posteriorly that it actually contacts the supraoccipital.

The endocast of aff. Prosqualodon davidis, with adhering bone fragments. From Tanaka et al. (2022).

Evolution of the endocranial space in dolphins, from Tanaka et al. (2022).

However, the real value of the specimen and the point of the study is addressing something that can only easily be studied because the skull is so fragmentary: the endocranial cast. The skull fragments have been prepared in isolation from the endocast, so that you can physically examine the endocast itself - no CT scan required (which is logistically and financially difficult in New Zealand). The endocast of Prosqualodon is not the first - there was apparently an endocast made of the type specimen, which perhaps was reassembled (indeed, the original photographs show some large fractures and a black void on the inside of the braincase) - but in general, it shows a shallow sylvian sulcus/fissure (a groove between the temporal lobe below and the frontal and parietal lobes above), a prominent median fissure (separates the two cerebral hemispheres, generally quite common in mammals), and a prominent olfactory lobe filling what would have been the olfactory fossa of the cranial vault. Modern dolphins cannot smell - they have no cribriform plate or olfactory bulbs, and in fact have also lost/turned off some genes relating to olfaction*. This indicates that Prosqualodon likely retained a sense of smell, perhaps not surprising as other stem odontocetes like Agorophius and Squalodon still had cribriform plates. The sylvian fissure is poorly developed in archaeocetes, but very strongly developed in modern delphinoids - Prosqualodon therefore shows an intermediate condition in this regard as well.

*Mysticetes, surprisingly, retain some sense of smell.

The holotype of Nihohae matakoi under preparation by Andrew Grebneff. Photo by Ewan Fordyce.

The incredible holotype skull of Nihohae matakoi - with Carolina Loch's arms in the background; the original uncropped photo with Carolina is paywalled on the Otago Daily Times.

The holotype skull of Nihohae matakoi in dorsal and ventral views, with a close look at those incredible incisor tusks. From Coste et al. (2023).

Little was published on Oligocene fossil odontocetes from New Zealand for several years until Ambre Coste's first thesis publication came out in the Proceedings of the Royal Society last year (Coste et al., 2023). In this paper she published a phenomenal fossil, one which, whenever Ewan would show photos of it in talks, drew audible gasps from the whaleontologists in the room. Indeed, the specimen - OU 22397 - is perhaps the most spectacular odontocete from the entire Otago collection. The spectacular skull was discovered at Tokarahi/Island Cliff, in a fallen block of limestone, nearby the type locality of Tokarahia kauaeroa as well as the giant fish Megalampris keyesi. Formerly identified by Christian de Muizon as a possible "dalpiazinid", in more recent years the Otago lab came to realize it was likely to be another waipatiid. Coste et al. named this specimen Nihohae matakoi - the genus name meaning slashing teeth, and the species name meaning sharp face in Maori. The braincase of Nihohae is quite similar to Waipatia in overall shape, though it is a bit more 'squat' and considerably flatter, and with a narrower intertemporal constriction. It's also small: the skull width is about 20 cm or so*, as compared to nearly 25 cm in Waipatia and 26 cm in Otekaikea. The entire skull of Nihohae is about 66 cm long, including the tusks - about 10 cm shorter than Otekaikea huata. The periotic is very, very similar to Squalodon and has all of the hallmark features of Waipatia; the bulla notably lacks an anterior spine, which Fordyce (1994) considered to simply be broken in Waipatia. However, Geisler et al., 2011, considered the spine in Waipatia to be rather short, and not homologous with the elongated spine seen in Platanistidae and Squalodelphinidae - and this seems to confirm the absence of a clear platanistoid feature.

*I've realized now that the measurements of Nihohae did not make it into the paper or into the supplementary materials, and had to measure this in ImageJ.

The skull, rostrum, and mandibular teeth of Nihohae matakoi in lateral view. From Coste et al. (2023).

The earbones (tympanic bulla and periotic) of Nihohae matakoi. From Coste et al. (2023).

Everything really interesting in Nihohae, however, is really in the teeth. The tip of the snout is studded with elongate incisor tusks that stick out forward and laterally (sideways). The three incisors are of nearly identical length; the canine is missing, but the first premolar is still procumbent and quite long, suggesting that the canine would have been nearly as long as the third incisor; the teeth become shorter and more vertically oriented posteriorly. The cheek teeth are double-rooted, as in Waipatia, but generally do not have any cusps (some have a single cusp on the posterior side) - they are triangular, with sharp cutting edges. (There are a number of Nihohae-like specimens from the Oligocene of Charleston with similar teeth, I might add). Coste et al. (2023) considered that these unusual incisor tusks, owing to their horizontal orientation, were perhaps used as a sawfish-like slashing mechanism during feeding. Indeed, the right first incisor is broken off and worn down to the gumline - certainly suggesting violent use, and possibly supporting such a feeding behavior. The rostrum is flattened, perhaps making the snout more hydrodynamically efficient during lateral sweeping. My giant dolphin, Ankylorhiza, also has procumbent incisor tusks - but they are much larger in diameter and stouter, and entirely anteroposteriorly aligned - possibly used for ramming prey. Such a behavior is unlikely in Nihohae, given the somewhat radial orientation and more delicate tusks - and also likely excludes intraspecific combat (but not social display). An anterior procumbent tooth that was examined under a Scanning Electron Microscope revealed rather simplified enamel lacking Hunter-Shreger bands, meaning these teeth were unlikely to be loaded with large forces during biting. These teeth further lack wear associated with 'substrate interaction' - an earlier hypothesis held that these teeth may have been used for probing sediment, but tooth wear does not support this.

The phylogenetic analysis from Coste et al. (2023), showing a monophyletic Waipatiidae.

Coste et al. (2023) recovered a monophyletic Waipatiidae in their phylogenetic analysis, including Waipatia, Nihohae, Awamokoa, Otekaikea, Urkudelphis from Ecuador, and Ediscetus from South Carolina. The group was supported by several dental features including the possession of tusk-like incisors (also present, however, in Squalodontidae), having a shallow pterygoid sinus and thick cochlear portion of the periotic, and lacking a ventromedial crest on the bulla. These are features that are somewhat convergent with other stem odontocetes. Interestingly, this version of Waipatiidae was positioned on the odontocete stem - more congruent with analyses derived from the Geisler and Sanders (2003) matrix, like the analyses I've published with Geisler on South Carolina odontocetes.

The future holotype of Nihoroa reimaea, as it was on display at Otago Museum when I first saw it in spring 2012. I was blown away: this is still perhaps the most beautifully and completely preserved Oligocene dolphin skull ever found, anywhere. Photo by me.

The holotype skull of Nihoroa reimaea, from Coste et al. (2024).

The holotype left periotic, left tympanic bulla, and teeth of Nihoroa reimaea, from Coste et al. (2024).

Two more papers on waipatiid dolphins were published in the edited volume "Fossil Vertebrates of Southern Zealandia" in the Journal of the Royal Society of New Zealand. The first of these names another rather spectacular "tusker" (as Ewan called them), named Nihoroa reimaea, by Ambre Coste et al. (2024). The genus name in Maori means "long teeth" and the species name means "emerging ivory", referencing the still-erupting teeth of the specimen. The holotype was collected from the glauconitic lower part of the Otekaike Limestone at Awamoko stream and nearby the Awamokoa type locality - but higher stratigraphically, and generally at a similar horizon to Nihohae and Waipatia. Nihoroa is known from a single skull, but it is perhaps the most beautifully preserved single odontocete skull ever discovered from the southern hemisphere: it is 100% complete, aside from the delicate jugal bones, and completely undistorted. The thing looks like it was buried yesterday. I first saw the specimen on display across the street at the Otago Museum, where it, along with the "Chocolate whale" (see part 2) were on long term loan for exhibit. The skull of Nihoroa is small, 17 cm wide - about the same size as Papahu. The entire skull is about 48 cm long or so. It has a long rostrum, the anteriormost quarter of which is formed entirely by the premaxilla - and this bears three elongated incisor tusks, just like Nihohae. Further, they are oriented horizontally and splay out laterally, suggesting a similar adaptation towards sawfish-like lateral slashing, as Coste et al. (2023) proposed for Nihohae. However, the incisors are quite a bit less erupted than in Nihohae - suggesting that perhaps the specimen may either be a subadult, or perhaps a female in a sexually dimorphic species (e.g. like modern beaked whales). The posterior end of the premaxilla of Nihoroa is split by a cleft, as in all other waipatiid dolphins, but this cleft is shifted very far anteriorly, to the anterior margin of the bony nares - a rather unique condition amongst archaic odontocetes.

Crown shape (ratio between crown length and width at its base; longer teeth on the left, shorter teeth on the right) and the crown angle (straighter teeth towards the top, more recurved teeth towards the bottom) help define what tusks and tusk-like teeth are in Odontoceti. From Coste et al. (2024).

Coste et al. (2024) surveyed modern and extinct odontocetes for big teeth and classified them into three groups: species with tusks, tuskless species, and species with tusk-like teeth. Tuskless species include most modern odontocetes aside from the narwhal (Monodon) and the extinct species Odobenocetops - are the only cetaceans described as possessing true tusks. Beaked whales (Ziphiidae), commonly described as having tusks, are classified by these authors along with waipatiids, Squalodon, and other archaic odontocetes as having "tusk like" teeth, an intermediate form that seems to have evolved many more times in parallel than true tusks. In archaic odontocetes with tusk-like teeth, there is typically a longer section of the rostrum formed only by the premaxilla - which logically follows given that the incisors are typically the elongated teeth, and they are housed entirely in the premaxilla. Tooth shape analyses suggest that incisors that are very straight, and have very long crowns, might end up being synapomorphies for the Waipatiidae*. Possessing tusk-like teeth, versus lacking them, was defined after their analysis as teeth that are quite procumbent and straight, with an angle between the root and crown over 130* (180* being straight, like a narwhal tusk, and closer to 90* being a tooth that points ventrally towards the mandibular teeth). Another factor is the crown shape: the ratio between the length of the crown and the greatest diameter of the crown at its base. Most odontocetes with tusk-like teeth or true tusks have crown widths that are less than 60% of the length of the crown, down to around 3-5% in narwhals. There is considerable overlap with non-tusk bearing cetaceans, many of which have teeth that have widths about 40-60% of crown length, but when combined with the crown angle, it divides all odontocetes into two very clear categories. True tusks are defined based upon being ever-growing. There is no universal agreement about what constitutes a tusk in mammals, with some definitions resorting to relative size difference between teeth, whether the tooth is continuously growing, or if the candidate tusks are 'extra-oral' - e.g. if they stick out of the mouth all the time.

*However, I know of at least one specimen of Agorophius, clearly unrelated, that has similar teeth - so it's possible, like the articular rim of the periotic, that having procumbent tusk-like teeth might be a transitive, 'primitive' stage of odontocete evolution.

Photo I took of what is now the Aureia rerehua holotype while it was being prepared by Sophie White and Nichole Moerhuis in 2013.

Another photo I took of what is now the Aureia rerehua holotype while it was being prepared by Sophie White and Nichole Moerhuis in 2013.

The lovely holotype skull and mandible of Aureia rerehua, from Meekin et al. (2024).

Holotype periotic and tympanic bulla of Aureia rerehua, from Meekin et al. (2024).

The second fossil dolphin named in the Fossil Vertebrates of Southern Zealandia was part of Shane Meekin's master's thesis, which I was proud to have been an external examiner for (my first time with such an honor!) and named Aureia rerehua by Meekin et al. (2024); aureia translates to "cloak pin" in Maori, referring to the long teeth, and rerehua means 'beautiful' in Maori - after the unusually well preserved facial region of the skull. This specimen was excavated from Hakataramea Quarry just before I got to New Zealand, but opened up in the lab in summer (=southern winter) 2013 if memory serves, and I actually posted some photos of the specimen on my blog many, many years ago. The specimen was collected from pretty high up in the Otekaike Limestone if memory serves, within the upper five meters (most of Fordyce's excavations after 2010 were all in this upper zone), dating to about 22-24 Ma. The skull is quite nice - it's missing the basicranium and tip of the rostrum but the facial region is beautifully preserved, and there's a rather nice mandible; many of the teeth are still in situ. It also happens to have beautifully preserved earbones. It looks a bit like Nihoroa at first glance - similar facial region, the posterior end of the premaxilla is anteriorly shifted, but not quite as far, and it is quite small - the skull width is about 20 cm. It really looks like Nihoroa, with an identical shape of the rostrum, small and squat zygomatic process, I can't help but think that they could be congeneric. But that's an idle thought for later. The Aureia holotype has a much more completely preserved dentition, and the postcanine teeth are surprisingly long for a waipatiid - they look like the teeth of Platanista, to be honest, and are uniquely double rooted AND long-crowned at the same time - no other odontocete has teeth like this (except for, ironically, Nihoroa). Confusingly, there are a handful of single-rooted teeth that appear to be from the posterior end of the tooth row with the shortest crowns in the dentition, and some of the only teeth bearing accessory cusps. Like Nihohae and Nihoroa, there are isolated, procumbent tusk-like incisors which fortunately fell out of the rostrum and shifted around before burial - saving them from the quarry bulldozer. The rather more homodont condition in Aureia is similar to Otekaikea, which happens to its sister taxon; it also shares with Otekaikea, and Awamokoa, a fossa in the squamosal to receive the articular rim of the periotic. Aureia retains a cribriform plate, but the space for the olfactory bulbs is highly reduced, indicating a reduced sense of olfaction and perhaps a rather messy pattern of multiple losses of olfaction within Odontoceti.

The holotype teeth of Aureia rerehua, from Meekin et al. (2024).

Phylogenetic analysis from Meekin et al. (2024) showing a monophyletic grouping of Waipatiidae, including Aureia rerehua.

The phylogenetic analysis from Meekin et al. (2024) further supports waipatiid monophyly, a welcome development. These dolphins form three groups: Waipatia-type, Nihohae-type, and Otekaikea-type waipatiids. Waipatia-type species have moderately elevated cranial vertices and the highest degree of postcanine heterodonty, with numerous accessory cusps and double-rooted teeth with widely separated roots; this group includes Waipatia spp. and Awamokoa. Nihohae-type dolphins have flattened facial regions, triangular cheek teeth with mostly smooth cutting edges, and wide mesorostral grooves; this includes Nihohae, Nihoroa, and Ediscetus osbornei from South Carolina (and, in my opinion, several additional South Carolina waipatiids; however, Ediscetus has a very highly elevated vertex). The third grouping, the Otekaikea-type dolphins, have intrapremaxillary foramina, nearly homodont teeth, and a higher degree of postcanine root fusion, wiht the roots only divided down within the socket, and bearing a long 'isthmus', as well as triangular temporal fossae like many Crown Odontoceti; this grouping includes Otekaikea spp. and Aureia rerehua.

The holotype skull of Fordycetus taitonga in dorsal view. From Tanaka et al. (2026).

The holotype skull of Fordycetus taitonga in left lateral and right lateral view. From Tanaka et al. (2026).

One last study to add - I delayed posting this for a while, and in the time being, Yoshi Tanaka managed to publish on a specimen from the Mount Harris Formation (the same unit that produced some of the NZ material of Prosqualodon). If you recall from earlier, the Mount Harris Formation is early Miocene in age and directly overlies the Otekaike Limestone. The newly reported specimen is a partial skull found in a sandstone concretion, and named Fordycetus taitonga - meaning 'Fordyce's whale' and 'southland'. The Fordycetus taitonga holotype consists of much of the vertex and supraorbital region of the skull, a squamosal, and part of the base of the rostrum. It was partially acid prepared. The specimen has a very steep vertex, just like other squalodelphinids, and large blocky nasal bones that almost contact the supraoccipital. The antorbital process is domed, as in other squalodelphinids. One unique feature is the presence of a window in the frontal just behind the optic canal - the overlying maxilla is exposed in this window. This feature was previously thought to be unique to xenorophids - and Yoshi et al. report it for the first time in the Amazon river dolphin, Inia geoffrensis - which is a lovely surprise to me! I've got some codings to update in our odontocete matrix. Yoshi ran a phylogenetic analysis, and in it, Fordycetus plots out as the sister taxon to Squalodelphis fabianii from the lower Miocene of Italy.

Ewan and I on our way to submit my thesis in January 2015.

You always expected to be photographed at Otago, and not just by Ewan (especially if he was in an exuberant mood) - here is my officemate Yoshi and Ewan taking a photo of me at the same time just before I delivered my thesis copies to the Clocktower building for review.

Conclusion and Prospectus

The cetacean fossil record of New Zealand is, aside from the Oligocene, rather sparsely sampled - but the Oligocene record is nothing short of spectacular. Many revelations have come from this part of the world - first and foremost, that archaeocetes survived into the Oligocene alongside the earliest echolocating whales and the earliest baleen whales. Second, Ewan's research of Waipatia and the discovery of many other early odontocetes revealed exactly what early dolphins looked like, and that they were probably capable of echolocation very early on. While Waipatia, in isolation (or, had any of these other species been found first), seems like a "missing link" in dolphin evolution, they were - just like modern species - surprisingly diverse, with half a dozen species of waipatiids (and others) present at any given horizon within the Oligocene. The Kokoamu Greensand doesn't have much in the way of fossil dolphins - perhaps resulting from taphonomic bias, as the Kokoamu mysticetes are plentiful but highly bioeroded, and perhaps the smaller, more delicate (and less voluminous) skeletons of dolphins were much more easily consumed in their entirety. Lastly, there is a myriad of fossil mysticetes (honestly surprised that my labmate Felix Marx hasn't yet published a paper with the subtitle "Myriad of mysticetes" yet, he does love his alliteration! Felix, if you're reading this, go right ahead) from New Zealand including my favorite group, the Eomysticetidae, but perhaps more critically, some of the earliest representatives of crown group mysticetes. There are many critical discoveries that have yet to be published - Josh Corrie is still working on OU 22294, the world's only nearly complete kekenodontid skull; the "Chocolate Whale", the "Oligocene right whale", and Mauicetus parki and friends (e.g. ZMT 67) await study and publication; and of course there are dozens of odontocete specimens, like the Milburn and Earthquakes squalodontids, and several more dolphins from Shane Meekin's thesis.

Ewan's office, circa 2014, how his students will remember it: slightly cluttered, mostly reasonably organized; we've all sat in those red chairs. Photo by Yoshi Tanaka.

Our multi-use table in the Otago Geology Museum - here, the end is set up as a photography studio as it frequently was. Setting up the lights to Ewan's specifications (or, with a few corners cut, if we strategically did it after hours) took so long, that we frequently would treat it like an assembly line once the photos looked "right". Photo by Yoshi Tanaka.

Most of these discoveries, and virtually all of the recent research on fossil cetaceans, stemmed from the mind and efforts of the venerable Dr. R. Ewan Fordyce, who passed away one year ago (Nov 10, 2023) today as I write this (I originally wrote this last fall). Ewan was a great doctoral advisor, and while at times his lab was too large for all of us to get the necessary attention, he was generous with his time, an extremely careful person in all regards, with a warm heart and indefatigable spirit. In a way, Ewan will never really leave us: his goodwill has generally permeated our quaint little field, contrasting with the science "red in tooth and claw" that has tainted dinosaur paleontology. His entire approach to how we study fossils has influenced if not drastically changed most of the field. Every time I take photographs of a fossil or work on editing my figures, I can practically hear him reminding me "It's a bit tricky" or "it's not quite right, let's move that diffuser over just a bit". Every time I work on a manuscript, I ask myself "What would Ewan have done?" Ewan tirelessly worked to bring the incredible fossils of New Zealand to the world stage - and it's now the responsibility of 'whaleontologists' around the world to take the plunge and visit the bottom of the planet and see these spectacular fossils directly. It's a long trip - but it's worth the time.

A farewell to Ewan Fordyce (1953-2023).

On a different, and perhaps more somber, note, all of this is threatened by budget problems at my alma mater. In 2023, the Department of Geology was very close to hiring a replacement for Ewan's position. At the last minute, before shortlisted candidates could be interviewed, the whole process was called off and a campus-wide hiring freeze instituted. We don't know how long this hiring freeze will last. Marcus Richards, the colleague who I thought was best-suited to replace Ewan, has now left the University altogether (though is now working across the street at Otago Museum). Ewan's colleague, Dr. Daphne Lee, Professor Emerita in the department and "brachiopodologist" as Ewan referred to her specialty (brachiopods, for the unfamiliar reader, are superficially bivalve-like invertebrates - and surprisingly common in these whale-bearing Cenozoic rocks) - has been involved in digitizing the collection over the past few years and has kept busy in retirement by taking up Ewan's mantle. Jeffrey Robinson - Daphne's former Ph.D. student - is spearheading the digitization effort, which began back in 2021. The Otago collection was catalogued in a series of bound books, and no digital catalog ever existed - a natural result of the old age of the collection, and hardly an unusual one. [As an aside, Daphne, as we knew her, was usually the second paleontologist on our commitees, including my own - and I had several pleasant yearly review meetings with her and Ewan].

Our brave "brachiopodologists" at University of Otago - Professor Emerita Daphne Lee on the left, and Jeffrey Robinson on the right, holding the physcal books that make up the Otago Geology Museum catalog. When I arrived, and left, Otago, these were the only copies of the catalog.

In 2012, while we were trying to find work for Sarah, she offered to start digitizing the catalog into excel, like she had done in the years prior at Museum of the Rockies. Sarah did not explicitly mention employment, hoping it might be offered, but willing to volunteer; however, Ewan's response was lukewarm. We weren't sure why at the time, but after three more years of working with Ewan, and then essentially running a similarly sized museum on our own with zero help for a decade, I have a pretty good idea. I'm sure it had something to do with simply not having enough free time to devote to guiding someone who was unfamiliar with the collection (training a volunteer is time consuming on its own, but a new employee or longer term intern takes quite a bit more effort). In a way, at the time, it was a job that only Ewan could have done, and he never had time to train another Ewan, so to speak. None of us Ph.D. students had the breadth of knowledge for such a task beyond the small parts we were familiar with. One unfortunate byproduct of being so deftly competent at so many different things is that Ewan insisted on doing many of them himself and certainly did not have time to do them all. He also had a bad habit about not delegating tasks. Had it been anyone else, we might have felt offended that we weren't trusted to do the right thing - but that's just the way he was - and, truth be told, he clearly loved doing them all - and I think that's really what it was all about. But, don't misinterpret my words here: there is a warning present. I have learned over the years, sometimes painfully, about not becoming 'too useful' or the only one in a workplace capable of doing such tasks. Because, eventually, they all pile up at the same time, and you'll have to pick and choose. Carefully, though, because nobody likes being told 'no'.

Otago preparator Sophie White, now enrolled in the doctoral program herself, is busy packing up some casts of Waipatia for overseas shipping. I suspect this one was being mailed to Japan; I think the one in the foreground was packed into my suitcase to deliver to Charleston Museum (who, bizarrely, refused the gift and it ended up at the Smithsonian instead).

Work continues on the collection. Sophie White, now pursuing a Ph.D. in forensic zooarchaeology in the Department of Forensics at Otago, is still involved with the museum and doing preparation in the lab part time. Fossils continue to be published by Ewan's students and his colleagues, many of which were featured in the 2024 special volume Fossil Vertebrates from Southern Zealandia. Another excellent new publication, Fossil Treasures of the Otago Geology Museum, a bit more of a popular book with lovely images - more like a 'coffee table book' - was recently published by Daniel Thomas, Jeffrey Robinson, and Daphne Lee. Many of our prime cetacean fossils are featured prominently, including Tohoraonepu, Waipatia, Tokarahia, and Toipahautea (which you should be familiar with by now!). This new book is available to read free here (and can be downloaded as a pdf here). I still need to order a physical copy as this is clearly a must-have for my own library.

My anxiety about the collection has been somewhat calmed and subdued over the past few years with the news of this digitization effort by Jeffrey and Daphne. But I would be lying if I said I was not worried. While there are competent and knowledgeable scientists carrying on, Fordyce's position has still not been filled - now over two years later. Professor Lee has retired after all - she is now Professor Emeritus. Ewan deserved a retirement, and quite frankly, so does Daphne. Will the University ever hire someone to fill Ewan's shoes? They are incredibly large shoes to fill - and, I know I am speaking for virtually everyone in his expsansive cadre of former students and colleagues - it may not be possible to replace Ewan. But, with the size of the collection and the vast opportunity for many future discoveries on the South Island - the opportunity remains to hire someone flexible enough to become the next Ewan Fordyce. Picking the right person will necessarily be difficult.

There's a lot of work left to do - copied from the prior post: all of these are unprepared or partially prepared plaster jackets in the basement of the Otago Geology Department/Museum. Can we maintain the status quo in the fight against entropy, or will we be able to hire another Ewan Fordyce? That person is alive right now, if they - and the University of Otago - can rise to the occasion. Photo by Cheng-Tsiu Tsai.

Ultimately, the long-dead fossilized remains of ancient beasts cannot speak for themselves. Those remains which Ewan devoted his career to have outlived him - and with luck, they will outlive their current stewards (Lee, Robinson, White) - and outlive me, Yoshi, Tsai, Felix, Josh, Gabriel, Carolina, Hiroto, Richard, Shane, Ambre, Katy, Tatsuro, and others - but that can only happen if they are cared for by someone who can speak for them. Though we strive to bring these old bones to life, the skeleton of Kairuku cannot waddle over across the courtyard to the Clocktower building and demand a meeting with an administrator. There are dire consequences otherwise - other university museums have been split up and sent to different colleges (we received the teaching collection from Uppsala University at MSU in the mid 2000s after their department was shuttered), others have been sold off, and others have been ordered to be transferred or discarded. In one case, administrators at one university ordered the university museum to transfer several million specimens to another institution, ostensibly to make space for the track and field team - otherwise, the collection would have to be thrown away - literally - in the trash. Will the Otago collection be discarded into local landfills? This was, after all, the fate of the "Mauicetus" lophocephalus holotype, on Otago campus, within living memory. I currently don't view this as being likely, especially given the attention paid recently by Jeffrey and Daphne.

But is the status quo enough? The status quo, even when Ewan was in charge - was absolutely not enough then, and even if the university reopens the position and hires someone who can fill those enormous shoes - the collection deserves more. After all, Ewan explained to us that work with the museum and collection was essentially volunteer work for him, and that he was chiefly employed as a professor to teach the basin studies class for the department. Most of his funding for the museum was external - with not much internal support. The biggest funders were National Geographic, the National Lottery, and later on, Marsden grant funding (which have recently had its own set of problems plagued by NZ politics). The university has such a unique opportunity to do more with the museum - and for not much funding, let's be honest: hire the right couple of people at a competitive salary, and that little museum is off to the races. The museum already has an incredible suite of field equipment, an incredible lab - it just needs salaries. There is simply so much that can be done with what already exists - new fieldwork on the South Island, a veritable mountain of fossils to prepare from plaster jackets, and a host of completely prepared fossils awaiting study - and of course, unfinished research projects of Ewan's deserving their completion. I hope that the University, and the Department of Geology, fundamentally understand what a treasure trove they are already sitting on, with a century's worth of research opportunities - rather than short-sightedly viewing it as an albatross around their neck.

Lastly, there is a new fund supporting paleontological research at the University of Otago - the R. Ewan Fordyce Paleontology Fund. Please consider donating, here.

Many thanks to Sophie White for commentary on these posts.

Ewan with some cut-out tracks of giant moa - his last large excavation, if memory serves.

References

Aguirre-Fernández, G., & Fordyce, R. E. (2014). Papahu taitapu, gen. et sp. nov., an early Miocene stem odontocete (Cetacea) from New Zealand. Journal of Vertebrate Paleontology, 34, 195-210.

Benham, W. B. (1935). The teeth of an extinct whale, Microcetus hectori n. sp. Transactions of the Royal Society of New Zealand, 65, 239-243.

Benham, W. B. (1936). Fossil Cetacea of New Zealand III. The skull and other parts of the skeleton of Prosqualodon hamiltoni n. sp. Transactions of the Royal Society of New Zealand, 67, 8-14.

Benham, W. B. (1937). Fossil Cetacea of New Zealand II. - On Lophocephalus, a new genus of zeuglodont Cetacea. Transactions of the Royal Society of New Zealand, 67, 1-7.

Benham, W. B. (1942). Fossil Cetacea of New Zealand V. - Mauicetus, a generic name substituted for Lophocephalus Benham. Transactions of the Royal Society of New Zealand, 71, 260-270.

Camp, C. L. (1942). Ichthyosaur rostra from central California Journal of Paleontology, 16, 362-371.

Coste, A., Fordyce, R. E., & Loch, C. (2023). A new dolphin with tusk-like teeth from the late Oligocene of New Zealand indicates evolution of novel feeding strategies. Proceedings of the Royal Society B, 290, 20230873.

Coste, A., Fordyce, R. E., & Loch, C. (2024). A new fossil dolphin with tusk-like teeth from New Zealand and an analysis of procumbent teeth in fossil cetaceans. Journal of the Royal Society of New Zealand, 54, 738-757.

Fordyce, R. E. (1994). Waipatia maerewhenua, New Genus and New Species, Waipatiidae, New Family, an archaic late Oligocene dolphin (Cetacea: Odontoceti: Platanistoidea) from New Zealand. Proceedings of the San Diego Society of Natural History, 29, 147-176.

Geisler, J. H., & A.E., S. (2003). Morphological evidence for the phylogeny of Cetacea. Journal of Mammalian Evolution, 10(1/2), 23-129.

Marples, B. J. (1949). Vertebrate paleontology in New Zealand. Tuatara, 2, 103-108.

Meekin, S., Fordyce, R. E., & Coste, A. (2024). Aureia rerehua, a new platanistoid dolphin from the Oligocene of New Zealand with a unique feeding method. Journal of the Royal Society of New Zealand, 54, 758-777.

Tanaka, Y., & Fordyce, R. E. (2014). Fossil dolphin Otekaikea marplesi (Latest Oligocene, New Zealand) expands the morphological and taxonomic diversity of Oligocene dolphins. PLoS One, 9, e107972.

Tanaka, Y., & Fordyce, R. E. (2015a). Historically significant late Oligocene dolphin Microcetus hectori Benham 1935: a new species of Waipatia (Platanistoidea). Journal of the Royal Society of New Zealand, 45, 135-150.

Tanaka, Y., & Fordyce, R. E. (2015b). A new Oligo-Miocene dolphin from New Zealand: Otekaikea huata expands diversity of the early Platanistoidea. Palaeontologia Electronica, 18(2.23A), 1-71.

Tanaka, Y., & Fordyce, R. E. (2016). Papahu-like fossil dolphin from Kaikoura, New Zealand, helps to fill the early Miocene gap in the history of Odontoceti. New Zealand Journal of Geology and Geophysics, 59, 551-567.

Tanaka, Y., & Fordyce, R. E. (2017). Awamokoa tokarahi, a new basal dolphin in the Platanistoidea (late Oligocene, New Zealand). Journal of Systematic Palaeontology, 15, 365-386.

Tanaka, Y., Ortega, M., & Fordyce, R. E. (2022). A new early Miocene archaic dolphin (Odontoceti, Cetacea) from New Zealand, and brain evolution of the Odontoceti. New Zealand Journal of Geology and Geophysics, 66, 59-73.

Tanaka, Y., Ortega, M., & Fordyce, R. E. (2026). A new squalodelphinid species with a domed supraorbital process from the lower Miocene of New Zealand. Journal of Vertebrate Paleontology (online early).

Field snapshots: a very brief trip to coastal Oregon

2026-04-05T23:42:00.000-07:00

n mid February I was invited by my colleague Dr. Win McLaughlin to give a talk at Southwestern Oregon Community College (SWOCC) which has a pretty fantastic science program. Win flew me up for the presentation and a couple of days of fieldwork during a rare dry spell on the perpetually rainy Oregon coast. I had not visited in over a decade, and was thrilled at the opportunity! Here is a bit of a slideshow from my trip.

The channel islands are often not visible from shore owing to fog on our coast, even in sunny socal - to the point where I had no idea until about two years ago that the ones in Santa Barbara could be viewed on a clear day from 101! Every time I had driven 101 before it was foggy. Here is a view of San Clemente Island from my flight, which lies about 70 miles (110 km) off the coast of San Diego.

The Lick Observatory, run by UC Santa Cruz, perched atop the summit of Mount Hamilton. Sarah and I visited the Lick in summer 2024. This is the first mountaintop observatory ever built, and has one of the two largest refractor telescopes ever built (the largest is at the Yerkes Observatory in Chicago, and the Great Lick Refractor is the second largest - but the only still currently in use).

A view of Mount Shasta from the air. You can really tell that it's an enormous stratovolcano from this perspective!

I finally got an opportunity to see "wally" the whale - a balaenopterid mysticete excavated from the Empire Formation near Coos Bay, Oregon. It's about 7-9 million years old. The specimen was excavated by members of a fossil club - NARG, the North American Research Group - an incredible feat for a group of avocational paleontologists. I'm thrilled that the specimen has entered a museum collection. There aren't many complete balaenopterid skulls from the Pacific coast; the only other one from the Tortonian is Parabalaenoptera from the Santa Cruz Mudstone at Bolinas in Marin County.

Here is wally with University of Oregon master's student Andy Quintanilla, who is putting the final touches on the preparation of the skull.

Andy has been working diligently, and owing to a thin veneer of rock in places that is nearly the same color as the bone, she's been leaving these lines etched into the rock as a quick visual reminder of what remains to be removed.

At least one of Wally's tympanic bullae (outer ear bones) has been prepared quite well! Here it is in ventral view, still articulated with the hidden petrosal/periotic and the squamosal. The likelihood of the bulla being removed from the skull is quite low.

My colleague Dr. Win McLaughlin holding a jaw of the rhino Teleoceras from the Miocene of Oregon that she and others excavated during her master's (during our U. Oregon visit).

A fabulous skull of a squalodelphinid dolphin from earlymiddle Miocene rocks of coastal Oregon. I wonder if the specimen is another example of Dilophodelphis, originally reported from the Nye Mudstone further north in Oregon - or if it is something else.

A partial skull in a very large boulder of an enaliarctine pinniped from the Astoria Formation, found either by Kent Gibson or Weylin Charland (I can't remember, but I think Kent rolled it off the beach) The braincase is on the right, and the rostrum is to the left and worn away; you can also make out the left and right zygomatic arches at top and bottom.

A sculpture of a mammoth outside the University of Oregon Museum of Natural and Cultural History. The sculpture was inspired by a mammoth trackway found at Fossil Lake in Oregon.

I accompanied Dr. McLaughlin around her farm during her morning chores. Here she is feeding her horses.

The Highway 101 bridge into North Bend over Coos Bay.

The morning of my talk, Dr. McLaughlin and I went to the type section of the Empire Formation along the shore of Coos Bay. In one large tidepool I saw more kelp crabs (Pugettia producta) than I had seen during my entire life. There were hundreds, if not thousands - and they were all large! Fortunately, I had my waterpoof Olympus camera and plunged my arm into the water for a few minutes. It was sooo goddamn cold - I think it was around 48-50 degrees.

I still have no idea why there were so many present. Win speculated that they were blown into the cove by currents, and that it had happened before in the winter in Coos Bay. The bedrock here is upper Miocene Empire Formation - you can make out a well-preserved scallop (Patinopecten oregonensis) immediately adjacent to the large reddish kelp crab!

Dr. McLaughlin summoning every serious fiber in her body to point out the location of the excavation site for "wally" the whale.

A beautifully preserved specimen of the scallop Patinopecten oregonensis.

A cetacean vertebra preserved in the Coos Conglomerate, which is a younger unit that cuts into the Empire Formation; this vertebra was probably eroded out of the Empire Formation.

Clinocardium (coosense or meekianum) from the Coos Conglomerate - reworked in a small concretion from the Empire Formation.

Dr. McLaughlin at Fossil Point - the type locality for the Coos Conglomerate.

Three rings - my wedding ring as scale for two large fish vertebrae; these are most likely Oncorhynchus rastrosus, the saber toothed salmon (formerly "Smilodonichthys").

Some kind of clam (Protothaca perhaps?) sporting a beautiful example of a borehole from a moon snail (Naticidae).

A reworked clam, possibly a Spisula (surf clam). It died and opened up after death, in soft enough sediment to permit the shell to open up, or on the seafloor - and then a small concretion formed prior to being reworked from the Empire Formation and into the Coos Conglomerate. This photo also highlights how many mollusks did not 'survive' like this and were fractured into little bits.

A rather large slipper snail, Crepidula princeps, from the Coos Conglomerate. This one was about 12 cm wide - one of the largest I had ever seen (until last week at Capitola in the Purisima Formation, stay tuned...)

Another lovely Patinopecten - this time, preserved in the Coos Conglomerate rather than the Empire Formation (though this is likely reworked from the latter).

My old friend Kent Gibson showed up and put together a great show and tell table with his many fossils from further north along the Oregon coast.

And I met some new collector friends - this is Jon Lang of Bandon, Oregon, who found this spectacular sandstone concretion with about twenty or so baleen plates preserved in three dimensions! Fragments of the palate are also preserved. One earlier specimen was reported by Earl Packard in the 1940s, but this specimen is much, much nicer. A couple of specimens have been reported from California in conference abstracts, and that *is it* for fossils of baleen outside the spectacular Pisco Formation of Peru. The crazy thing is that Jon straight up gave me this specimen for study! I couldn't believe it. I had to rearrange some of my stuff in my bags for the flight home...

The next morning I had a meeting with the director of the Charleston Marine Life Center (not THAT Charleston). While Dr. McLaughlin taught lecture, she let me borrow her car and I grabbed coffee and some donuts and headed out to eat a nutritious breakfast on the shore of Coos Bay. A bald eagle (Haliaeetus leucocephalus) landed on a tree. I cautiously finished my donut and began assembling my camera and telephoto lens, expecting a trek through the mud to get to it. Before I got on my mudboots it flew off and toward me - I got the camera up just in time to take a half dozen snapshots; they're all quite good, but this one stood out. These may be old hat in the Pacific Northwest, but they're not terribly common in the San Francisco area where I grew up so they'll never get old for me.

At the Charleston Marine Life Center there were plenty of familiar critters in tanks - here is a young individual of the giant rock scallop, Crassodoma gigantea; they look quite scallop like as juveniles before they are fully settled in place and cemented to the substrate. It is surrounded with strawberry anemones (Corynactis californica).

One of the weirder, deeper water denizens of the Pacific coast: the large basket star Gorgonocephalus eucnemis. Basket stars are actually quite closely related to brittle stars, and are in the same order Ophiuroidea (and, therefore, technically a group of highly derived brittle stars); they filter feed, and are ecologically similar to crinoids.

And one unfamiliar to me in California - the unimaginatively named brown box crab - formerly Lopholithodes, but recently reassigned to a new genus Echidnocerus since Lopholithodes had apparently already been used. These unusual crabs are an unusual looking type of king crab - they are members of the Anomura, and like Alaskan king crabs, hermit crabs, and porcelain crabs - they only have three pairs of 'legs' unlike the true crabs, known as the brachyurans.

A lovely skeletal mount of a gray whale (Eschrichtius robustus) at the Charleston Marine Life Center. They have wonderful tanks below, and skeletons above.

Distinctive shell beds in the Pleistocene Port Orford Formation dominated by the tiny clam Psephidia.

A beautiful little gastropod, perhaps 2 cm long - no doubt something related to Nucella. I think this one is likely to be Nucella canaliculata (channeled dogwinkle).

This sort of in-situ weathering is common in mines in the southeastern USA, but is relatively rare on the Pacific coast - here, there are some platforms where the shell beds weather out from the rain and the shells just get cleaned off and sit there.

A beautiful clam that has weathered out of the siltstone of the Port Orford Formation.

Another clam that weathered out, just a few months too early for us.

A particularly gorgeous tall-spired gastropod - I'm not sure what it is, perhaps a Beringius.

A variety of clams weathering out - a multitude of minute Psephidia clams, several larger ones including Spisula or Cryptomya, and a rare example of a California mussel, Mytilus californicus.

A closeup of the California mussel, Mytilus californicus.

After a few hours it was time to head back and grab some food in Bandon. We stopped to photograph some tremendously large tree stumps which have been here for likely hundreds or thousands of years, and are driftwood that washed up on the beach, likely during storms, and then buried under a large sand dune - which is now eroding away, exposing the stumps.

The next day we visited Kent and Lucy Gibson in Newport, Oregon - my first time to their house since 2012 when I made a visit with Sarah, Ray Troll, and Smithsonian NHM Director Kirk Johnson.

Kent's collection has increased considerably since the last time I visited - everything used to be in this little lab space. Kent uses air scribes, a microblaster, and more recently, acetic acid to prep out specimens. Here is an acid prepared basking shark vertebra (probably Cetorhinus piersoni). Gibson collection.

A chunk of a pinniped skeleton from the Nye Mudstone - five thoracic vertebrae in articulation with a handful of ribs. Likely to be an enaliarctine, Enaliarctos or Pinnarctidion. Gibson collection.

If you're going to find a chunk of a baleen whale skull, it's best to find the vertex of the skull, or this part: this is the squamosal with an in situ periotic bone and part of a tympanic bulla. This one doesn't really need any additional preparation - it probably represents something like Parietobalaena. I do not think it's a specimen of Cophocetus oregonensis - the only formally published baleen whale from the Astoria Formation, published 90 years ago by Remington Kellogg and Earl Packard. Gibson collection.

An unusual specimen: a partial shell of a leatherback sea turtle from the Astoria Formation, belonging to the genus Psephophorus. This is an extinct leatherback with a thicker carapace than extant Dermochelys. The ossicles are quite large - and you can see at the lower left that they form a distinct ridge; in modern leatherbacks, there are five such ridges. Gibson collection.

A gorgeous braincase and basal rostrum of a kentriodontid dolphin from the Astoria Formation - perhaps one of Kent's nicest specimens. At a glance, it seems to compare well with other Pacific basin kentriodontids like Kentriodon nakajimai from Japan, Kentriodon diusinus from Baja California, and Mesokentriodon protohumboldti from Peru - but could conceivably represent the same taxon as one of the Calvert Formation kentriodontids. These dolphins from the Astoria Formation are numerous but have not received much if any study. Gibson collection.

A vastly more incomplete dolphin (?kentriodontid) skull - but one that is still quite anatomically informative as every little suture is very clearly preserved in cross-section. Specimens like this are almost best left unprepared, as mechanical preparation might be incapable of exposing similar detail underneath the concretion (acid prep, however, would do the trick). We're looking at the vomer, nasal passages, and the frontal bones separating the nasal region from the endocranial cavity on the left. Gibson collection.

Kent Gibson showing off his spectacular collection of dolphin skulls from the Astoria Formation (and a few from the Nye Mudstone). Most seem to be Astoria kentriodontids!

A whale vertebra in Kent's garden, overgrown now by moss. Kent made a comment about it starting to break down, but I thought it was rather beautiful in its current state. It struck me as an interesting metaphor for a handful of my own research projects I abandoned when I left the west coast in 2011; as I have grown older, my perspectives and skills have changed and my own observations have increased - the 'moss', so to speak, are all the things I would not have appreciated or thought about had I gone off half cocked and published a crappy paper in my mid 20s. Some things take time.

We stopped at a few spots to try and find puffins - no luck. Here are a bunch of surf scoters (Melanitta perspicillata), which are "sea ducks" that are a common sight along California beaches as well as Oregon. These birds winter in the subarctic and spend the spring and summer along the west and east coasts - though I never, ever saw one on the east coast. They're a very common sight in Half Moon Bay during the summer and I've seen them in Santa Cruz as well, though less frequently.

Dr. McLaughlin happily standing in for scale next to an enormous whale mandible - probably a fin whale (Balaenoptera physalus) by my reckoning - on display outside the Umpqua River Lighthouse near Reedsport, Oregon. A surprising number of modern whale skulls and mandibles have made it into local museums and displays like this after being trawled up off the Oregon seafloor by fishermen.

Dr. McLaughlin surprised me by taking me to a small swampy dell filled with these incredible carnivorous plants - Darlingtonia californica - also known as the cobra lily or the western pitcher plant. This species lives in the cold rainforests of the southern Pacific Northwest, in the northern Sierra Nevada and the coast range of Del Norte County, California, but chiefly in the coast ranges of central and southern Oregon; north of Humboldt County, California, these plants live in a belt along the coast.

Seal Rock State Beach, just south of Newport, Oregon. Several of Doug Emlong's holotype specimens of marine mammals were excavated in this area. Seal rock itself is a volcanic neck made of columnar basalt. No puffins here either =(

Paleontology talk - Fossil whales and dolphins of the Pacific northwest and origin of baleen

2026-02-23T09:19:00.000-08:00

Just before Valentine's Day I was invited by my colleague Dr. Win McLaughlin to fly up to Coos Bay, Oregon, for a few days to give a talk in the Geology Lecture series at Southwestern Oregon Community College. I flew up for a few days (and will have a followup post about the trip in general) and gave my first lecture in a while - and, my first time on this particular topic. I wanted to focus on fossils from the Oregon coast, and ended up incorporating some fossils from Washington as well. If I had my 'druthers I would have been able to discuss simocetid dolphins for longer, but that could have dragged on for another half hour - so I kept my discussion of 'toothed whales' short and sweet, and focused on the teeth to baleen transition within Mysticeti, chiefly focusing on the tooth-and-baleen bearing Aetiocetus weltoni as well as the baleen-bearing eomysticetid whales Maiabalaena and Sitsqwayk.

Watch the entire talk here on youtube here:

I had a blast exploring the Oregon coast for a couple of days, and the talk was received well - thanks to Dr. Win for the invitation! I hope to make it back up there again soon. Here are some sneak previews of the lecture:

The skull of Aetiocetus weltoni and the clearly preserved, but admittedly small, lateral palatal foramina.

Similarity in morphology of the lateral palatal foramina in Aetiocetus weltoni and a modern fin whale (Balaenoptera physalus).

Simplified hypothesis for the stepwise transformation from teeth to baleen in mysticete evolution.

A sampling of Oligocene fossil mysticetes and odontocetes and their place in the transition between Eocene archaeocetes and modern whales and dolphins.

2025 in review: advances in marine mammal paleontology

2025-12-31T03:00:00.000-08:00

It's time for the end of the year roundup - for a while I wasn't so sure that 2025 was going to have that long a list of papers, but we ended up with over fifty, which is about average. Several new papers on Oligocene mysticetes came out, all of which were quite welcome - with the long-awaited redescription of Fucaia goedertorum by Ehecatl Hernandez-Cisneros and Jorge Velez-Juarbe, the new eomysticetid from Baja California Cochimicetus by Cielo Cedillo-Avila and colleagues, and of course, a new (albeit fragmentarily known) species of Janjucetus from Australia reported by Ruaridh Duncan and colleagues. I was also pleased to see several new taphonomic studies, mostly focusing on the organisms that feed on and inhabit marine mammals after death - such as the bone eating worm, Osedax. A book chapter published the first public images of the extraordinarily complete Louisiana specimen of the gigantic archaeocete Basilosaurus cetoides. We had some new papers on desmostylians and sirenians, but I think the real standout this year were papers on archaic odontocetes. My colleague Margot Nelson published three monographic papers from her dissertation research on squalodontids. One focused on redescribing Squalodon grateloupi from the lower Miocene of France, another on revising the taxonomy of the genus and family - a very brave endeavor - and lastly, redescribing the lovely Oligocene squalodontid Eosqualodon langewischei from Germany. In addition, Maximiliano Gaetan and colleagues published a new article describing the entire fossil record of Prosqualodon, and synonymized the Australian (er, Tasmanian) species Prosqualodon davidis with Prosqualodon australis from rocks of the same age in Patagonia. Another Patagonian whale, the early sperm whale Idiorophus patagonicus - was redescribed by Florencia Paolucci et al. A possible tooth of an even larger sperm whale, Livyatan, was reported from southern California; a new beaked whale, Flandriacetus, was reported from upper Miocene rocks of the North Sea - and new specimens and species of the Miocene odontocetes Chilcacetus and Kentriodon were reported. Surprisingly, only a couple of papers on fossil pinnipeds were published - including the surprisingly complete skeleton of Monachopsis by Pavlo Otriazhyi and colleagues from Ukraine. Papers I reviewed are marked by an asterisk.

Now, the usual stipulations apply: I am likely to have missed something, but before you send me hate mail or suggest I include a publication, please double check that it wasn't covered last year. I include papers on this list based on the year they are first published online. If a paper is published online late in the year, but then included within a formal journal issue/volume in the following year, I leave it where it lies (just like in golf, I guess). Preprints, conference presentations, magazine articles, etc. do not count as they are not peer reviewed and do not represent the priorities of contemporary researchers. I am guaranteed to have missed papers in journals that do not post their papers online when first published (e.g. Cainozoic Research, Bolletino della Società Paleontologica Italiana). Once I've received pdfs for any missing papers, I'll include them! Papers must include subfossil or fossil marine mammals (studies on the skeletons of modern marine mammals don't count as paleontological research, even if executed by paleontologists). Multiple papers by the same author are not guaranteed to be in exact alphabetical order. And, lastly, no, I am not going to include complete references nor am I going to format them (and yes, I have been asked this before).

Amane et al. - A delphinid mandible from the Lower Pliocene of Morocco: further fossil evidence of high dietary niche partitioning in true dolphins.

We describe a left mandible of Delphinidae (Cetacea, Odontoceti) from the Lower Pliocene of the Asilah Basin, northwestern Morocco. Despite its fragmentary nature, the specimen reveals key morphological features that support affinities with extant Globicephalinae, i.e., a short mandibular symphysis; a reduced alveolar portion; and a posteroalveolar portion characterized, laterally, by a nearly straight dorsal margin and a ventral margin that sharply curves posteroventrally. However, the Asilah mandible differs from all known extant and fossil globicephalines in its unique character combination, and therefore is here referred to Globicephalinae gen. and sp. indet. pending the discovery of more complete materials. The overall morphology of the reconstructed Asilah mandibles implies a feeding strategy intermediate between suction and grasping. Therefore, this fossil seemingly provides further evidence of a Pliocene generalist delphinid lacking specialized features towards either suction or macropredation, which in turn would have evolved independently multiple times across the family. More generally, this record further supports a high disparity within Delphinidae as early as in Pliocene times, which may correlate with high dietary niche partitioning.

Amson and Boller – 3d Models related to the skull of Miocaperea pulchra

Pygmy right whales, represented by one extant species, Caperea marginata, are highly idiosyncratic baleen whales. Only one fossil of undisputable affinity is known to date, which is also the most complete, the holotype of Miocaperea pulchra (Bisconti, 2012; Marx et al., 2016). This specimen was found in the
Aguada de Lomas site (Pisco Formation, southern Peru) and is assumed to be upper Tortonian of age (Bianucci & Collareta, 2022; Bisconti, 2012). It has been brought to the State Museum of Natural History Stuttgart in the 80s (Bisconti, 2012), where it was mechanically prepared by one of us (MB). The holotype
comprises a sub-complete skull (missing the tympanic bullae) in two parts (See Table 1 and Fig. 1), as well as associated fragments of the mandible and baleen rack. Indeed, this is one of the exceptional cases of preservation yielded by the Pisco Formation, since baleens do not usually fossilize (Bosio et al., 2021).

Asai et al. - New evidence for the co-occurrence of two genera of Paleoparadoxiidae (Mammalia, Desmostylia) from the Middle Miocene of Japan: insights into taxonomic status and paleodiversity in Desmostylia.

Desmostylia, an extinct order of marine mammals, includes two major families: Paleoparadoxiidae and Desmostylidae. Within Paleoparadoxiidae, three genera—Archaeoparadoxia, Paleoparadoxia, and Neoparadoxia—have been identified, with Paleoparadoxia being the only genus found on both coasts of the North Pacific Rim. In Akan, Hokkaido, Japan, one of the largest Paleoparadoxia fossil assemblages in the world has been discovered from the Middle Miocene Tonokita Formation. Previous studies suggested the presence of two congeneric species of Paleoparadoxia, while recent taxonomical revisions raise the possibility that two genera, Paleoparadoxia and Neoparadoxia, were present in Akan. Here, we describe three paleoparadoxiids specimens from Akan, which consist of two partial crania and a mandible. Based on morphological comparisons and phylogenetic analysis, we identified these specimens as Paleoparadoxia sp. and Neoparadoxia sp. This represents the first record of two genera of Paleoparadoxiidae in the same locality and horizon, with the potential to provide valuable insights into cladogenesis and morphological diversification within this family. In addition, the Akan specimens exhibit mosaic characteristics of Paleoparadoxia and Neoparadoxia, suggesting that a reassessment of their morphological features for taxonomic identification and phylogenetic analysis is required. To better understand species-level diversity patterns in Desmostylia, we conducted stage-binned analysis and richness curve analysis. Our analysis revealed three significant points in their diversification history: (1) Desmostylidae reached peak diversity at the Oligocene-Miocene boundary, coinciding with a glacial event; (2) Paleoparadoxiidae achieved peak diversity during the Middle Miocene global warming event; (3) both families declined in diversity and went extinct during the Middle to Late Miocene global cooling event. These findings indicate that desmostylian diversity could have been closely linked to climatic events, with the differing peak diversities of Paleoparadoxiidae and Desmostylidae reflecting their respective preferences for warmer and cooler climates. Our analysis provides a valuable baseline for understanding the diversity and evolutionary history of Desmostylia.

Baldanza et al. – Scavengers and opportunists at work in the deep sea: decapods, echinoids, and fishes.

The early Pleistocene whale fall events recognized at the Bargiano site (southwestern Umbria, central Italy) provided the opportunity to document and reconstruct the community of scavengers and opportunists, vertebrates and invertebrates that gathered around cetacean remains. A rich fauna of ghost shrimps and brachyuran crustaceans (the most represented ones), teleost fish and other osteichthyes (i.e., Ophidiiformes and Sciaenidae), sharks, as well as some specimens of irregular echinoids, have been analysed. The occurrence of otoliths of the rare ophidiid fish Hoplobrotula orcianensis Schwarzhans, 1994 and the irregular echinoid Ova canalifera (Lamarck, 1816) are herein reported for the first time in early Pleistocene marine deposits from Umbria. Among the decapods, Jaxea nocturna Nardo, 1847, Goneplax rhomboides (Linnaeus, 1758), and Asthenognathus alleronensis Pasini, Garassino and De Angeli, 2017 are herein recorded, together with some additional well-preserved specimens of the previously reported Albaidaplax ispalensis Garassino, Pasini and Castro, 2013 and Chlinocephalus demissifrons Ristori, 1886. A shark teeth assemblage related to whale fall events is here documented. Moreover, the common tracks of burrowing organisms, referable to activity of crustaceans and echinoids, have been documented, allowing to reconstruct the life on the shallow seabed (maximum depth of about 150m) of scavengers and opportunists, which developed around a whale carcass. The identification of a specialized community (biome) of benthonics and nectonics, contributes to best define this peculiar bioenvironment, confirming the development at Bargiano and Montemoro sites of the four Ecological stages (Scavengers, Opportunists, Sulphophilic and Reef stages) linked to the whale fall events.

Berger et al. – The endocranial anatomy of protocetids and its implications for early whale evolution.

Extant whales, dolphins, and porpoises result from a major macroevolutionary lifestyle transition that transformed land-dwelling cetaceans into fully aquatic species. This involved significant changes in sensory systems. The increase in brain size relative to body size (encephalization quotient) is an outstanding feature of modern cetaceans, especially toothed whales. Conversely, olfactory capabilities are assumed to have diminished along this transition, with airborne olfaction becoming less relevant. The extent and timing of olfactory reduction remain obscure due to challenges in accessing well-preserved fossil endocranial anatomy. This study shows that early cetaceans had already evolved an increased encephalization quotient, and that their olfactory apparatus was likely not yet under selective pressure leading to its reduction. We demonstrate this through an analysis of the extinct whale, Protocetus atavus, a member of the middle Eocene semiaquatic cetacean group Protocetidae. We provide the first documentation of its endocranial anatomy using high-resolution computed tomography and compare it to other early cetaceans as well as extant mammals. We conclude that cetaceans increased their brain size earlier than previously thought, while relying on a well-developed olfactory system at a time when they were still partly terrestrial.

Bisconti et al.– A new fossil from the Late Miocene of Piedmont (north-western Italy) sheds light on the evolution of the Cetotheriidae (Mammalia: Cetacea: Mysticeti).

The baleen-bearing whale Albacetus salvifactus gen. et sp. nov. from the upper Tortonian of Piedmont (north-west Italy) is described herein and compared to an extended sample of mysticete cetaceans. The new taxon belongs to the Cetotheriidae sensu stricto family-rank clade and is closely related to the genera Herentalia, Brandtocetus, Ciuciulea, Adicetus and Tranatocetus from the North Atlantic, Mediterranean and Paratethys basins. The computed tomography (CT) scan of Albacetus salvifactus revealed several previously undescribed characters including the neurovascular characters of the rostrum and the virtual skull endocast. Based on the CT scan, the periotic of A. salvifactus was three-dimensionally reconstructed. The skull endocast revealed that the encephalization quotient (EQ) of A. salvifactus is in the 95% confidence interval of the EQ variation in mysticete cetaceans. Some functional areas of the brain were reconstructed based on specific impressions on the endocast surface, likely corresponding to the sylvian, ectosylvian, suprasylvian and ectolateralis fissures. Phylogenetic analysis revealed that Cetotheriidae sensu stricto is subdivided into two subclades: (1) a North Atlantic group and (2) a widespread group including Herpetocetus, Piscobalaena, Metopocetus and Cetotherium. Phylogenetic results suggest multiple invasions of the Paratethys by different cetotheriid groups. Comparative phylogenetic analyses showed that the monophyly of Caperea and Cetotheriidae sensu stricto, the monophyly of Plicogulae and the monophyly of Tranatocetidae are less parsimonious than the solution proposed herein, thereby reinforcing the monophyly of Balaenoidea, Balaenopteroidea and Thalassotherii.

Remarks: This paper is really about quite a lot more than just the new whale Albacetus. Mysticete researchers will want to digest this in detail since the study includes a number of quite expansive 'meta' analyses of mysticete evolution, which is characteristic of Michelangelo's recent papers taking more of a birds eye view of things. It's really quite excellent.

Note: the skull is a reconstruction; the skeleton is headless.

Bisconti et al. – A new Pliocene sperm whale from Vigliano D'Asti, Piedemont, Northwest Italy.

A new sperm whale species is described from the late Zanclean (Early Pliocene) of Piedmont, northwest Italy, based on a partial vertebral column and parts of the forelimb. The new taxon, Eophyseter damarcoi gen. nov. sp. nov., is characterized by elongated vertebral centra in the thoracic and lumbar regions of the vertebral column, wider and higher articular facets for the occipital condyles in the atlas, elliptical and dorsoventrally compressed posterior articular facet of the axis-bearing block, ulna with posteriorly convex margin. These characters distinguish Eophyseter damarcoi gen. nov. sp. nov.from other physeteroids and show that the vertebral proportions are differently arranged with respect to those of the extant sperm whale species. A phylogenetic analysis was performed to understand the relationships of Eophyseter damarcoi gen. nov. sp. nov. by adding 20 postcranial characters to a previous character x taxon matrix; it revealed that E. damarcoi gen. nov. sp. nov. forms a clade with P. macrocephalus. A taphonomic analysis suggested that the carcass of the holotype specimen of Eophyseter damarcoi gen. nov. sp. nov. was exploited by sharks and colonized by barnacles and molluscs; however, a quick burial prevented its total destruction by other invertebrates, as usual in the cetacean fossil record from the Pliocene of Piedmont.

Bisconti et al. – Taphonomy and whale-fall analysis of the Tortonian baleen whales from the Stirone river, Emilia Romagna (northern Italy)

The taphonomy of three balaenopterid skeletons is examined in order to describe the traces left by whale fall communities. The whale specimens include two partial skeletons and an isolated periotic; one of the partial skeletons is the holotype of Plesiobalaenoptera quarantellii, while the other two specimens represent two indeterminate balaenopterid species. The high number of trace fossils observed in these specimens was not observed in previous paleontological records of whale fall communities. The diversity of the trace fossils and the broad stratigraphic context in which the assemblages are included are investigated in order to investigate into the origin and evolution of the specialized whale fall communities since the Neogene. Macrophotographs, three-dimensional modeling from photogrammetry and laser scanner examinations of the specimens were used to analyze the diversity of trace fossils observed on the bones of the balaenopterids. Biostratigraphic analyses of the outcrops where the specimens were discovered were realized to constrain the ages of the specimens and to reconstruct paleoecological characters of the sites. Additionally, analyses of fish otoliths, mollusc shells and microfossils were carried out to refine the ecological setting of the sites. The partially articulated skeletons were affected by intense bioerosion and disarticulation that displaced several bones before the final burials.Trace fossils found on the whale bones include shark bite traces, Trypanites, Gastrochaenolites, ?Meandropolydora and Gnatulichnus ichnogenera documenting an intense exploitation of the energy reservoir represented by these carcasses. The biostratigraphic analysis of the site supports a Late Miocene (Upper Tortonian) age and shows presence of post-depositional processes. These included micro-faulting that acted on the whale bones and, in one case, provided forces able to deform a lumbar vertebra. Fish otoliths, mollusc shells and microfossils are consistent in supporting a c. 100 m deep inner shelf deposit. Absence of chemoautothrophic molluscs from the present whale falls confirms that water depth may be the main determinant of the presence of these highly specialized species, that flourish in anoxic environments, because decomposition at shallow depths may still occur in presence of high Oxygen concentrations. Those described herein are the most dense ensembles of traces documenting whale falls communities in the Late Miocene described up to now.

Bouaziz et al.– Morphological study of the anterior dentition in Raoellidae (Mammalia, Artiodactyla), new insight on their dietary habits.

Raoellidae are small artiodactyls from the Indian subcontinent closely related to stem cetaceans. They bring crucial information to understand the early phase of the land-to-water transition in Cetacea. If they are considered to be partly aquatic, the question of their dietary habits remains partly understood due to their “transitional” morphology. Raoellidae are largely documented by their cheek teeth and getting a better knowledge of their anterior dentition constitutes an additional proxy to discuss their feeding habits. In this work, we document the anterior dentition of Indohyus indirae from an unprecedented sample of in situ and isolated teeth from the locality of East Aiji-2 in the Kalakot area (Rajouri district, India). We propose identification criteria for upper and lower incisors and canines in raoellids. Based on CT scan data, virtual reconstruction of in situ dentition, and identification of the isolated incisors and canines, we reconstruct a composite anterior dentition of Indohyus supported by the correspondence of wear facets between upper and lower teeth. This constitutes the first attempt at reconstruction of the anterior dentition of a raoellid. We show that the upper incisors are caniniform and very similar morphologically, whereas the lower incisors are pointed but remain incisiform and quite different from one another. We also describe noticeable intraspecific variation, at the level of upper canines, suggesting a potential sexual dimorphism in this species. Upper and lower incisors are recurved, with the upper incisor row arranged on a widely opened arch. Taken altogether the anterior dentition forms a grasping device, allowing the animal to capture and secure food, a characteristic shared with stem cetaceans. This would mark the first step towards the carnivorous diet in these peculiar artiodactyls.

Cedillo-Avila et al. - First record of an Eomysticetidae from the Late Oligocene at the Pilon locality, San Gregorio Formation, Baja California Sur, Mexico.

In the paleontological history of cetaceans, the group Chaeomysticeti represents the most basal lineage of baleen whales, as we know them today. Within this group, the family Eomysticetidae, which dates back to the Oligocene Epoch, has been identified in the Northern Hemisphere–specifically in the Pacific Ocean along the coasts of Japan and Mexico, as well as in the Atlantic Ocean in the United States. Additionally, fossils have been discovered in the Southern Hemisphere, particularly in New Zealand. In Baja California Sur, the discovery of Eomysticetidae fossils provides a more comprehensive record than previous findings and enhances our understanding of the relationship between the faunas of the Southern Hemisphere and those of the Northern Hemisphere. So far, one skull, two jaws and the left tympanic bulla have been uncovered, and the level of preservation is conducive to detailing important elements within the family, such as the temporal fossa, the intertemporal region, the length of the nasal bones and the secondary squamosal fossa, among others. Using phylogenetic tools such as TNT software, this anatomic evidence allows us to classify a new genus and species from the Oligocene Epoch.

Remarks: Another new eomysticetid! I was quite pleased to see this reported, and from Baja, no less! This is from the San Gregorio Formation, one of two major Oligocene cetacean bearing units in Baja (the other being the El Cien Formation, which you are going to be hearing about MUCH MORE in the coming months). Unfortunately, as is the case for many Oligocene cetaceans from the Pacific Northwest, indurated concretions that aren't soluble make for challenging prepwork - and as a result, the highly informative earbones remain in situ and virtually nothing is known of the periotic. The tympanic bulla has been removed, and it does have some unique features - though many other aspects of the skull remind me of Matapanui waihao, which I reported nearly a decade ago from New Zealand. The specimen is claimed to lack palatal sulci, though I think the preservation prohibits this observation as the foramina are quite narrow and the sulci quite short, so any surficial damage or fracturing can really obscure these features - and it's worth noting that in every eomysticetid with a well-preserved palate, the foramina are there (and, though the Oregonian eomysticetid Maiabalaena was claimed to lack them, CT data indicates the foramina are there, and fully acknowledged in the supplementary data of that study).

Davydenko etal. – A high-resolution 3D reconstructed skeleton of the extinct dwarf whale Cetotherium riabinini from Ukraine.

Cetotheres (family Cetotheriidae) were small-sized extinct baleen whales, likely the smallest among toothless baleen whales. Cetotherium riabinini Hofstein, 1948 is known as a single specimen, the holotype. It is represented by a well-preserved 3 meter long skeleton including an almost complete skull and most of the postcranial bones. This specimen is held in the National Museum of Natural History in Kyiv, and therefore it is the part of fragile Ukrainian heritage at risk. Thus, creating high resolution digital twins of the specimens serves not only for research purposes but also contributes to a partial preservation of heritage. Here we present a full-size 3D surface scan of the mounted skeleton of Cetotherium riabinini, a detailed scan of its right forelimb, and scans of its separately stored bones from the museum collection. Additionally, we provide a complete digital restoration of the C. riabinini skeleton, combining all available bones, reconstructing damaged elements, and modelling missing bones based on those in related baleen whale species both extinct and recent.

Ducrocq et al.– A partial skeleton of Metaxytherium medium from the middle Miocene of La Morfassière quarry (Indre-et-Loire, France)

Sirenians are among the common marine fossil remains found in the Faluns deposits of western France. We describe new material of a Dugongidae sirenian from the middle Miocene Savignean facies of La Morfassière quarry (Indre-et-Loire, northwestern France) that includes a well preserved and almost complete skull associated with its mandible, several vertebrae and ribs. The cranial remains exhibit features that allow to attribute them to Metaxytherium medium, a species recorded from the middle and early late Miocene of European and Mediterranean coasts. The discovery of an associated skull and mandible of this species is unusual in this area and deserves to be reported, mostly because its preservation contributes to a better knowledge of the variable structure of its skull and teeth anatomy. For the first time the body size and weight of M. medium can be assessed through regression equations based on skull measurements. The particularly good condition of the material can be explained by the calm and deep marine environment in which it was deposited.

Duncan et al. – An immature toothed mysticete from the Oligocene of Australia and insights into mammalodontid (Cetacea: Mysticeti) morphology, systematics, and ontogeny.

Mammalodontids are a clade of toothed mysticetes known only from the Chattian of south-eastern Australia and New Zealand. Despite three named species (Janjucetus hunderi, Mammalodon colliveri, and Mammalodon hakataramea), the majority of mammalodontid material, largely represented by isolated teeth and ear bones found within the Torquay Basin (Victoria, Australia), remains undescribed. Here we describe a new species of mammalodontid, Janjucetus dullardi sp. nov., from the Jan Juc Marl. The holotype was found stratigraphically lower than M. colliveri and has morphology consistent with an immature stage of growth, plus near-unworn dental morphology. We identify a correlation between occipital condyle breadth and bizygomatic width and propose equations that permit us to estimate bizygomatic width and, subsequently, a body size estimate similar to the smallest known toothed mysticetes of ∼2.05–2.18 m. Phylogenetic analysis recovers J. dullardi as sister to J. hunderi within a monophyletic mammalodontid clade in all analyses. It also provides support for Mammalodontidae within Mysticeti, sister to an Aetiocetidae + Chaeomysticeti clade. Finally, revised diagnoses of Mammalodon and Janjucetus incorporating newly recogniszed tympanic and periotic characters permit the identification of isolated ear bones and inference of ontogenetic variation within Janjucetus.

Remarks: This study reports a new fragmentary specimen of Janjucetus as part of Ruaridh Duncan's thesis research. The new specimen is a juvenile, and while it's far less spectacular than the holotype of Janjucetus hunderi (reported by Erich Fitzgerald in 2006), there's a lot of critical data packed into this paper, which approaches the density of a neutron star (this is a compliment coming from a student of Ewan Fordyce). Several other formerly unpublished mammalodontids are reported and figured in detail, new observations from the basicranium of Janjucetus hunderi are reported, and my low-key favorite - the missing part of the periotic of the Mammalodon colliveri holotype was reunited and re-figured and re-described here. In 2013 Erich Fitzgerald was looking through a sample bag of matrix in the museum collection, apparently unopened since the 1930s, and found the posterior process of the periotic, which clicked right on to the rest of the earbone. My guess is that the periotic was broken during collection and the fragment stuck into a sample bag and forgotten.

Farnkopf et al.– Cribriform plate size documents loss of olfactory receptor genes in the early evolution of whales, dolphins, and porpoises.

Having transitioned from a terrestrial lifestyle to an aquatic one over evolutionary time, cetaceans are prime subjects for the study of reduced olfaction. Here, we investigated the size of the cribriform plate in extant Artiodactyla and fossil whales. We also investigated the number of olfactory receptor (OR) genes encoded in artiodactyl genomes and found that the size of the cribriform plate is positively correlated with the number of OR genes among extant species. We extended this finding to fossil whales and estimated that a loss of genes occurred during the early/middle Eocene, before cetaceans became obligately aquatic. Extant toothed whales have reduced olfaction, but two Miocene toothed whales are predicted to have as many or more OR genes than extant baleen whales. Therefore, some fossil toothed whales might have had some olfaction. For their body size, extant baleen whales have cribriform plates that are similar in size to that of the dromedary camel, which is consistent with the growing evidence that baleen whales have retained some olfaction. As the first quantitative, morphological analysis of cetacean olfaction across the land-to-water transition, our study facilitates further study of olfactory neuroanatomy and the link between olfactory phenotype and genotype.

Furlanetto etal. – The first Miocene Osedax traces on a whale bone from the Northern Apennines, Italy

Large cetacean carcasses that sink to the bottom of the deep sea are usually colonised by a wide variety of organisms, forming the so-called whale fall communities. We studied a fragmentary long bone of an unidentified cetacean from the palaeontological collection of the Università di Modena e Reggio Emilia collected near Montegibbio (Modena, Italy). The dating of the associated sediments, by means of calcareous nannofossils, indicates a early-middle Tortonian age for the specimen, allowing us to assign it to the Termina Formation. The bone, which shows signs of bioerosion on the outer surface, was analysed using 3D photogrammetry and micro-CT scanning to characterise the external and internal shape of the fossil traces and to understand which organism produced them. Externally, the bone surface shows rounded to irregular pits, a few millimetres to four centimetres wide, where the compact bone has been removed exposing the underlying cancellous bone. Smaller pits are isolated, while larger ones merge. These surface traces are similar to those made by the bone-eating worm Osedax on modern marine vertebrates, a polychaete of the family Siboglinidae that uses a specialised root tissue to penetrate the bones from which it obtains nutrients via endosymbiotic, heterotrophic bacteria. However, only small cavities with a single hole reflect the shape of an individual animal’s root system and are of diagnostic value. Using digital segmentation of the scan slices, we isolated, measured and reconstructed the 3D morphology of single boreholes. We distinguished three distinct morphotypes and found similarities in size and shape with boreholes produced by modern Osedax species. Our findings, which represent the oldest fossil record of Osedax traces from the Mediterranean area, and the first Miocene record worldwide assessed via micro-CT scan images, are consistent with the presence of a high diversity of cetaceans in the Late Miocene proto-Mediterranean Sea.

Gaetan et al. – Echoes from the Miocene: tracing the anatomy and phylogeny of Prosqualodon australis (Cetacea: Odontoceti).

Odontocetes compose the most ecologically and taxonomically diverse clade of marine mammals. All modern odontocetes are homodont, but the early history of this group (Oligocene–Early Miocene) was dominated by a variety of bizarre forms with archaic features. Among these archaic odontocetes was Prosqualodon australis, a medium-sized, brevirostrine species from the Early Miocene of Patagonia (Argentina). It was originally described based on a partial skull; however, extensive fieldwork in Early Miocene outcrops in Patagonia has yielded several new specimens, including skulls with well-preserved basicranium, ear bones and postcranium. Based on this broad new sample we provide an updated anatomical description and phylogenetic analysis of P. australis and discuss other referred specimens to the species. We also perform a taxonomic revision of the other two species of the genus, P. davidis (Australia) and ‘P.’ hamiltoni (New Zealand). Our studies confirmed the phylogenetic position of P. australis as an early-diverging (i.e. stem) odontocete and add diagnostic characters from the basicranium and periotic to the already known features that define P. australis: presence of a triangular-shaped parafalciform fossa, and a narrow and deep furrow that originates from the periotic fossa and is anteromedially blind, periotic with a promontorial groove associated with an anteroventral tubercle and well-developed dorsal crest. Most anatomical differences between P. australis and the holotype of P. davidis are interpreted as ontogenetic variation, suggesting that P. davidis is a junior synonym of P. australis, making it the first circumpolar odontocete species from the Southern Hemisphere. Conversely, the anatomical and phylogenetic differences between P. australis and ‘P.’ hamiltoni suggest that these taxa are not congeneric. The results of our work provide, for the first time, a thorough anatomical and systematic revision of the genus Prosqualodon, focusing on P. australis, based on one of the most outstanding fossil odontocete samples.

Remarks: The sample reported in this study is simply amazing - seven partial to nearly complete skulls. In my 2023 monograph on Xenorophus, I lamented that paleocetology tends to focus on 'singletons' - limiting new descriptions to a single specimen. I've also complained about that problem before on this blog. This study takes the hypodigm approach and refers a ton of new specimens to Prosqualodon australis. This approach permitted the authors to assess ontogenetic changes within the species - and determine that Prosqualodon davidis from rocks of the same age in Tasmania - the only known specimen of which has been lost for over fifty years - is simply a young adult specimen of the same species, and they synonymize it with Prosqualodon australis. I suspect that with many other species known by multiple specimens, a greater apreciation of individual and ontogenetic variation will result in many similar synonymies being declared.

Ghazali et al.– Humerus shape evolved in cetaceans under relaxed selection and random drift

Mammalian humerus shape is mostly predicted by loading. This constraint is lifted for cetaceans and, therefore, can reflect other, specific evolutionary trends. To test this hypothesis, the three-dimensional shape of the humerus for 36 taxa of extinct and extant cetaceans was analyzed. The shape variance concurs with the evolution of diverging baleen and toothed whales and is independent of allometry. It shows traits associated with aquatic locomotion: humeral head twist, diaphysis shortening and straightening, and epiphyses enlargement. Also, changes in the anatomy of the humeral head and greater tubercle, modularity and integration patterns are associated with phylogeny. We suggest relaxed negative selection and random drift as the likely main evolutionary patterns for the evolution of the humerus shape. The evolution of genes regulating the humerus shape corresponds to the anatomical transformations and shows relaxed selection, site-level positive selection and nonsense mutations in cetaceans. Overall, the observed pattern well illustrates a “fly in a tube model” and shows its importance as a framework of emerging evolutionary innovations.

Godfrey et al. – New light on the trophic ecology of Carcharodon hastalis from teeth embedded in Miocene cetacean vertebrae from Calvert Cliffs in Maryland, USA.*

Recent isotopic analyses of the teeth of the extinct lamnid Carcharodon hastalis showed that it fed at a comparable trophic level as was the fossil and modern great white shark, Carcharodon carcharias. Although there are many examples of shark bite marks on marine mammal bones, there have not been any publications documenting the presence of C. hastalis teeth embedded in the bones of marine mammals. Here we report on the first C. hastalis teeth found embedded in vertebrae of two Miocene cetaceans. These teeth represent unequivocal evidence of trophic interactions between this shark and cetaceans. It is not known if these interactions were the result of active predation or scavenging. These embedded C. hastalis teeth offer supporting evidence to the aforementioned isotopic findings. The finding of C. hastalis teeth embedded in cetacean vertebrae demonstrate that in the Carcharodon lineage, serrated teeth were not a prerequisite to feeding on marine mammals. Carcharodon hastalis may have fed on marine mammals for millions of years prior to the evolution of lightly serrated teeth in its chronospecific descendent, Carcharodon hubbelli. The behavioral adaptation to mammalophagy in the Carcharodon lineage, regardless as to how inefficient it might have been without serrated teeth, appears to have occurred for millions of years prior to the evolution of fully serrated teeth in Carcharodon carcharias. That feeding behavior may well have given natural selection sufficient time to develop and hone the serrated teeth now seen in extant great white sharks (C. carcharias). Given that competition for high trophic resources between the Carcharodon and Otodus lineages seemingly existed for millions of years prior to the extinction of Otodus megalodon, it seems that competition alone is likely not the only explanation for why O. megalodon went extinct.

Hernandez-Cisneros and Velez-Juarbe – Morphology of the toothed mysticete Fucaia goedertorum and a reassessment of Aetiocetidae (Cetacea, Mysticeti).

Aetiocetids are a relatively diverse group of small toothed mysticetes that lived from the late Eocene through the late Oligocene in the North Pacific Ocean. They are characterized by a combination of morphological features that places them between earlier mysticetes (e.g., mammalodontids) and chaeomysticetes. Since the first aetiocetid was described in the 1960s, their significance in understanding mysticete evolution has been broadly discussed, with particular attention to aspects of their paleobiology (i.e., feeding strategies). However, morphological features that could offer additional insight into their paleobiology, like the tympanoperiotic complex, dentition, and postcranial elements, are still poorly understood due to incomplete specimens or partial descriptions. In this context, this study provides a detailed description of Fucaia goedertorum (LACM 131146), which represents one of the most completely preserved aetiocetid specimens, thus allowing for a better understanding of the cranial and postcranial morphology of this group. The craniomandibular and postcranial morphology of Fucaia goedertorum displays a unique combination of plesiomorphic and derived characters, such as proportionately large orbits, presence of upper and lower teeth, well-defined embrasure pits, a kinetic mandibular symphysis, multi-element sternum, flexible vertebral column and proportionately long flippers, among others. Our interpretations of the cranial and postcranial morphology of Fucaia goedertorum, suggest that it was a raptorial or suction-assisted raptorial feeder with high flexibility and maneuverability, more akin to what is observed in otariids. Combined with current interpretations proposed for other aetiocetids, we suggest that this group of early mysticetes displayed a broad range of feeding strategies.

Remarks: I've been waiting for the eventual longer format description of this little toothed baleen whale since I began my Ph.D. research in 2012. A half dozen species of aetiocetids were all named in a single paper in 1995, and the well-preserved and well-prepared Chonecetus goedertorum (later reassigned to the new genus Fucaia) was certainly the 'flagship' specimen of the paper, with the longest description - some of the other species had descriptions only a few paragraphs in length. Longer descriptions were promised, but never delivered. In 2008, another team revealed that Aetiocetus weltoni had palatal foramina likely homologous with those in modern baleen whales, suggesting that it had teeth and baleen. A longer description of Aetiocetus weltoni was published the same year. Seventeen years later, we now have a similar treatment of Fucaia goedertorum.

Jackson et al. – An annotated checklist of Australasian fossil mammals.

Australasia has had a rich history of discovery of fossil mammals, with the first specimens collected within Wellington Caves, New South Wales and described by Richard Owen in 1838. Currently, a total of 482 fossil mammal taxa are recognized from the Australasian region including: 406 from Australia; 33 from Indonesia incorporating the islands of Alor, Aru, Flores, Morotai, Sulawesi, Sumba, West Timor, and western New Guinea; two from Timor-Leste; 14 from Papua New Guinea; and 27 from New Zealand. Of the fossil mammal taxa described, 23 are extant and eight are recently extinct. Although the relationships between many fossil mammal groups are becoming increasingly clear, there are still many gaps in the fossil record, and numerous uncertain phylogenetic relationships that need to be resolved. This review for the Australian Fossil National Species List syntheses current knowledge of Australasian fossil mammals, which will undoubtedly be revised substantially in the future as new discoveries are made.

Jamison-Todd etal. – The earliest fossil cetacean with Osedax borings: narrowing the spatiotemporal gap between Cretaceous marine reptiles and late Cenozoic whales.

Borings of the extant bone-eating worm Osedax have previously been found in Cenozoic cetaceans and Cretaceous marine reptiles. The stratigraphically youngest Cretaceous example is from the Maastrichtian, and, until now, the oldest Cenozoic example was from the Oligocene. This leaves a substantial temporal and taxonomic gap between examples from both Osedax-hosting tetrapod groups. Here, we report nine fossil cetacean specimens with Osspecus (Osedax bioerosion), identified via CT scans. These include a late Eocene occurrence of the basilosaurid Zyghorhiza kochii from the eastern USA, which represents the earliest known Cenozoic occurrence of Osedax borings, narrowing the temporal gap between occurrences of Osspecus in Cretaceous marine reptiles and Cenozoic whales. These specimens also include the first Osspecus-bearing fossil cetaceans from the northwestern Atlantic, expanding the Cenozoic biogeography of Osedax. Six ichnospecies of Osspecus are found in these cetacean fossils, including one newly described ichnospecies. The high morphological diversity of Osspecus in these Cenozoic specimens is broadly consistent with that of the Late Cretaceous, with several ichnospecies now known from both time intervals. Surviving lineages of other large marine vertebrates, such as turtles, crocodyliforms and fish, likely acted as suitable resources for Osedax across the Cretaceous–Paleogene boundary, bridging both the temporal and taxonomic gap.

Remarks: An interesting study - but fails to cite work I did ten years ago on Osedax traces on Oligocene eomysticetids from New Zealand with Ewan Fordyce.

Kimura andNishioka – A baleen whale fossil from the Upper Miocene Sagara Group, Omaezaki, Shizuoka Prefecture, Japan.

We describe a tympanic bulla of a baleen whale from the Upper Miocene Sagara Group, Shizuoka Prefecture, Japan. The geologic age of the Sagara Group has been correlated to N16-17 (ca. 9-6 Ma) of Blow's number by the planktonic foraminiferal biozone. The specimen consists of a fragment of left tympanic bulla. It exhibits a following combination of morphological characters, and here we describe this specimen as an unidentified fossil species of Plicogulae: the absence of an apparent interprominential notch and the lack of dorsoventral compression of the bulla. Only a few cetacean fossils have been reported from Shizuoka Prefecture, and this is the first formally described cetacean fossil from the Sagara Group.

Kimura and Takakuwa – A new specimen of Kentriodon nakajimai from the Haraichi Formation (Annaka Group) of Takasaki City, Gunma Prefecture, Japan.

We describe a new specimen of Kentriodon nakajimai, which was recovered from the lowermost Upper Miocene Haraichi Formation, Annaka Group of Takasaki, Gunma Prefecture, Japan. The specimen consists of a partial cranium and is referred to Kentriodon nakajimai based on the following combination of morphological characters: enlarged fossa for the preorbital lobe of the pterygoid sinus; well developed right maxillary crest; deep antorbital notch; the fossa for the pterygoid sinus is elongated far anterior to the level of the antorbital notch, and the shape of its anterior end is pointed rather than rounded; the lateral edge of the premaxilla posterior to the level of the premaxillary fossa is nearly straight rather than convexly curved; the outline of the nasal bone is triangular in dorsal view; and the frontal extends anteriorly between the nasals. This specimen is the eighth individual of Kentriodon nakajimai formally described from the Haraichi Formation.

Lambert et al.– A tiny dolphin (Cetacea, Odontoceti, Kentriodontidae) cranium from the Middle Miocene of the southern North Sea with a rare osteological malformation.

Though the Neogene deposits of northern Belgium yielded many marine vertebrate remains, including cetaceans, the fossil record of several clades remains scarce. Among echolocating toothed whales (Odontoceti), cranial fossils of early delphinidans generally referred to the family Kentriodontidae are surprisingly rare in the Miocene units of the Antwerp area. Recently, a large construction pit excavated in the city centre of Antwerp allowed for the lithostratigraphic description of a section in the Kiel and Antwerpen members of the Berchem Formation. In addition to an elasmobranch assemblage of 13 species, a well-preserved, tiny odontocete cranium was discovered in the lower part of the Antwerpen Member (Middle Miocene, lower Langhian). Representing a young individual, this rare fossil displays strong anatomical similarities with the small kentriodontid Kentriodon pernix, originally found in upper Lower to Middle Miocene deposits of the Atlantic Coastal Plain (USA). It is referred here to Kentriodon cf. K. pernix, contributing to the improvement of the scant fossil record of early delphinidans in the North Sea. Associated to a degree of tooth wear that is unexpected in such a young individual, highly unusual anatomical traits, especially in the orbit region, are interpreted as resulting from a malformation that occurred relatively early during cranial development.

Lambert et al. – New data on archaic homodont odontocetes from the Early Miocene of Peru reveal a second species of Chilcacetus Lambert, Muizon & Bianucci, 2015 and a Southern Hemisphere record for a northeastern Pacific species.

The systematic affinities of several homodont odontocetes (toothed whales) in the genera Argyrocetus Lydekker, 1893 and Macrodelphinus Wilson, 1935 from the Early Miocene of the northeastern Pacific and southwestern Atlantic have long been debated. The description of the longirostrine dolphin Chilcacetus cavirhinus Lambert, Muizon & Bianucci, 2015, based on two finely preserved skulls from the Early Miocene of Peru, revealed similarities with part of these taxa, but questions remained about their phylogenetic relationships. Two new specimens from the Burdigalian of the Chilcatay Formation (East Pisco Basin, Peru) and recently rediscovered skull parts for the holotype of C. cavirhinus lead to the diagnosis of a new species of Chilcacetus Lambert, de Muizon & Bianucci, 2015, Chilcacetus ullujayensis n. sp., and the description of cranial regions previously unknown (or poorly known) for that genus, especially the ear bones. Another smaller skull from the Chilcatay Formation is referred here to Amphidelphis bakersfieldensis n. comb., a species previously only known from California whose palaeogeographic distribution is thus expanded across the equator. Rostral morphological features in the new specimen of A. bakersfieldensis n. comb. differ markedly from Argyrocetus patagonicus Lydekker, 1893, the Patagonian species that was earlier recognized as closely related to A. bakersfieldensis n. comb., and from Eurhinodelphinidae Abel, 1901, the family long proposed to have housed these two species. Finally, two other specimens from the Chilcatay Formation are identified as Odontoceti aff. A. bakersfieldensis. New phylogenetic analyses recover Chilcacetus spp. and A. bakersfieldensis n. comb. in a clade of longirostrine to hyper-longirostrine stem odontocetes, also including Eoplatanista Dal Piaz, 1916, Macrodelphinus, and eurhinodelphinids. The new records of A. bakersfieldensis n. comb. and Chilcacetus spp. presented here confirm the predominance of long-snouted species in the Burdigalian odontocete assemblages of the East Pisco Basin.

Remarks: This study is a nice follow-up to an earlier 2015 study on the early odontocete Chilcacetus, which belongs to a poorly understood clade of odontocetes near the base of the crown clade with many skull features similar to the Eurhinodelphinidae. I'm of course pleased that they name a new genus, Amphidelphis, for a Californian fossil, formerly known as "Argyrocetus" bakersfieldiensis. Perhaps one of my favorite aspects of this paper, however, is the rediscovery of lost parts of the rostrum and mandible of the holotype of Chilcacetus cavirhinus; these elements, along with the earbones, were lost at some stage between collection and publication in 2015. Though the earbones still remain AWOL, the rostrum and mandible were re-attached to the holotype skull; these new skull parts indicate that the rostrum did not protrude beyond the end of the mandible as it does in the strange eurhinodelphinids.

Lazarev et al.– Hydrological isolation of the Paratethys in the late Middle-Late Miocene: integrated stratigraphy, palaeoenvironments and biotic record of the Caspian Basin, Karagiye, Kazakhstan.

The hydrological connectivity of semi-isolated basins with the global ocean drives remarkable ecosystem turnover and regional climate shifts, making palaeoenvironmental and palaeohydrological studies of the epicontinental basins of high relevance. During the late Middle–Late Miocene, the Paratethys Sea, which occupied vast areas of the West Eurasian Interior, underwent a notable hydrological isolation from the global ocean. Between 12.65 and 7.65 Ma, the Paratethys experienced significant water level fluctuations and eventually near-total ecosystem collapse. The causes and timing of these hydrological and biotic changes remain unclear, especially in the understudied Caspian Sea region. Our study presents an integrated stratigraphic framework of the 136-m-thick Karagiye section on the east coast of the Caspian Sea (Mangystau region, Kazakhstan). The fauna-rich deposits document the pre- (Konkian), syn- (Volhynian, Bessarabian and Khersonian) and post-isolation (Maeotian) phases of Paratethys evolution at its eastern margin. We reconstruct the palaeoenvironmental history of the Caspian Basin by combining palaeomagnetic dating with biostratigraphic analyses of microfauna, molluscs, marine vertebrates and calcareous nannoplankton. Our key findings in the studied section include: 1. Konkian (incomplete): Open lagoonal environments with restricted connectivity to the global ocean in the early Konkian followed by a middle Konkian faunal influx and establishment of normal marine environments; 2. Volhynian (incomplete, 12.3–12.05 Ma): Onset of Paratethys hydrological isolation with marginal lagoonal environments, new endemic species, plus rare surviving Konkian taxa; 3. Bessarabian (12.05–9.9 Ma): Transgression and offshore setting at ∼12.05 Ma with maximum flooding at 11.6 Ma and Intra-Bessarabian Carbonate Surge at ∼10.7 Ma, followed by upper Bessarabian (10.7–9.9 Ma) carbonate platform interior settings; 4. Khersonian (9.9–7.65 Ma): Khersonian Ecological Crisis, carbonate platform to backshore environments with hiatus between 9.5 and ∼8.0 Ma representing an extreme lowstand. 5. Maeotian (incomplete 7.65–7.0 Ma): Transgression at 7.65 Ma, followed by a delayed invasion of Maeotian faunas at 7.5 Ma, linked to the reconnection of the Caspian Basin with the rest of the Eastern Paratethys. The well-dated biotic record of Karagiye enhances understanding of Paratethyan hydrological and ecological events in the Caspian Basin and provides a foundation for further palaeoclimatic and palaeobiogeographic studies across Eurasia.

Marx andCampbell – First record of the Eocene baleen whale Llanocetus outside Antarctica.

Baleen whales (mysticetes) diverged from toothed whales and dolphins around 36 Ma. Among the oldest fossils attesting to their origin is Llanocetus denticrenatus from the Eocene (ca. 34 Ma) of Seymour Island, Antarctica. Isolated teeth from the same area suggest the presence of a second, potentially much larger species, but no further material of either form has been found to date. Here, we report the first record of Llanocetus outside Antarctica, based on a fragmentary but highly diagnostic tooth from Chatham Island, New Zealand. The new find considerably broadens both the geographical and the latitudinal range of the genus and suggests caution in interpreting the interrelationships of the basalmost mysticetes.

Nelson et al. – Redescription of the Late Oligocene heterodont odontocete Eosqualodon langewieschei from the historic Doberg of Bünde, Germany.

The fossil record of the late Oligocene, spanning from 27 to 23 Ma, bears evidence of the first major burst of diversification of crown Cetacea. The discovery of new species is crucial to understanding the full picture of this diversification burst, but review of poorly studied taxa is necessary as well. One such neglected taxon is Eosqualodon, a member of the heterodont odontocete family Squalodontidae, whose taxonomy has been neglected for decades. Here we examine the Chattian age (∼27 Ma) type species of Eosqualodon from north-western Germany. Represented by a complete skull and mandible, Eosqualodon langewieschei has historically received neither sufficient diagnosis nor description. Our redescription demonstrates E. langewieschei clearly bears diagnostic traits of the Squalodontidae, which include the robust, procumbent incisors and posterior teeth with crenulated and nodular enamel; this interpretation is supported by our phylogenetic analysis. However, our comparisons with species of Squalodon demonstrate that E. langewieschei is distinct from Squalodon and thus that the genus Eosqualodon is valid. Contrary to the taxonomy of previous workers, our phylogenetic analysis failed to capture a sister relationship between E. langewieschei and Eosqualodon latirostris, leading us to consider this genus to be monotypic, pending the revision of E. latirostris. Eosqualodon langewieschei possesses an enlarged temporal fossa, a dorsoventrally tall coronoid process of the mandible and a fossa on the coronoid ramus for jaw adductor musculature; these observations point to a macrophagous feeding strategy much like another late Oligocene odontocete, Ankylorhiza.

Nelson et al. – Taxonomic revision of the family Squalodontidae (Cetacea, Odontoceti): emptying the wastebasket of fragmentary holotypes.*

The Squalodontidae are one of the most historic families within the Cetacea, given that Squalodon was first named in 1840. Since Squalodon's initial description, workers in the 1800s were eager to assign heterodont cetacean teeth to this family; as a result, it became a wastebasket with many species based on fragmentary remains. Taxa represented by well-preserved specimens demonstrate that the Squalodontidae possess a mixture of ancestral and derived traits: they exhibit polydonty as most modern odontocetes do, but their teeth are still differentiated into incisor, canine and molariform types. Despite their position as a transitional form, the Squalodontidae have been neglected in the scientific literature and much of this is due to their poorly resolved taxonomy. While revisional work has been done for the North American record, the European record has remained a wastebasket. We assess here the taxonomic status of the 22 species in two squalodontid genera recorded from Europe spanning from the Chattian to the Serravallian. Both species of Eosqualodon bear diagnostic name-bearing specimens. However, of the 20 species of Squalodon, only six bear diagnostic types, and of those, one is a junior synonym. Our literature review of historic papers shows that the other 14 species of Squalodon have non-diagnostic name-bearing types, are synonymous with other species of Squalodon, or never had a specimen associated with the name. We also call into question the assertion that the Squalodontidae persist into the Serravallian, given that the youngest family-diagnostic specimens are found in units straddling the Langhian–Serravallian boundary.

Nelson et al. – Reassessment of the iconic Oligo-Miocene heterodont dolphin Squalodon: a redescription of the type species S. grateloupii.

Since its description in 1840, the toothed whale Squalodon was conceptualized as a transitional form between archaeocetes-like Basilosaurus and the modern toothed whales (Odontoceti). The cranial morphology of Squalodon approximates that of modern odontocetes; however, their dental patterning more closely resembles that of archaeocetes. Despite representing a transitional form, the Squalodontidae have been neglected in scientific study. The poor taxonomy of the family is the primary cause: significant specimens have not been redescribed, including the type species, S. grateloupii. Complicating matters, the holotype of that species has been missing for over a century, and this calls for the designation of a neotype by the ICZN. We present a neotype for S. grateloupii and synapomorphies for the genus and family, which include several features in the posterior basicranium and the periotic; we identified a strongly conserved dental pattern for the Squalodontidae. Given that the Squalodontidae has been underrepresented in phylogenetic analyses, our analysis included representatives from nearly all clades within Odontoceti, as well as every squalodontid species. Our results demonstrate that the Squalodontidae is monophyletic; unlike previous iterations of this phylogenetic analysis, the Squalodontidae were not recovered in crown Odontoceti. This result supports the hypothesis that homodonty is a synapomorphy of crown Odontoceti and did not evolve convergently, which is supported by four dental synapomorphies for crown odontocetes. Our modern revision of the iconic Squalodon lays the foundation for research into interspecies variation, ontogeny and biogeography of a key transitional form, so that we better understand the course of odontocete evolution.

Nobile et al. – Surviving a Dark Age: The Oldest Baleen-Bearing Whales (Cetacea: Chaeomysticeti) of Pacific South America (Lower Miocene, Peru).

The evolution of baleen whales (Mysticeti) comprises two main phases, namely, (i) a Paleogene phase, which saw the diversification of stem lineages, and (ii) a Neogene phase, dominated by modern-looking, toothless, baleen-bearing forms in the monophyletic group Chaeomysticeti. These two phases are separated by a global turnover event coinciding with a gap—or “dark age”—in the mysticete fossil record. This dark age occurred between 23 and ~18 Ma and is apparently detected worldwide, except in Zealandia. Here, we report on a new mysticete fossil from the Lower Miocene (Burdigalian: ~19.2 Ma) strata of the Chilcatay Formation cropping out at the newly discovered locality of Cerro Tiza (East Pisco Basin, Peru), which represents a limited but precious testament from the last phase of the baleen whale dark age. Two previously mentioned, slightly geologically younger fossils from the same formation are also reappraised herein, revealing the occurrence of at least another baleen whale taxon in the upper Chilcatay strata—one that belongs in the mysticete crown group. Although the Early Miocene remains a problematic time interval for the fossil record of baleen whales, our new results encourage the search for mysticete fossils in the Lower Miocene strata of the East Pisco Basin, whose basin fill preserves a cornucopia of extraordinarily informative marine vertebrate fossils of the Cenozoic age, as well as in coeval deposits worldwide.

Otriazhyi etal. – A new seal from the Late Miocene of the Eastern Paratethys highlights the past regional diversity of true seals (Phocidae).

True seals rapidly evolved in many forms in the epicontinental basin of Paratethys during the Miocene. However, most of their nominal taxa so far were proposed based on isolated limb bones, and their taxonomy has long been under discussion. Here we describe a new articulated skeleton MCFFM V-150 of a medium-sized seal with pachyosteosclerotic postcranial bones from the Late Miocene of the present-day Moldova and propose a new genus and species for it—Paratethyphoca libera. It is distinguished in the presence of a supraorbital process of the frontal bone in its posterior portion, a long snout, a proportionally long humerus (88% of the skull length), a short deltoid crest of the humerus, and a low supraspinatus fossa of the scapula. We also suggest this taxonomic identification for other Paratethyan seals. Phylogenetic analysis placed Paratethyphoca libera among other stem Phocinae described so far from the Paratethys; however, its close relationship to a living hooded seal Cystophora cristata cannot be ruled out. Additionally, MCFFM V-150 showed tooth wear interpreted as a sign of suction prey capture strategy, shared by another Paratethyan seal Monachopsis pontica and the living bearded seal Erignathus barbatus.

Otriazhyi etal. – The Miocene seal Monachopsis pontica: isolated in a shrinking sea and adapting to its changing conditions.

More than 170 years have passed since the description of the dwarf Miocene seal Monachopsis pontica. However, its cranial materials were rarely found and described. This paper re-describes M. pontica and discusses its ecological adaptations. M. pontica is among the latest seals that survived in the epicontinental sea Eastern Paratethys during the Khersonian biotic crisis. Newly examined materials from Ukraine, being exceptional in their completeness, show previously unknown traits of its morphology, unique among subfamily Phocinae. M. pontica is distinguished by its small body size (85–105 cm long), long snout and long deltoid crest of the humerus. Dental morphology shows that M. pontica was using raptorial methods of catching prey. However, the pattern of tooth wear also indicates suction feeding. The unusually small body size could be interpreted as a result of the decreasing size of the basin and the absence of predators. High crests on limb bones show evidence of the development of musculature driven by pachyosclerosis of the skeleton. Phylogenetic analysis placed M. pontica at the base of the crown Phocinae, crownward to the most known Miocene seals.

Ouilapan et al. – A Review of Cetacean Fossils from the Holocene Gulf of Ayutthaya.

Cetacean fossils from the Thai Lower Central Plains, or what was once the paleo-Gulf of Ayutthaya during the Holocene maximum transgression, despite their potential in the study of sea-level oscillations and their vast discoveries in the past centuries, have only been infrequently reported and lacked compilations, preventing insights into these past Cetacean faunas from being studied in the scientific field. Accordingly, this research aims to review the records of Cetacean fossils from the Holocene Gulf of Ayutthaya, experimentally retrace historical sea level transgressions using these fossils, and lastly, due to the diverse Cetacean record, to compare Holocene Cetacean faunas with present-day faunas of the Gulf of Thailand. Results showed that a total of 17 Cetacean fossil sites had been identified from the Thai Lower Central Plains, all being found in the Bangkok Clay Formation and dating from 1,000 to 6,000 YBP. The most abundant species found was Balaenoptera edeni (n = 7), out of the seven taxa discovered, and a specimen from Bang Khun Thian District, Bangkok is preliminarily reidentified as Ziphius cf. cavirostris, posing a new record of the genus in the Gulf of Thailand. Moreover, these Cetacean fossil localities also allow for an interpretation of the paleo-shoreline, being in line with previous research using different indicators, further solidifying the vast extent of the Holocene Gulf of Ayutthaya. Lastly, almost all of the Cetacean faunas identified are still present in the present-day Gulf of Thailand presenting the possibility that the faunas of the Gulf of Thailand could be descendants of the original population in the paleo-Gulf of Ayutthaya.

Paolucci et al.– Awakening Patagonia’s sleeping sperm whale: a new description of the Early Miocene Idiorophus patagonicus (Odontoceti, Physeteroidea).*

Idiorophus patagonicus is one of the oldest extinct sperm whales known, and was recovered from the Early Miocene Gaiman Formation (Chubut, Argentina). It was described in the late 19^th century by Lydekker based on an incomplete skull and has not been reviewed since its original description. Thus, many of its key anatomical features remain unknown, preventing a better understanding of the evolutionary trends in Physeteroidea. Here, we shed light on the anatomical features of Idiorophus patagonicus, its phylogenetic relationships and the palaeobiological aspects of its body size and feeding methods. Phylogenetically, Idiorophus is recovered as the basalmost member of the Physeteridae, or as a stem physeteroid; the most crownward physeteroid known from Patagonia. Idiorophus is a longirostrine species with a peculiar rostrum: it has a shape like the neck of a wine bottle, is tube like, and has the left premaxilla overhanging the right one, suggesting a structural advantage as a reinforcement of the rostrum from external pressures. Idiorophus is also a novelty in the evolution of sperm whale body size, being the oldest physeteroid (Burdigalian) with a large body size (6.61 m). The body size, skull morphology and the teeth wear facet of Idiorophus suggest a raptorial feeding method, which differs markedly from those inferred for the other Miocene Patagonian sperm whales (Diaphorocetus poucheti and Cozzuoliphyseter), suggesting a high ecomorphological disparity of the Patagonian sperm whale assemblage.

Park et al. – Functional trade-offs and innovation shape the adaptive landscape of aquatic mammal feeding.

Functional trade-offs are inherent in phenotypes due to the need to balance multiple competing selection pressures. Traditionally regarded as constraints on evolution, trade-offs have recently been reframed as facilitators of adaptation via the changing relative importance of competing functions. Here, we examine these ideas through the lens of aquatic mammal feeding, testing a behavioral aquatic feeding framework where feeding strategies form an evolutionary continuum from terrestrial to increasingly more specialized water-based feeding styles. Specifically, we hypothesized that suction, suction filter, and ram filter feeding would have adaptive peaks closer together than raptorial feeding, and that taxa follow the functionally optimal evolutionary path (Pareto front) between adaptive peaks. Constructing morphofunctional adaptive landscapes from cetacean mandibles revealed strong support for this framework. Surprisingly, most cetaceans do not lie along the Pareto front between peaks, suggesting that novel functional innovations— most likely the specialized cetacean auditory pathway—are also influencing mandibular evolution.

Paul and Larramendi – Further trimming down the marine heavyweights: Perucetus colossus did not come close to, much less exceed, the tonnage of blue whales, and the latter are not ultra-sized either.

Extrapolating from skeletal/total mass ratios, the gigantic Paleogene whale Perucetus colossus has been estimated to have massed 85 to 341 tonnes, approaching and even exceeding the blue whale (Balaenoptera musculus). Such a large variation in body mass lacks the precision needed for analytical accuracy and is therefore not of technical value. Despite sufficient remains for a much more accurate volumetric model, none was produced for robust testing their procedure. A subsequent paper downscaled Perucetus to 60 to 70 tonnes as the most probable estimate. To better assess the question, we have produced multiview profile-skeletals for Perucetus and other large marine mammals in the most extensive such effort to date. These include the first accurate restorations of a number of large marine mammals. Perucetus is restored using the proportions of heavy boned pachycetine basilosaurs. Cross comparisons and attempts to illustrate the extinct whale's realistic volume leave no doubt that the Perucetus holotype did not reach the cetacean heavyweight category. A length of 15 to 16 m and a mass of 35 to 40 tonnes is more in line with its known anatomy. This result was affirmed by recalculations of skeletal/total mass relationships in large pachyosteosclerotic marine mammals, which suggest the method can produce useful estimates if conducted properly. Although their initial size expansion was remarkably rapid, basal cetaceans did not balloon to super whale dimensions just a few million years after the initial evolution of the fully marine forms. Evolution of extremely large body size exceeding 50 tonnes did not occur until the late Neogene. The biggest whale of all time, the blue, is not likely to exceed ~30 m and 200 tonnes. It is emphasized that anatomical knowledge translated into technical volumetric models remains the most critical means of restoring the mass of extinct organisms.

Remarks: I have a review of this topic in a draft for an upcoming blog post. I generally find the uproar over the exact size of Perucetus to be a bit excessive... and the idea that blue whales aren't 'ultra sized' is a bit silly (since, you know, nothing else is larger).

Peacock et al.– The evolution of hearing and brain size in Eocene whales

Toothed whales (odontocetes) make use of high-frequency sounds to echolocate, differing significantly from their sister group baleen whales (mysticetes), which make use of low-frequency sound for long-distance communication. This divergence in auditory ability has led to considerable speculation as to how hearing functioned in the ancestral archaeocetes, and when the specializations of modern species arose. Numerous studies have attempted to infer auditory capabilities from morphological correlates valid in modern species. Here, we build upon these previous methods with a focus on cochlear structures that have well-understood links to function. We combine this with information on the sound conduction apparatus to chart the evolutionary trajectory of cetacean hearing. Our results suggest an initial move toward low-frequency specialization in early Eocene cetaceans, which coincides with the appearance of new sound conduction pathways. This paved the way for the later movement toward higher-frequency hearing in protocetids; however, the ultra-high- and low-frequency hearing specializations of both modern cetacean clades evolved after their divergence. We use these data to test the hypotheses that evolutionary brain size increases in cetaceans were related to the origin of high-frequency echolocation. We show that no shift in relative brain size coincides with any changes toward high-frequency perception. However, this does not rule out a role for other changes in hearing ability such as some simple forms of echolocation, similar to that suggested for hippopotamuses or bowhead whales, which may have been present in even the earliest cetaceans.

Remarks: I was actually quite shocked by the findings of this paper! It's been proposed, and assumed, for years that the large brains of toothed whales are unique to that group, and that they evolved as a result of requiring more brain matter to interpret the sounds used in echolocation. In this study, they determined that basilosaurid whales actually have considerably increased brain mass (relative to body mass) over prior archaeocetes, well within the range of modern mysticetes and some of the smaller-brained odontocetes. Brain size increase at the evolution of the basilosaurids (e.g. base of the clade Pelagiceti) does correspond to the evolution of acoustically isolated inner ears and therefore directional hearing - and not at the evolution of high frequency hearing within odontocetes. There is another brain size increase that occurs within the delphinoid odontocetes (delphinids, porpoises, and white whales) which does not seem to be associated with any change in hearing ability, and may instead (my speculation) be related to social behavior.

Pimiento et al.– Ocean Giants Through Time: Evolution and Ecology Intertwined.

Throughout geological time, an intertwined relationship between ecology and evolution has enabled distant clades to attain gigantism. By synthesizing fossil and modern data, we identify key tipping points in the rise of extreme-sized ocean animals—from early Cambrian arthropods and Ordovician mollusks to Triassic ichthyosaurs, Neogene sharks, and Quaternary whales. We show that ecological opportunities—from vacant niches to shifts in ocean productivity—have promoted the evolution of key adaptations to enhance prey intake, such as predatory appendages, specialized dentition, and baleens, ultimately enabling species to reach extreme sizes. The presence of ocean giants, in turn, has reshaped marine food webs, energy flow, nutrient cycling, and overall ecosystem structure. As such, their extinction or decline can have profound and lasting ecological consequences. Understanding the coevolutionary dynamics between marine giants and their environments is essential for predicting their resilience and conserving their critical roles in ocean ecosystems.

Post et al. - A new longirostrine beaked whale Flandriacetus gijseni gen. et sp. nov. (Ziphiidae, Cetacea, Mammalia) from the Tortonian of the North Sea Basin.

Based on 13 more or less complete skulls and some attached postcranial elements the presence of a new longirostrine beaked whale species Flandriacetus gijseni gen. et sp. nov. is reported from the southern North Sea Basin. Dated by dinoflagellate cysts to 8.1-7.5 Ma (Tortonian age), the new species represents the youngest occurrence of a longirostrine stem beaked whale in the North Atlantic. The large collection allows observations on the morphological differences between some of the North European members of the Messapicetiformes clade.

Pyenson et al. - High abundance of Early Miocene sea cows from Qatar shows repeated evolution of seagrass ecosystem engineers in Eastern Tethys.

Coastal ecosystems that include seagrasses are potential carbon sinks that require strategic conservation of top trophic consumers, such as dugongs, to maintain their function. It is unclear, however, how long seagrass ecosystems have persisted in geologic time because their fossil record is poor, although the record of their associated vertebrate consumers offers useful proxies. Here we describe an area of dense Early Miocene dugongid remains from Qatar. We documented over 172 sites in <1 km² from one stratigraphic level, including material representing a new species of fossil dugongine dugongid. This taxon is unrelated to coeval Early Miocene dugongids from India and the Eastern Tethys and it is distantly related to extant dugongs, which occupy seagrass habitats of the Persian or Arabian Gulf (hereafter ‘Gulf’) today. The monodominant assemblage in this area likely reflects a single fossil dugongid taxon and matches the ecological diversity and geospatial distribution of modern-day live-dead assemblages in the Gulf. This fossil site from Qatar shows that the Gulf has repeatedly evolved sea cow communities with different taxa over the past 20 million years and coincides with an Early Miocene marine biodiversity hotspot in Arabia, prior to its eastward shift to the Indo-Australian Archipelago where dugongs continue to thrive today.

Racicot et al. – Variation in whale (Cetacea) inner ear anatomy reveals the early evolution of “specialized” high-frequency hearing sensitivity.

As fully aquatic mammals, hearing is arguably the most important sensory component of cetaceans. Increasingly, researchers have been harnessing computed tomography (CT) to investigate the details of the inner ear as they can provide clues to the hearing abilities of whales. We use microCT scans of a broad sampling of the ear bones (periotics) of primarily toothed whales (Odontoceti) to investigate the inner ear bony labyrinth shape and reconstruct hearing sensitivities among these cetaceans, including several taxa about which little is currently known. We find support for sensitivity to the lower frequency spectrum in the archaeocete Zygorhiza kochii and an early toothed mysticete cf. Aetiocetus. Oligocene odontocetes (including one from our novel dataset), stem delphinidans, and two additional species of the long-snouted eurhinodelphinids are found to have been able to hear within the narrow-band high-frequency spectrum (NBHF), which is thought to be a specialized form of hearing that evolved convergently multiple different times in extant groups to avoid predation by macroraptorial predators. Our results thus indicate that NBHF evolved as early as the Oligocene and certainly in stem delphinidans by the early Miocene, and thus may be an ancestral characteristic rather than a more recent innovation in select groups.

Silaev et al. – Pleistocene Walrus on the Pechora River: Mineralogical and Geochemical Data and Paleoecological Reconstructions.

Fragments of the left tusk were studied in a Pleistocene walrus whose fossil remains were found on the bank of the Pechora River in 2009. The analyses covered granulometric, chemical, and normative-mineral composition of grounds surrounding the bones; thermal properties and chemical and trace element compositions of the tusk; X-ray diffraction parameters and chemical composition of bone bioapatite; macrostructure and elemental and amino acid compositions of bone organic matter; carbon and oxygen isotopic compositions of bioapatite; and carbon and nitrogen isotope compositions of bone collagen. Bioapatite showed moderately isotopically light carbon, which is characteristic of extracave fossil bones of Pleistocene animals, and isotopically heavy oxygen, which is typical of seawater bicarbonate. The isotopic data obtained for the organic matter of the Pechora walrus correlated with similar characteristics of marine animals, but suggest a fish diet rather than a mollusk diet, which is typical of modern walruses. The finding indicates that the habitat and diet of the Pechora walrus were unusual for marine predators.

Solis-Anorve and Buono – Cetotheriidae records from the Late Miocene of Patagonia expand the diversity of baleen whales from the Southwestern Atlantic Ocean.

The marine outcrops of the Patagonian Miocene (Argentina) encompass one of the most important assemblages of fossil mysticetes recorded worldwide, including key records of extant lineages. The Patagonian Late Miocene records comprise balaenids (right whales) or cetotheriids neobalaenines (pygmy right whales). In the last years, the increase of fieldwork efforts in Miocene outcrops of Patagonia has led to the discovery of new specimens, thus expanding our knowledge of mysticetes diversity from regional and global perspectives. In this work, we describe isolated ear bones collected from the Late Miocene Puerto Madryn Formation 12–2.7 Ma (Serravalian to Piacenzian), Península Valdés (Chubut Province), preliminarily attributed to Cetotheriidae. Although the lack of diagnostic elements precludes a more precise identification (at genus or specific level) within this family, our studies reveal a previously unknown diversity of morphotypes, indicating significant taxonomic diversity among these Patagonian mysticetes. In addition, the South Atlantic cetotheriid assemblage appears to be represented exclusively by large taxa, probably of pelagic habits, which may have facilitated their dispersal into the southern basins. Finally, these records suggest a rapid dispersion of cetotheriids from the Paratethys into the Southern Hemisphere during the Late Miocene, with the Southwest Atlantic Ocean representing their southernmost limit of distribution.

Strauch et al. – How is the third jaw joint in whales different? Diverse modes of articulation between the jaws of whales.

Cetaceans are a lineage of marine mammals that evolved diverse modes of aquatic feeding facilitated by modifications to the ancestral mammalian feeding apparatus, including the mandibular symphysis. In mammals, the mandibular symphysis is the third joint of the lower jaw. Articulation of the joint varies across mammalian clades, ranging from fibrocartilaginous connection to complete ossification. Whales span this range, with one lineage (baleen whales) evolving an unfused, highly mobile symphysis. This study conducts a comprehensive morphological investigation of the mandibular symphysis in whales. Here, we describe diverse joint morphologies based on observations of 152 cetacean mandibles representing 74 extant and fossil taxa. We also examine the internal architecture of the joint using computed tomography (CT) cross-sectional data. Based on gross anatomical observations of the osteology of the joint, we define four broad categories of symphyses: unfused, partially fused, fully fused, and decoupled. In odontocetes, articulation ranges from unfused mandibles to full fusion of the symphysis. The decoupled, highly mobile symphysis in crown mysticetes represents a novel condition unobserved in other mammalian clades. Partial fusion of the symphysis is the most common mode of articulation among the observed extant taxa, closely followed by unfused symphyses. In extant and extinct longirostrine taxa, full fusion coincides with an elongated symphysis. However, extant sperm whales (Physeter macrocephalus) notably exhibit an elongated, unfused symphysis that likely does not play a significant role in feeding. Observations of eminences on the posterior border of the symphysis in sperm whales and other suction feeders suggest that aspects of hyolingual musculature and function may be reflected in the morphology of symphysis. We suggest that further investigation of the symphyseal joint in marine mammals and other aquatic tetrapods will advance efforts to identify phylogenetic and ecological influences on the form and function of the feeding apparatus in an aquatic environment.

Strauch et al.– Morphological diversity of the cetacean mandibular symphysis coincides with novel modes of aquatic feeding.

In whales, extreme modifications to the ancestral mammalian feeding apparatus facilitate novel modes of aquatic feeding. These modifications manifest in morphological diversity across a suite of characters, including the mandibular symphysis. Cetaceans span a range of symphyseal morphologies, with one lineage (crown mysticetes) evolving a highly mobile condition unique among mammals. Here, we use phylogenetic comparative methods to examine the evolution of symphyseal fusion and elongation across 206 extant and fossil cetacean taxa. Ancestral state reconstructions corroborate observations from the fossil record that suggest the ancestral condition for Cetacea was a fused, moderately elongated symphysis. Shifts in symphyseal morphology coincided with ocean restructuring and diversification of feeding modes. Evolutionary rates peaked in the middle–late Eocene and at the Eocene/Oligocene boundary as whales evolved shorter, unfused symphyses. During the Eocene, ankylosed mandibles became less common with the appearance of increasingly pelagic whales. Mysticetes evolved decoupled, highly mobile mandibles near the Eocene/Oligocene boundary. Several odontocete lineages underwent a trait reversal and converged on fully fused, elongated mandibles in the Miocene. Analyses evaluating the influence of ecological variables indicate strong correlations in feeding strategy, dentition, and prey type. The loss of prey-processing behavior and changes to masticatory loading regimes may explain concurrent trends in symphyseal morphology and tooth simplification. We suggest that the functional and morphological diversity of the symphysis in whales is a consequence of aquatic feeding imposing different mechanical constraints than those associated with feeding on land.

Tanaka et al. – A new member of a large and archaic balaenid from the Late Miocene of Sapporo, Hokkaido, Japan partly fills a gap of right whale evolution.*

The family Balaenidae (right whales) includes two genera and four extant species, all of which are endangered and giant animals measuring approximately 17 to 20 m in length. The history of the Balaenidae spans about 20 million years. Several small sized extinct balaenids from the Pliocene have been identified. However, half of this history remains unknown owing to a 9-million-year gap from 15.2 to 6.1 m.y.a. in the fossil record. A well-preserved fossil balaenid skeleton, designated SMAC 2731, from the Late Miocene approximately 9 m.y.a. in Sapporo, Hokkaido, Japan, is named as Megabalaena sapporoensis gen. et sp. nov. This specimen preserves the skull, periotics in situ, tympanic bullae, right mandible, basihyal-thyrohyal, right stylohyal, sternum, seven cervical vertebrae, nine thoracic vertebrae, and 16 more posterior vertebrae, rib fragments, scapulae, and left forelimb elements. All preserved vertebral epiphyses are fused, indicating that SMAC 2731 was physically mature. Notably, M. sapporoensis can be distinguished from other balaenids by its excavated orbit in dorsal view with a large postorbital process, dorsoventrally high anterior part of the involucrum of the tympanic bulla, long compound posterior process, high coronoid process and deeper subcondylar furrow of the mandible, incipient cervical fusion (C2+C3 only), and its slender forelimb bones, including the humerus, radius and ulna. Based on a bizygomatic width of 2.2 m, the estimated total length of the holotype of M. sapporoensis is 12.7 m. Overall, M. sapporoensis indicates that balaenids diversified prior to the Late Miocene.

Tanaka – Whale fossils from the lower Miocene, Yoshino Formation, Katsuta Group, Okayama, Japan.

Five fossil whale bones discovered by Mr. Shingo Kishimoto from the Yoshino Formation, Early Miocene are identified as below. MNHAH D1-059542 is a left tympanic bulla (cf. Isanacetus laticephalus). MNHAH D1-059543 is a fragmentary cranium (Chaeomysticeti indet.). MNHAH D1- 059544 to 059546 are three vertebrae belonging to one individual (Cetacea indet.). These additional specimens supplement knowledge of Early to Middle Miocene whales in the region, and to compare with other areas for the future studies.

Tanaka and Taruno – Two new materials of whale remains from the Holocene (Quaternary) of Osaka, Japan: filling the age of lacking reports on Holocene baleen whales from Japan.

The book “Animal History of Japan” published in 1944 emphasized that “marine mammal study, especially on remains, has not yet begun.” At that time, there were not enough baleen whale remains. More remains were discovered from the 1960s. Since 2017, we have worked on baleen whale fauna reconstruction in the Holocene and Pleistocene of Osaka, Japan. We hereby summarize the reported Holocene baleen whales from Japan and report the finding of two additional baleen whale remains. In total, 13 Holocene baleen whale remains with morphological descriptions have been reported from Japan, with half of them being from Osaka. Comparison between the modern stranding records and baleen whale remains from Osaka indicates that the abundance of Balaenoptera physalus is a common phenomenon. However, the remains of Eubalaena sp. represents the differences between the past and the modern records, suggesting that the population of the right whale was larger during pre-historic times.

Terranova et al. – Retrieving Palaeoecological Information from Historic Fossil Finds: A Taphonomic Cold Case from Orciano Pisano (Central Italy) Reveals a Distinctive Trophic Interaction in the Pliocene Mediterranean Sea.

Evidence of trophic interactions between sharks and cetaceans is rather widespread in the fossil record, consisting as it does of tooth marks on bones and rarer teeth or tooth fragments embedded in (or associated with) skeletal remains. Here, we reappraise a partial mysticete (baleen whale) forelimb that was collected more than a century ago from Pliocene deposits exposed at the celebrated fossil locality of Orciano Pisano (Tuscany, central Italy). This specimen, which is revealed to originate from an early juvenile individual, features shark tooth marks on both the humerus and radius. Whether these traces are due to active predation or to scavenging cannot be ascertained. During the Pliocene, the Mediterranean Basin was inhabited by a diverse elasmobranch fauna, including a number of mammal-eating forms that no longer inhabit the Mediterranean Sea (e.g., Galeocerdo and some Carcharhinus spp. as well as the extinct Parotodus). Early juvenile mysticetes were also likely more common than today in the Pliocene Mediterranean Sea, which may have contained balaenid and balaenopterid calving grounds, thus providing the Mediterranean mammal-eating sharks with vulnerable, energetically valuable potential prey items. Thus, our results evoke a kind of trophic interaction that was likely common and ecologically relevant in the Pliocene Mediterranean Sea.

Valenzuela-Toro et al. – Aquatic sloths (Thalassocnus) from the Miocene of Chile and the evolution of marine mammal herbivory in the Pacific Ocean.

The evolution of marine mammals in South America includes unique and extinct lineages found nowhere else in the world, such as the walrus-convergent whale Odobenocetops and multiple aquatic sloth species belonging to the genus Thalassocnus. Aquatic sloths have been collected from Mio-Pliocene marine deposits in Peru and Chile, and terrestrial deposits in Argentina. In Chile, these occurrences range over 800 km across several basins from the Bahía Inglesa, Coquimbo, and Horcón formations. Here we report aquatic sloth material belonging to the species Thalassocnus natans from a new locality, Norte Bahía Caldera from the Bahía Inglesa Formation in the Atacama Region. We find multiple lines of evidence to support a late Miocene age for this material, which consists of a nearly complete skeleton, including cranial and postcranial remains and associated mandible and postcranial elements that represent the most complete Thalassocnus specimens reported yet from Chile. Based on this finding, we review the stratigraphic origin and geologic age of Thalassocnus species from the western coast of South America and determine that remains from the Upper Pliocene of central Chile represent the youngest known record of this genus to date. Our review also suggests that overlapping stratigraphic ranges for type material of T. antiquus with both T. natans and T. littoralis weakens the proposed argument for Thalassocnus evolution through anagenesis succession. Finally, in the context of Thalassocnus material from Chile and Peru, including other marine mammal herbivores (e.g., sirenians), we demonstrate that one of the most unusual features of this guild is that South American marine mammal herbivores did not reach the body sizes of their analogous counterparts (i.e., desmostylians and sirenians) in the North Pacific. This observation builds on other paleontological evidence about the unusual features of the Peruvian biotic province during the Neogene.

Valenzuela-Toro et al. – Historical and ongoing inequities shape research visibility in Latin American aquatic mammal paleontology.

Latin American aquatic mammal fossils offer key insights into the evolution of life in the Southern Hemisphere. However, many fossils are housed in Global North institutions and are studied by overseas researchers. Latin American women researchers also face gender bias that undermines their ability to study fossils, publish, and gain peer recognition. We conducted a bibliographic analysis of studies on fossil aquatic mammals published between 1990 and 2022 to investigate the impacts of scientific colonialism and biases on research and citation patterns in Latin American paleontology. We show that Global North-based researchers published more on Latin American fossils than their Latin American counterparts. Multinational teams authored nearly half of the publications, which are still heavily skewed toward Global North authors. Women led 24% of the articles and were underrepresented in most studies. Papers with more authors received more citations; however, papers with a higher proportion of Latin American authors and published in languages other than English received lower citation rates. The journals’ impact factor affected citation rates for articles authored by Latin American and women, but not by Global North researchers or men. Our paleontology case study shows widespread invisibility for Latin American researchers.

Van Vliet et al. - Pachycetines from the Hampshire Basin, England and the distribution of pachycetines in Europe, with a note on Pachycetus humilis Van Beneden, 1883.

Archaeocete remains are occasionally found in the Bartonian part of the Barton Clay Formation of Barton-on-Sea, Hampshire, England and have been described in the 19th and 20th century. Two taxa were recognised, a rather large one, ascribed to Basilosaurus sp. and a smaller one, ascribed to ‘Zygorhiza’ wanklyni Seeley, 1876. First focus in this article is on remains from Barton-on-Sea, England, apparently belonging to pachycetine basilosaurids. Two species of Pachycetus, also here a large and a small one are distinguished. The large taxon, represented by a vertebra, is assigned to Pachycetus cf. paulsonii (Brandt, 1873). The small taxon could be identified after re-evaluation of three vertebrae of the small Pachycetus humilis Van Beneden, 1883 from the Bartonian-Priabonian of the Helmstedt region, Germany. Only one, a thoracic vertebra, NsT91 appears to belong to a small pachycetine basilosaurid and is here designated as lectotype of the species. It has several features with which it can be distinguished from torso vertebrae of P. paulsonii. Vertebrae of the small pachycetine taxon from Barton-on-Sea with similar features are assigned to Pachycetus cf. humilis. No remains of Basilosaurus are recognised, but with both a large and a small pachycetine taxon plus a small dorudontine basilosaurid, ‘Zygorhiza’ wanklyni, three archaeocete taxa are now known from the Bartonian of Barton-on-Sea, England. Second focus in this article is the distribution of Pachycetus cf. paulsonii and Pachycetus cf. humilis in Europe, which show clear connections of the Bartonian Hampshire Basin with the North Sea Basin.

Veress et al. – Overview of the Transylvanian Paleogene sea cows’ distribution records, with a focus on a new Oligocene locality.

In the past, a fairly large number of Paleogene sirenian fossils were collected in the Transylvanian sedimentary basin, and although the study of these marine mammals has apparently decreased considerably in recent years, the data already resulting from these discoveries are important and deserve discussion. Such data refer to localities where these fossils were unearthed. Analyzing the papers belonging to various contributors, both old and recent, and performing our field studies, we made a list of these localities in Romania, where sirenian fossils have been unearthed. Except for a single find recorded outside the Carpathians, all others are directly related to the Transylvanian Basin, in various Paleogene marine formations. This work is related to these sites and highlights a few cases where such fossil sites can no longer be accessed, either due to natural or human influences. These fossils are useful markers of marine and even brackish shallow seas, allowing for paleogeographic reconstructions. We also report a new locality with Oligocene (Rupelian) sirenians in the Transylvanian Basin, at Bizușa-Băi (Sălaj County). It is further evidence of the continuity of the group of marine mammals even after the "Grande Coupure", in Romania.

Viglino andPark – River dolphin cochlea has not evolved convergently.

Convergence is often invoked to explain some common morphological features in the crania and postcrania of river dolphins (Cetacea, Odontoceti). Rivers are a challenging, complex and increasingly threatened habitat, and echolocation is a critical tool for their survival. Cochlear morphology can be indicative of hearing and echolocation abilities in toothed whales. Previous analyses of river dolphin cochleae have not included all extant riverine taxa, potentially obscuring their patterns of evolution. Based on three-dimensional models obtained from micro-CT scans and using a more inclusive definition of river dolphins, we tested for convergent evolution in cochlear morphology, including extant and extinct species in a broader evolutionary framework. Results showed that the cochlea of river dolphins is not significantly disparate from marine forms, and there is more interspecific morphological variability than expected. Statistical analyses also revealed the lack of convergence in the cochlea and that other ecological variables shaped the intricate evolutionary landscape of this structure. We hypothesize that river dolphins solved the challenges imposed by the environment via their sound production apparatus (e.g. skull shape, melon, etc.) rather than the cochlea.

Watmore et al. – Gigantic Macroraptorial Sperm Whale Tooth From the Miocene of Orange County, California.

Sperm whales are represented by three widely distributed species, Physeter macrocephalus, the giant sperm whale, Kogia breviceps, the pygmy sperm whale, and K. sima, the dwarf sperm whale. The group has an extensive fossil record, with at least 20 genera going back to the Late Oligocene (recently reviewed by Boersma and Pyenson 2015). Additional questionable genera are represented by isolated fragmentary specimens, including teeth. According to Velez-Juarbe et al. (2015), the modern Physeteridae are a relatively derived branch of the group they called the Pan-Physeteroidea. More basal members of the clade are varied, with different features and sizes. One of the largest was the giant macroraptorial whale Livyatan melvillei (Lambert et al. 2010), which may have reached 13–17 m in total body length. It had large piercing teeth in both the upper and lower jaws, up to 362 mm long, making them the largest non-tusk teeth known in any mammal. The teeth equipped the animal for catching large prey such as other whales and sharks, as well as smaller animals (Bianucci et al. 2015). In contrast, the modern sperm whale,
P. macrocephalus, has relatively small upper teeth that do not erupt until around sexual maturity, while the lower jaws consist of larger, conical teeth (Berkhovitz and Shellis 2018). Both Physeter and Kogia are known suction-feeders, generating negative pressure at their gape to capture soft-bodied prey like deep-sea-dwelling giant squids. As discussed below, teeth of Livyatan and/or possibly referable to Livyatan have been reported from Peru, Argentina, Chile, and South Africa (Lambert et al. 2010; Piazza et al. 2018; Gutstein et al. 2015; Govender 2019). Here we describe the first specimen reported from North America and the North Pacific realm.

Remarks: I actually held and personally examined this specimen at the Cooper Center earlier this year! It is large, but it did not strike me as being gigantic. However, the comparison image and the measurements don't lie: it is almost as enormous as Livyatan. I take it back, and I suppose I have overestimated the size of the teeth of the holotype specimen of Livyatan in the past. This would actually indicate that there are probably quite a lot of Livyatan teeth sitting in museum and private collections up and down the east coast of the US.

Wilhite – Mammalia: Cetacea. (In Vertebrate Fossils of Louisiana).

The order Cetacea currently consists of approximately 86 species, 46 genera, and 14 families. They have a worldwide distribution and include the heaviest animals known. Few fossils of the extant order Cetacea are known from Louisiana. Rather, virtually all known Louisiana fossil whales belong to the paraphyletic group known as archaeocetes (ancient whales). With one possible exception, all Louisiana whale fossils are Eocene in age. Currently three genera of fossil cetaceans are recognized from Louisiana including Basilosaurus, Zygorhiza, and Natchitochia. A fourth named archaeocete genus, Pontogeneus, is now considered by many workers to be nomen nudum (Uhen 2005). Significantly, the type specimens of both Basilosaurus and Natchitochia are from Louisiana. The most complete archaeocete fossil from Louisiana is LSUMG-V-1, a Basilosaurus specimen consisting of a well-preserved skull, thoracic limb, and anterior thorax. While Zygorhiza is a very well represented genus in both neighboring Mississippi and Alabama, the few isolated specimens identified from Louisiana cannot in most cases be linked to even a specific formation as they were all found as isolated elements weathered from their parent outcrop. The majority of the information that follows will focus on LSUMG-V-1 which is figured extensively for the first time here.

Remarks: Archaeocete whales have received their fair share of attention - and though I have lamented in the past that 'archaeocetes have been done to death', I mostly have studies of their postcrania in mind. Their skulls have nearly been ignored by archaeocete researchers focusing on the macroevolutionary land to sea transition. As such, with any new specimen reported, it's an opportunity to learn quite a bit more about their skull anatomy. This spectacular specimen has been known about for decades, but was included within a thesis that was never published and therefore, it was 'off limits' for decades. Though the chapter is short, it does include some nice photographs and surface scans of the Louisiana State specimen of Basilosaurus cetoides. I look forward to more formal descriptions of this skeleton, which also includes vertebrae and well-preserved forelimbs.

The fossil record of early cetaceans from New Zealand, 2: baleen-bearing whales from the Oligocene and early Miocene

2025-12-15T03:00:00.000-08:00

For an introduction to the geology, stratigraphy, archaeocetes, and toothed mysticetes of mid-Cenozoic Zealandia, see part 1 here.

For part 3, on the fossil toothed whales - Odontoceti - from New Zealand, click here (coming next Monday!)

Life restoration of a New Zealand eomysticetid by the kiwi artist Chris Gaskin: this was originally supposed to be the Earthquakes eomysticetid, now Waharoa, but we used it instead for the "Island cliff" eomysticetid Tokarahia. Copyright Chris Gaskin/Otago Geology Museum; from Boessenecker and Fordyce (2015c).

Two professors and accidental paleocetologists: Professor William Benham (left, 1860-1950), ca. 1907, and Professor Brian Marples (right, 1907-1997), ca. 1967. These two gentlemen were responsible for studying the bulk of early discoveries of fossil whales. Marples work tended to be more careful, though he had the benefit of working during a more scholarly connected era and a greater pool of knowledge. Benham named Mauicetus parki and Marples named "Mauicetus" lophocephalus (now Tokarahia lophocephalus). Ewan Fordyce met Marples on several occasions and loved the guy.

The discovery of Mauicetus parki - the first early mysticete from New Zealand

In 1937, Professor William B. Benham of the Department of Zoology at the University of Otago published a short paper naming the new cetacean Lophocephalus parki, based on a broken braincase from an unknown locality, but most likely the Milburn Limestone at the Milburn Lime Quarry just about 40 km southwest of Dunedin (and, for anyone flying in to the country, quite close to the airport). Professor Benham noted that the skull was clearly not from a "squalodont" - which, as you may have guessed from part 1, and will be expanded upon in part 2, most heterodont cetaceans from the Oligocene and early Miocene were identified as "squalodonts" - but did not initially consider it to be a baleen whale. Based on the sagittal crest and narrow occipital shield, he considered Lophocephalus (ridged head, after the tall muscle attachment crests) to be an archaeocete whale. Another specimen, which he thought was from Lophocephalus, included a partial mandible and some blocks of limestone with associated teeth - Benham assumed these were from the same species, writing "I think I am justified in associating these teeth with those from Waimate, and attributing them to Lophocephalus parki."

The unassuming fragmentary braincase of Lophocephalus parki, from Benham (1937).

Benham's (1937) initial interpretation of Lophocephalus parki as an enormous archaeocete. Correspondence with Remington Kellogg would pointed out that the frontoparietal suture is present in the fragment, meaning that the skull is considerably more telescoped than Benham thought, and that it represented a mysticete.

Some of the specimens that Benham (1937) initially referred to Lophocephalus parki - a completely reasonable action given that he thought it was an archaeocete. Later it would become obvious that these were in fact odontocete specimens, now considered Squalodon or something similar.

This conclusion, however, was fleeting. Benham wrote a followup paper five years later in 1942 that precipitated from letters he had received from Remington Kellogg of the Smithsonian Institution in 1940. Kellogg pointed out that the braincase was much more complete than had been assumed by Benham, who had missed the frontal-parietal suture, though clearly present in his published photographs. Kellogg wrote that the skull was rather similar to Aglaocetus moreni, redescribed and illustrated by Kellogg in 1934. Further, Benham (1942) wrote that "after distribution of reprints of that article, my attention was drawn by a zoologist in America to the devastating fact - which I confess I had overlooked - that this generic name [meaning the genus name Lophocephalus] had been bestowed already on three animals of widely different groups, viz., on a Gregnarine, on a beetle, and on a fish! Hence, it is necessary to substitute another name for this extinct whale." Benham recognized that the specimen was in fact a baleen whale, and named it Mauicetus parki. Benham (1942) was forced to essentially re-publish a basic description of the fossil owing to the fact that, at the time, it was typical for descriptions to essentially consist of a long list of comparisons, his mistaken identity in 1937 sadly resulting in some anatomical misinterpretations that made the original study practically useless in most regards. In the 1942 redescription, Benham makes extensive comparisons with Aglaocetus moreni, and concludes that, thanks to Kellogg's correspondence, Mauicetus parki is indeed a "cetothere".

Cheng-Hsiu Tsai examining the postcranial bones of ZMT 67, a very large Mauicetus-like mysticete from the very top of the Otekaike Limestone, dating to the lowermost Miocene (Aquitanian). The specimen is still undescribed and was the focus of Hiroto Ichishima's doctoral thesis at Otago.

How do you photograph a whale skull? Lots of lighting, and by using the stairwell outside Ewan's office! Ewan had a homemade wooden clamp to clamp is camera onto the wooden railing, and depending upon the size of the whale, we would use either the lower or the upper railing nearer the first floor (=second floor in America). Here Felix and Ewan have an elaborate lighting setup, including the use of foam to bounce light to maintain correct lighting from the upper left (I presume the skull was intended to be oriented with its nose pointing to the left side of the figure). This is the referred juvenile skull of Mauicetus parki.

Ewan Fordyce and colleagues would go on to find many more Mauicetus-like fossils, including some fragmentary specimens reported by Hiroto Ichishima in his (unpublished) doctoral thesis. One specimen, collected not by Ewan but by F.M. Climo and colleagues in 1971, ZMT 67, is a large, 2.5 meter long partial skull with some postcrania that represents either a species of Mauicetus or a closely related genus. This specimen is earliest Miocene in age and from the very top of the Otekaike Limestone. In 2004 or so, Ewan and field assistants excavated a partial skull of a juvenile Mauicetus parki from Haugh's Quarry in the Hakataramea Valley of South Canterbury. He presented this in his 2005 presentation at the Society of Vertebrate Paleontology meeting in Mesa (Phoenix) Arizona, my first SVP - ten of us undergraduate students from Montana State University had carpooled down from Bozeman on a group road trip, taking turns napping and driving, in a 14 hour trek. I had been interested in fossil marine mammals, and just finished my first field season of permitted field work - and eagerly attended the marine mammal session on the morning of the second day. I saw a talk by Phil Gingerich on the giant archaeocete Basilosaurus isis from Egypt, a talk by Larry Barnes on kentriodontid dolphins from Calvert Cliffs, a talk from Mark Uhen on xenorophid dolphins from Onslow Beach, North Carolina (published three years later as Albertocetus), and a talk by Ewan Fordyce on a mysticete skull from New Zealand. I was shocked as Ewan described how he would excavate these specimens from the soft, sandy limestone with a chain saw. The entire excavation - which would have taken a crew of 3-4 pick/chisel-armed graduate students 3-4 days to excavate - took Ewan only about 2-3 hours! This material is still not yet published, unfortunately, but my doctoral labmate Felix Marx is continuing Ewan's research on Mauicetus. All I can say about Mauicetus parki is that it has an acutely triangular occipital shield, and earbones and mandibles that are similar to but slightly more primitive-looking than those in American "cetotheres" like Diorocetus and Parietobalaena. One of the key features I can mention is that Mauicetus has one critical earbone feature that is shared with modern baleen whales, to the exclusion of toothed mysticetes and eomysticetids: the posterior process of the two earbones (periotic and bulla) are fused into a long, cylindrical process. Near the base of this structure, the elliptical foramen in the bulla is also closed up. Mauicetus is the oldest known mysticete with these features.

The holotype skull of "Mauicetus" lophocephalus, from Marples (1956): on the right, the skull is shown as it was discovered and excavated in the Kokoamu Greensand. On the left is the skull as it was prepared, prior to being lost sometime in the 1960s or 1970s. At first glance, the skull of Mauicetus parki looks rather similar...

The holotype tympanic bulla of "Mauicetus" lophocephalus, from Marples (1956). Very obviously an archaic mysticete given how similar it is to basilosaurid whales.

The holotype atlas and axis vertebrae of "Mauicetus" lophocephalus (left) and "Mauicetus" waitakiensis (right), from Marples (1956).

More Mauicetus, of Marples: Mauicetus lophocephalus, Mauicetus waitakiensis, and Mauicetus brevicollis

Professor Brian J. Marples of the University of Otago Zoology Department was an accidental paleontologist. He was actually an arachnologist - specializing in the zoology of trap-door spiders in New Zealand. In the 1940s, his work on these spiders brought his nose to the ground in the vicinity of the Waitaki River - and Oligocene rock layers. As a result, he and his students discovered some interesting cetacean and penguin fossils. He published on some of the fossil penguins in 1952, identifying them as Palaeeudyptes antarcticus. These identifications were determined later to be too conservative, and several were named as new species after Marples (by none other than G.G. Simposon) along with the new genus Marplesornis. Marples also found several baleen whale specimens consisting of partial skeletons, which he named in a 1956 paper, all from the Kokoamu Greensand (Duntroonian stage, 27-25 Ma). The most spectacular of these was named Mauicetus lophocephalus - amusingly re-using Benham's original genus name for Mauicetus - based on a partial skull with mandibles, periotic fragment, tympanic bullae, and some neck vertebra. A somewhat more fragmentary specimen consisting of the occipital bone, tympanic bullae, and neck vertebrae was named Mauicetus waitakiensis, and a third specimen consisting of a string of vertebrae was named Mauicetus brevicollis. Mauicetus lophocephalus was unusual in having a relatively primitive looking skull, and three images were produced: a photograph of the specimen in situ as it was discovered, a photograph of the braincase, unfortunately missing most of the rostrum which was apparently destroyed during excavation. The third image is a line drawing, which Fordyce suspected Marples drew while in the field - giving us a near-accurate view of the outline of the complete skull. The skull has a triangular rostrum, very long nasals and a bony naris (blowhole) set far out on the rostrum, large temporal fossae with medially bowed zygomatic arches, and a narrow intertemporal region of the skull with a small, narrow, posteriorly positioned occipital shield and vertex. Another skull resembling this would not be discovered again in New Zealand - or elsewhere on earth - until the 1980s.

The holotype skeleton of Horopeta umarere, from Tsai and Fordyce (2015): fossil locality, the excavation of it and a manmade cave in the Otekaike Limestone, and the specimen before and after final preparation by Tsai. I believe Craig Jones is the man in the hole.

The unusually robust sternum of Horopeta umarere. It retains an archaic rod-like structure with expansions at either end, and articular facets for multiple pairs of ribs; eomysticetids, on the other hand, had plate-like, triangular sterna with no obvious deep facets like this, implying only a single lightly attached pair of ribs as seen in the rest of Crown Mysticeti. From Tsai and Fordyce (2015).

Horopeta umarere - the oldest known gulp-feeding mysticete

A large mysticete was excavated from a cliff on the southeast side of Haugh's Quarry in 1988 by Ewan and his preparators Andrew Grebneff and Craig Jones. This specimen has a partial braincase, very well-preserved earbones, partially preserved mandibles, a sternum, and an articulated vertebral column with some ribs. This specimen served as the core specimen in my labmate Cheng-Hsiu Tsai's doctoral thesis, sort of a 'sequel' to Ichishima's 1997 thesis, and was published by Tsai and Fordyce in 2015. They named it Horopeta umarere roughly - translating from Maori to gulper with an unusual sternum . The specimen is from the base of the Duntroonian in the Kokoamu Greensand, dating to around 27-26 Ma. The skull is similar to Mauicetus, as are the earbones - yet they exhibit some features more reminiscent of eomysticetids: there is an open elliptical foramen in the bulla, and the posterior processes are not yet fused. However, the real revelation comes from the mandibles - they are robust, with a D-shaped cross-section, have a large and laterally curving coronoid process and are laterally very strongly bowed - much more strongly bowed than in eomysticetids, and resembling some Miocene "cetotheres" sensu lato ("kelloggitheres") as well as modern balaenopterid whales. This enormous mouth indicates that Horopeta was strongly adapted towards 'gulp feeding' - a more descriptively neutral term for a whale that takes in great mouthfuls of water to filter feed, like the lunge feeding behavior of modern balaenopterids. The sternum is quite robust and rod-like, with attachment points for three ribs - quite different from the plate-like sternum with an attachment for a single pair of ribs in modern mysticetes. Mysticetes tend to only have a single sternal bone - the manubrium, the anteriormost sternal bone, and all of the others, including the posteriormost one, the xiphisternum, are lost. Like other early mysticetes, there doesn't appear to ben articulation for a second sternal body. The robustness of the sternum in Horopeta is quite similar to toothed mysticetes like Llanocetus, Aetiocetus, and Mammalodon, and generally quite different from eomysticetids and modern mysticetes, suggesting a reversal or parallel evolution of a plate-like sternum.

Some of the postcranial bones and mandible segments of Horopeta umarere (OU 21982) spread out in the lab after removal from the main jacket.

Cheng-Hsiu Tsai examining the postcranial bones of Horopeta umarere on the big wooden table in the Otago Geology museum. This famous wooden table has been there for over a century and serves as a place to lay out big specimens, a space for photography, dissections of smallish cetaceans, and tea time in winter when it's too chilly to take afternoon tea on the steps outside (or, raining). Photo taken by me.

The holotype earbones of Horopeta umarere: it really, really looks like Mauicetus parki, and in many regards, the earbones are a mishmash of archaic features you might expect in an eomysticetid and derived features you would see in a middle Miocene "kelloggithere" like Parietobalaena. From Tsai and Fordyce (2015).

The holotype braincase fragment of Whakakai waipata: a very flat skull, but still poorly telescoped, somewhat more derived than eomysticetids. From Tsai and Fordyce (2016).

The deeply unusual earbones of Whakakai waipata: the periotic is just massive, generally looking like a hyperinflated eomysticetid periotic. The bulla is nearly indistinguishable from Horopeta and Mauicetus. From Tsai and Fordyce (2016).

Tsai's whales - Whakakai waipati and Toipahautea waitaki

These whales have no common name, and since both were from chapters of Cheng-Hsiu Tsai's thesis, I've always just called them "Tsai's whales". These are two very unusual species, mostly diagnosed from their earbones. They are similar to an unpublished gigantic mysticete from the Kokoamu Greensand that is not yet named, but called the "chocolate whale" - generally resembling a gigantic eomysticetid, though with quite different-looking earbones. We don't yet have a complete skull of one of these things, but I expect study of the "chocolate whale" to reveal an eomysticetid-like morphology. The earbones include a tympanic bulla that is somewhat more like Mauicetus and Horopeta, but unusual periotics that are massively inflated with unfused posterior processes, quite unlike anything else known from the early fossil record of mysticetes. Whahakai waipata (pronounced "fah-caw-kye"; "Wh" in the southern Maori dialect is an "f" sound, see the pronunciation guide in part 1) was named by Tsai and Fordyce (2016) and has a partial braincase, and the top of the skull is a bit flat relative to eomysticetids, and seems to lack a clear sagittal crest - and has an intertemporal constriction that is somewhat shorter than eomysticetids. The periotic, in many regards, looks like an eomysticetid periotic that has been inflated like a balloon - and it's not inconceivable that, with the description and coding of more specimens, these might form a clade with eomysticetids based on some of the earbone features.

The "chocolate whale" on display at the Otago Museum: perhaps the largest fossil cetacean skeleton that Ewan excavated from New Zealand. The skull block of Tokarahia was larger than the individual blocks here, but Tokarahia is a smaller whale; this thing is like four meters across from the lumbars to the rostrum. This was originally intended to be part of Tsai's thesis, but did not make it in there. This whale is something similar to Whakakai, and also bears some similarities to eomysticetids. Some aspects of the skull also remind me of Llanocetus, though it is certifiably a toothless mysticete. Photo taken by me.

The skull of the "chocolate whale", here looking a little less chocolate-y owing to overexposure from my flash. This skull is nearly a meter wide. Photo by me.

The excavation site and preparation of Toipahautea waitaki: in the upper left you can see Ewan posing with the weathered remains of the excavation pit, during the same field trip I posted photos of in part 1. The excavation hole for the "chocolate whale" is about 20 feet to the right, and the pit for Horopeta is about 100 feet to the left (just beyond the quarry equipment in the bottom photo).

The holotype skull and earbones of Toipahautea waitaki - at an early stage this was thought to perhaps be another Oligocene balaenoid, owing to the very steep occipital shield, which, admittedly, is vertical. However, phylogenetic analysis did not bear this out, and Toipahautea ended up being recovered as a Mauicetus/Horopeta-grade whale. From Tsai and Fordyce (2018).

Phylogenetic analyses of these whales from Tsai and Fordyce (2018). All analyses I'm aware of, including those conducted using my matrix and Felix Marx's matrix, show these whales as occurring between eomysticetids and Crown Mysticeti - indicating that these are likely to be the whales that crown mysticetes evolved directly from.

Two years later, Tsai and Fordyce (2018) named Toipahautea waitaki based on a slightly more complete specimen that preserves much of the base of the rostrum, parts of the braincase, periotic, bulla, mandible fragments, neck vertebrae, and scapula. Like eomysticetids, the nasal bones are long, the supraorbital process of the frontal is long and bears a large orbit, and the rostrum itself is quite wide - though we don't know how long. The braincase is poorly preserved, but the occipital shield seems to be vertical - resembling right whales - though the shield likely curved anteriorly. Like eomysticetids, the joint for the mandible is very large and shallow. The periotic is somewhat similar to Whakakai, but also shares some similarities with Horopeta.

Comparison of fossil cetaceans: Zygorhiza (A), Agorophius pygmaeus (B), "Mauicetus" lophocephalus (C) and Aglaocetus moreni (D). From Marples (1956).

Mauicetus or mistaken identity? New Zealand Eomysticetidae

In the 1980s and 1990s Ewan Fordyce excavated a number of skulls he recognized were similar to Mauicetus lophocephalus, but was not quite close to naming yet. Sadly, fossils from the Oligocene Chandler Bridge Formation of South Carolina, USA, were discovered and named Eomysticetus by Al Sanders and Larry Barnes in 2002. Ewan quickly realized that this collection of about a half dozen skulls from New Zealand represented eomysticetids, and likely several genera; this family was basically defined by the relatively primitive features outlined above: long nasal bones, long, non-telescoped intertemporal constriction, large temporal fossae, long zygomatic processes, and archaeocete-like earbones. In 2006 Ewan presented these specimens in an oral presentation at the Society of Vertebrate Paleontology meeting in Ottawa, Canada, during a symposium on the Origin of Neoceti - my second SVP meeting. I was wowed by the number of specimens, excellent preservation, and the diversity - they appeared to represent at least 3-4 species. The following year I dug up and prepared a specimen of the much younger baleen whale Herpetocetus from the Purisima Formation in Santa Cruz, California, and presented it at the 2008 SVP in Cleveland, Ohio - after which, Ewan approached me and asked if I was applying to doctoral programs yet. "Not yet! I'm only two months into my master's program!" I exclaimed. "Well, when the time comes, keep New Zealand in mind." I did, and three years later I was accepted into the doctoral program with a scholarship; Sarah and I flew down to Dunedin in March 2012, and I started my work on these specimens. At first there wasn't room to bring out all the skulls for side-by-side comparison, so Ewan encouraged me - in the rare chances we had to chat during my first few months, given that he had around 12 doctoral, master's, and P.G. Dip. Sci. students - to first look at all of the periotics and bullae. Each of the new skulls had at least one periotic and one bulla associated with it. My goal was not only to figure out 1) how many genera and species were present amongst the new specimens, but 2) which might be the same species, or same genus, as the species named by Marples (only Mauicetus lophocephalus and Mauicetus waitakiensis were considered to be eomysticetids; Mauicetus brevicollis is something much closer to Mauicetus parki); 3) determine whether any of these species belonged in the same genus or if they were 'monospecific', and 4) to determine whether any of these were assignable to an existing genus/species from elsewhere (e.g. Eomysticetus, Micromysticetus, Yamatocetus). After a couple of weeks acquainting myself with these specimens and poring over the earbone anatomy of basilosaurid whales and toothed mysticetes, I finally got some clarity and made some predictions about what skulls might be conspecific and which ones were not.

Excavation of Waharoa specimens: the "earthquakes" specimen (holotype), A; the springside cleft juvenile (OU 22075, shown in B in following image), B; and the Hakataramea quarry juvenile/paratype specimen (OU 22163, shown in C in the following image), C.

The full collection of fossil eomysticetids from New Zealand, collected by Ewan Fordyce and colleagues, along with the earbones of "Mauicetus" lophocephalus. From Boessenecker and Richards (2024).

Sadly, one development hampered my research somewhat. Sometime in the late 1950s, and prior to 1962, the Zoology Department moved buildings on Otago campus and the paleontology collections were transferred to the Otago Museum just across Cumberland street from campus. While the earbones, vertebrae, and mandible of Mauicetus lophocephalus were transferred and survive to this day, the skull - embedded in a large block of plaster - was lost, presumably discarded by university maintenance staff during the move. Ewan thought that the skull probably would have looked like a large rock on the floor, and staff may not have spoken to anyone in Zoology with direct knowledge of the specimen. Who knows what other rocks had been earmarked for the rubbish skip (=dumpster for my American readers); the skull is probably sitting in the landfill in Burnside, just south of town.

The full collection of eomysticetid earbones I had at my disposal during my Ph.D. Every single holotype specimen is in here, and each and every one of these specimens is now published.

The excavation of OU 22235, the "Island cliff" eomysticetid, aka "big scapula" mysticete, now the Tokarahia kauaeroa holotype - this hole was quite spectacular nearly 20 years later, and I'm pissed I didn't get a photograph of it. From Boessenecker and Fordyce (2015c).

Ewan posing for scale with our cast of the Tokarahia kauaeroa holotype slab (OU 22235).

The holotype skull block of Tokarahia kauaeroa as prepared. This block is huge and very difficult to move; because I couldn't get far enough away from the specimen to photograph it in one shot, I decided to photogrammetize the entire thing, and make a 3D model. This is actually the 3d model. From Boessenecker and Fordyce (2015c).

The evolution of the mysticete skeleton, skull, and tympanic bulla. From Boessenecker and Fordyce (2015c).

In the end, I came to the conclusion that there were six species present in four genera. Neither Mauicetus lophocephalus nor Mauicetus waitakiensis were assignable to Mauicetus, which likely belongs in a completely different (but as yet unnamed) family - and these species were instead identifiable as eomysticetids. The Island Cliff eomysticetid, OU 22235, was the largest single fossil that Ewan had ever excavated, and left in its 500 lb plaster jacket and prepared in relief. The tympanic bulla of this was quite similar to Mauicetus lophocephalus, and this specimen was named Tokarahia kauaeroa (Tokarahia, after Tokarahi - the Maori name for the mesa called "Island Cliff" by white settlers, and kauaroa meaning long jaw) in one of my thesis papers (Boessenecker and Fordyce, 2015c); we transferred Marples' species, with the new combination Tokarahia lophocephalus. One specimen of Tokarahia produced a putative tooth - these mysticetes were initially assumed to be toothless, and this discovery suggested that eomysticetids represented an intermediate stage between the toothed and baleen-bearing aetiocetid toothed mysticetes, and the completely toothless mysticetes of the Miocene and onward. Tokarahia, along with Waharoa (see below), suggest an intermediate stage with vestigial, functionless teeth along with baleen.

The holotype skull of Tohoraata raekohao in dorsal, ventral, and lateral view, along with a reconstruction of the skull, and the holotype braincase fragment (occiput) of Tohoraata waitakiensis (upper right). From Boessenecker and Fordyce (2015b).

The holotype periotic of Tohoraata raekohao and a diagram of the auditory region. From Boessenecker and Fordyce (2015b).

The holotype tympanic bulla of Tohoraata raekohao (left) and Tohoraata waitakiensis (right). From Boessenecker and Fordyce (2015b).

A much more partially preserved specimen consisting of a very big baby (well, juvenile) skull with distinctive earbones, known as the Harvey Farm whale, was named Tohoraata raekohao - tohoraata meaning 'dawn whale' and raekohao meaning 'forehead holes', referring to the distinctive foramina in the frontal bones. The short bullae with triangular outlines matched those of Mauicetus waitakiensis, so we recombined Marple's second eomysticetid as Tohoraata waitakiensis.

The Earthquakes eomysticetid - the holotype skull of Waharoa ruwhenua. From Boessenecker and Fordyce (2015a).

Juvenile eomysticetids - the juvenile paratype skull of Waharoa ruwhenua (left), the perinatal/young juvenile (referred skull, not a paraype) on the upper right, and the holotype perotic of Waharoa. From Boessenecker and Fordyce (2015a).

Were eomysticetids the last toothed mysticetes? Juveniles and adults of Waharoa have three suspicisously tooth socket-looking foramina in their premaxilla, which suspiciously also houses three teeth in most placental mammals (and all toothed mysticetes and archaeocetes). There are additionally similar structures in the tips of the mandibles. Are these alveoli? We cautiously interpreted them as possible alveoli. From Boessenecker and Fordyce (2015a).

Growth changes in Waharoa ruwhenua. On the left are histological samples taken from the ribs of the young juvenile (OU 22075), older juvenile (OU 22163), and the adult holotype (OU 22044); woven bone is present in the juveniles, confirming juvenile status, and there is highly remodeled haversian bone present in the holotype, confirming adult status. This is not as accurate as counting LAGS (lines of arrested growth), but is useful as a general rule of thumb: baby, subadult, or mature adult - in a relative framework. On the right, the earbones of Waharoa change: the tympanic bulla actually grows somewhat, unlike modern mysticetes where they do not grow after birth. In the periotic, the hole for the facial nerve increases in diameter, perhaps corresponding to the increase in length of the palate, jaws, and the tongue - which the facial nerve innervates. From Boessenecker and Fordyce (2015a).

More on growth in Waharoa: the rostrum lengthens considerably during postnatal (e.g. after birth) growth in eomysticetids. Modern balaenopterid whales have long snouts, but they're nearly the same proportion at birth. Eomysticetids have a considerably steeper rate of rostral growth relative to other mysticetes. This strongly suggests that the length of the rostrum is critical in feeding, and the process of acceleration is likely responsible, but to a greater degree than in balaenopterid whales. From Boessenecker and Fordyce (2015a).

Two other genera were uncovered by Fordyce's field work that were completely undetected by Marples' efforts. One of these new taxa consisted of three skulls - the "Earthquakes" eomysticetid, the Haugh's quarry eomysticetid, and the "Springside cleft" juvenile mysticete - a species somewhat more delicately built than Tokarahia or Tohoraata, with smaller earbones and a narrower skull. We named this Waharoa ruwhenua - the species name here is a bit of word play. The fossil locality is called "The Earthquakes", since the way the rocks of the Otekaike Limestone have been exposed and weathered, it looks like a cartoon rift in the ground. Ruwhenua in Maori translates to "shaking land" - the Maori word for an earthquake. Waharoa means 'long mouth', referring to the exceedingly long palate and mandible of the main specimen. Specimens of Waharoa provide some insights into the feeding morphology and growth of eomysticetids, and early mysticetes in general. There are some tooth socket like structures in two of the specimens, suggesting a handful of vestigial peg-like teeth, as potentially preserved in Tokarahia. The palate has a number of palatal foramina, strongly suggesting the presence of baleen. However, these foramina are not present at the very front of the mouth, suggesting a gap in the baleen and perhaps a skim feeding behavior like modern right whales. The growth series of Waharoa ruwhenua includes a perinatal individual likely only a few months old at the very most, a somewhat larger juvenile, and an adult - confirmed through bone histology. The growth series indicates that the rostrum and palate grow rapidly during growth, and that juveniles are born with relatively shorter snouts, with the snout growing much more rapidly than in any modern mysticete. Similarly, one of the various holes in the earbones - the canal for the facial nerve - increases in diameter during growth. The facial nerve innervates the tongue, so it's possible that the nerve increases in diameter to innervate a much larger tongue in later life.

The highly bioeroded skull of the Waihao river eomysticetid - the holotype of Matapanui waihao. Note how the middle section of the right mandible was bioeroded away, but each end stayed in its approximate location; the braincase, and posterior end of the left mandible, were reoriented by currents after considerable bioerosion by bone eating worms (Osedax). From Boessenecker and Fordyce (2017a).

The well-preserved right periotic of Matapanui waihao. The left one was accidentally sawn through with a masonry saw during the excavation. "C'est la vie" Ewan said, when he shared that with me. From Boessenecker and Fordyce (2017a).

The left tympanic bulla of Matapanui waihao, with the posterior process in articulation (held in place with clay). From Boessenecker and Fordyce (2017a).

The last eomysticetid from my thesis was Matapanui waihao - originally named Matapa waihao, but the genus name was preoccupied by a genus of butterflies from Sri Lanka. So, we quickly renamed it Matapanui - translating to "big flat face" in Maori (Boessenecker and Fordyce, 2017c). The species name is after the Waihao river where it was collected (NOT the Waihao greensand!). This species was based off of specimens from the Kokoamu Greensand, and the type specimen is the oldest eomysticetid from New Zealand, dating to the Whaingaroan stage - approximately 28-27 Ma, though only 1-2 million years older than Tokarahia and Tohoraata. Matapanui has a somewhat longer and more 'square' supraorbital process of the frontal that is dorsally quite flat, and a curved rather than pointed apex of the occipital shield. The earbones are quite distinctive, with a proportionally large 'cochlea' (to be specific, the cochlear portion of the periotic). Several specimens were collected in parallel, including a fragmentary specimen from Sisters Creek consisting of a skull fragment, periotic, and partial atlas vertebra, and a partial braincase of a much more mature individual with fragmentary periotic from either the Potikohua Limestone or the Tiropahi Limestone from an underground limestone exposure in Te Tahi Cave on the west coast of the South Island, with poor age control. One of Ewan's students reported the specimen embedded in the side of the cave, and Ewan went spelunking - and wrapped up the braincase in his coat. Based on this fragmentary specimen, Matapanui was likely the largest and most robust of all of the NZ eomysticetids.

A fragmentary juvenile eomysticetid with a distinctive mandible: the end is blocky and curved dorsally, two traits otherwise known only in Yamatocetus from Japan. We proposed that this specimen from the Otekaike Limestone indicated that Yamatocetus had an antitropical distribution in the western Pacific. From Boessenecker and Fordyce (2017b).

The semi-controversial specimen OU 22744 from the "Protula bed" of the uppermost Otekaike Limestone at Hakataramea quarry, which we identified as cf. Waharoa based on the morphology of the atlas vertebra. From Boessenecker and Fordyce (2017b).

Ewan and I reported a couple more eomysticetids in a rather short paper published in 2017. This final paper from my Ph.D. research reported a tentatively identified specimen of Yamatocetus from New Zealand, consisting of a fragmentary braincase associated with distinctive mandibles. The anterior tips of the mandibles were squared, unlike the spear-shaped profile of Tokarahia, Waharoa, and probably Matapanui, and also dorsally curved at their anterior tips - a combination of features only known in the Japanese eomysticetid Yamatocetus canaliculatus. This specimen suggests that Yamatocetus had an antitropical distribution in the western Pacific - e.g. living in both the northern and southern parts of the western Pacific, and likely the only eomysticetid with an antitropical distribution at the genus level. The second specimen was tentatively identified as Waharoa based on the similar morphology of the atlas vertebra, and is a relatively fragmentary postcranial skeleton from near the top of the Otekaike Limestone; we identified the specimen as cf. Waharoa, and owing to its stratigraphic position, it is the only eomysticetid that appears to have dated to the earliest Miocene; indeed, the horizon the specimen is from a horizon dated to 22.8-22.3 Ma, but that has recently been revised (see below). A review paper on the fossil record of New Zealand Eomysticetidae was published by Marcus Richards and I (2024) in the Fossil Vertebrates from Zealandia special volume of the Journal of the Royal Society of New Zealand, wherein we briefly summarize what we know and what the major contributions of the fossil assemblage were, in addition to figuring a couple of recently discovered (and rediscovered) specimens.

Revised Geochronology of latest Oligocene mysticetes from the Otekaike Limestone

A new study by Felix Marx et al. (2024) published in the same special volume of the JRSNZ on fossil vertebrates from Zealandia provides a slate of new Strontium isotope dates for sixteen of the mysticete (and some odontocete) specimens from the Otekaike Limestone. Strontium isotopes have varied naturally in seawater since the Cambrian, with the curve going up and down - and the curve, specifically, being formed by the ratio of Strontium 87 and 86. Both are stable isotopes (e.g. they don't undergo radioactive decay, though 87Sr is radiogenic in origin, decaying from Rubidium 87). Differences in what rocks are weathering out at the earth's surface result in changes to the ratio of 87Sr versus 86Sr, with peaks and valleys through time, but generally since the Cretaceous getting more enriched in 87Sr. In many periods of earth's history, (especially the Cenozoic) the line is steep enough that if you get a new ratio, you can get quite a good date from it - in this study, and thanks to the steepness of the curve during the Oligocene, the error can be as small as +/- 100,000-200,000 years. But, you need relatively robust, unaltered marine invertebrate shells to grind down into a powder and analyzed with an X-ray diffractor. For this study, they used Lentipecten shells - relatively robust scallop shells measuring up to about 1-2 mm in thickness and about 7-9 cm across. At Haugh's quarry, these would sometimes pop out of the limestone free of matrix, and we would unceremoniously throw these at each other like frisbees. Ewan Fordyce had a habit of keeping matrix and associated invertebrates found during the excavation and preparation of fossil cetaceans, and in this case, permitted quite a few specimens to be dated isotopically.

The record of eomysticetids and Mauicetus-Horopeta grade mysticetes from New Zealand and beyond: New Zealand has some of the only known fossil mysticetes from the earliest Miocene, making the collection at Otago one of the globally most important for studying this "dark age" in mysticete evolution. From Marx et al. (2024).

All sampled eomysticetids from the Otekaike Limestone, save one (keep reading) were found to be squarely in the Oligocene, with ages of around 25-24 Ma - slightly younger than originally considered, as some of these were thought to be Duntroonian in age, which is about 27-25 Ma; most of these all seem to be Waitakian (25-23 Ma) instead. As for the specimen that Ewan and I reported that we considered, at the time, to be an earliest Miocene eomysticetid? Marx et al. (2024) think that that specimen is actually some sort of Mauicetus-like mysticete. We were appropriately circumspect about the identification of that specimen as cf. Waharoa, based chiefly on the atlas morphology - but more recently collected Mauicetus-like specimens, including a monolith of a jacket we excavated in 2013, preserve similarly humongous, robust atlases that challenge our identification. Further, if the specimen does turn out to be an eomysticetid, the date on the specimen is somewhat older than we initially thought based on its stratigraphic position relative to the "Protula Bed" in Haugh's quarry, which suggested it was about a meter into the Miocene - instead, the date is 23.08 Ma, just slightly older than the Oligocene-Miocene boundary at 23.03 (though perhaps splitting hairs here, given that the error on this measurement is +/- 0.5 million years).

In sum, this study clarifies that there does seem to be an absence of eomysticetids from the uppermost part of the Otekaike Limestone; the upper ten or 15 meters, generally representing strata immediately at/around the Oligocene-Miocene boundary, appear to only represent Mauicetus-like taxa. There don't appear to be any of the strange mysticetes like "Tsai's whales" - e.g. Horopeta, Whakakai, and Toipahautea - most of these are from the Kokoamu Greensand, or near the base of the Otekaike Limestone. This study also raises the possibility that a couple of the marker beds we've used to identify the base of the Duntroonian might be slightly younger than originally thought, or that the Otekaike Limestone is time-transgressive. Most critically, is that it apparently demonstrates the extinction of the Eomysticetidae just before the Oligocene-Miocene boundary, leading into the Aquitanian baleen whale gap, documented well a few years earlier by Marx et al. (2019).

New Zealand fossil mysticetes and the origin of Crown Mysticeti

One thing is certain - New Zealand boasts, by a very wide margin, the greatest diversity of toothless/baleen-bearing mysticetes in the world during the Oligocene epoch. There are to date approximately six eomysticetids, three of "Tsai's whales" (and at least 1-2 additional unnamed species), Mauicetus parki, the ZMT 67 taxon (either Mauicetus or a closely related genus), a possible balaenoid represented by specimen OU 22224, and likely a couple of others - ballpark, around 12-15 species for the late Oligocene (Chattian stage; e.g. Duntroonian to Waitakian) and earliest Miocene (e.g. ZMT 67 is from the first million years of the early Miocene Aquitanian stage) alone. This sort of diversity is absurd - and, while not all of these species are present at the same horizon, at least half of them are if one takes a look at the Kokoamu Greensand, for example. Further to the point, according to the careful work of Marx et al. (2023), the eomysticetids tend to be lower down stratigraphically and do not temporally overlap with true Mauicetus-type fossils, suggesting some faunal change within the region. In addition to the sheer diversity, New Zealand also boasts the majority of the entire fossil record of Oligocene baleen-bearing mysticetes; there are between fifteen and twenty eomysticetid skulls from Japan, Washington, Oregon, Baja California, South Carolina, and Europe - combined - and at least that many eomysticetid skulls from New Zealand, plus at least that approximate number of whales in the Mauicetus and "Tsai's whales" grade. I would wager that New Zealand boasts something like half or two thirds of the fossil record of Oligocene chaeomysticetes.

The referred juvenile skull of Mauicetus parki - this specimen revealed a far more derived looking skull than Benham ever anticipated, and certainly one that would not have surprised Kellogg, for it greatly resembles Parietobalaena - but is much, much older (~23 Ma v. 16 Ma). From Tsai (2024).

A review paper by my PhD colleague and dear friend Cheng-Hsiu Tsai (2023) in the same special volume of the JRSNZ considers this to be likely evidence that crown Mysticeti - the group formed by modern baleen whales and their most recent common ancestor - likely evolved in the southern hemisphere. Tsai points out that whales in the Topiahautea-Whakakai-Horopeta complex (which I've informally called "Tsai's whales" in this blog post) have, so far, really only been found in New Zealand, and further suggests that niche partitioning was likely in effect to permit this unusual degree of diversity. Further to the point, 'toothless' mysticete "assemblages" from the North Pacific and North Atlantic tend to consist of only a single species of eomysticetid: Sitsqwayk and Maiabalaena are both from the Pacific Northwest, but are from different stratigraphic units and not contemporaneous; Yamatocetus is the only 'toothless' mysticete from the Ashiya Group of Japan; and Eomysticetus and Micromysticetus are both found in Charleston, South Carolina, but are found in the Chandler Bridge Formation and underlying Ashley Formation (respectively) and separated in time by about ~4-5 million years. Charleston rivals New Zealand for Oligocene cetacean sampling - and certainly suprasses it in terms of the odontocete assemblage, perhaps three or fourfold (there are between 50 and 80 skulls, versus perhaps one or two dozen from NZ) - but there are only about a half dozen quasi-complete 'toothless' mysticete skulls that have ever been found in Charleston (as opposed to many, many dozens of odontocetes) and they are all eomysticetids (save one, see below).

The skull of Tlaxcallicetus from the Oligocene of Baja California. From Hernandez-Cisneros (2018).

There are a few tantalizing possibilities of "Tsai's whales" being found elsewhere: I strongly suspect that Tlaxcallicetus, named by our Mexican colleague Ehecatl Hernandez-Cisneros a few years ago, may be one of these whales; the periotic is quite strange. There's a fragmentary periotic in a squamosal chunk I acid prepared from the Pysht Formation that looks like Whakakai, and is clearly not an eomysticetid, but it is in bad shape. And lastly, there is a Horopeta-like juvenile braincase I excavated from the ~30 myo Ashley Formation in South Carolina back in 2018 or so, and it remains unstudied. But, these are unconfirmed identifications and I don't put much stock in them for the time being. Even if these are accepted, they barely inflate diversity elsewhere (raising the number to 2 or perhaps 3 baleen-bearing mysticetes) and likely represent diversity 'exported' from the south. Tsai (2023) contrasts these whales, which he terms the Toipahautea-Mauicetus grade, with eomysticetids by highlighting that eomysticetids likely diversified earlier in the Oligocene, having already dispersed to all corners of the globe by the mid Oligocene. On the other hand, "Tsai's whales" and Mauicetus are found only locally, and again, are surprisingly diverse - suggesting that the NZ fossil record is preserving an 'in situ' radiation. He concludes that

One last study requires discussion, and this is analysis of the "baleen whale gap" reported by Marx et al. (2019). This study examined a wide sampling of baleen whale earbones from the Oligocene and early Miocene of New Zealand and Australia, including toothed mysticetes, along with global trends in Oligo-Miocene mysticete diversity. They found that in the more coastal deposits of Australia, the fossil record of mysticetes were dominated by small toothed mysticetes in the Mammalodontidae, which made up about 82% of the fossils altogether; 15% were eomysticetids, and only 3% were non-eomysticetid true mysticetes - e.g. Mauicetus-like species of possible records of "Tsai's whales". In New Zealand, which they considered to represent more pelagic conditions given the near-submergence of Zealandia (see first post) and the remoteness of the Zealandia shelf, the fossil assemblage is instead dominated by baleen-bearing mysticetes with non-eomysticetid mysticetes comprising a staggering 73% of the assemblage, mammalodontids only about 4%, and eomysticetids at 23% of the fauna.

Comparison of mysticete assemblages from the Oligocene of Australia (A1, B1) and New Zealand (A2, B2). Eomysticetids are similarly uncommon in both regions, but the real difference lies in toothed mysticetes and "Tsai's whales" - aka "other Chaeomysticeti" here. The former - mammalodontids - dominate the Australian record, whereas they are very rare in New Zealand, which is dominated by these "other Chaeomysticeti" - mostly members of the Mauicetus-Horopeta grade, aka "Tsai's whales" elsewhere in this post. From Marx et al. (2019).

Marx et al. (2019) infer a 'dark age', or as I call it, a baleen whale gap during the first five million years of the Miocene. We know they clearly survived, but baleen whale fossils are astonishingly rare during the Aquitanian stage and earliest Burdigalian, only becoming common again around 17-18 mya. All early Miocene mysticetes known from the Aquitanian are relatively derived species that some of us have informally called "Kelloggitheres" - also slightly less informally referred to as "cetotheres" sensu lato, stem balaenopteroids, or stem thalassotheres. I'll keep using "Kelloggitheres" as the term was devised in an SVP talk years ago by Erich Fitzgerald, in honor of Remington Kellogg, who worked on a ton of these sorts of whales from the Miocene of Maryland/Virginia, California, South America, and Oregon; these are species like the well-known Parietobalaena and Diorocetus from the Calvert Formation of Maryland. Mauicetus parki in particular shares a lot in common with these, differing chiefly in having a somewhat more archaic set of earbones and vertex, and I would argue, is the first "Kelloggithere". One thing I've noticed is that these species are all remarkably similar, and given that aside from the early right whale Morenocetus, virtually all early Miocene mysticetes have "Kelloggithere" affinities, these species are probably extremely oversplit and are in dire need of revision. As a result of this, anatomical diversity - a metric frequently called 'disparity' - tanks during the early Miocene, reflecting the fact that these are all very similar looking whales with very slight variations on a theme.

What explains the extinction of toothed mysticetes and eomysticetids at the end of the Oligocene, and the ensuing global rarity of crown mysticetes during the Aquitanian stage (earliest Miocene, 23-20 Ma)? Marx et al. (2019) suggest that a cooling event may have resulted in a temporary collapse of shallow marine food webs. The "other Chaeomysticeti" during the Oligocene are really only known from New Zealand, which they hypothesize to mean that these whales were much more pelagic, explaining their absence from Australia. Later, pelagic mysticetes would end up diversifying and once again be found as fossils in shallow marine environments starting in the Burdigalian stage (late early Miocene, ~17-20 Ma). From Marx et al. (2019).

Marx et al. (2019) correlate the extinction of toothed mysticetes and eomysticetids with a brief but drastic cooling period coinciding with a drop in sea level at the end of the Oligocene, which may have driven faunal collapse in coastal marine settings, leading to the extinction of decidedly shallow marine toothed mysticetes like the mammalodontids. Likewise, there was a crash in global diatom abundance in the earliest Miocene, which may have led to globally reduced biomass of zooplankton. They hypothesized that the whales which seemed to have survived are those from New Zealand with a more pelagic (open ocean) habitus - perhaps explaining their rarity in continental shelf deposits elsewhere for several million years. During this 'dark age', baleen whales were possibly pelagic only and likely to be numerically quite rare - only diversifying once again as climate, primary productivity, and planktonic diversity all increased during the Middle Miocene Climatic Optimum around 15 mya. Curiously, there is a potential early Miocene extinction event recorded in pelagic shark fossils around 18 mya by Elizabeth Sibert and colleagues (2021; covered in an earlier blog post, read it here), and Tsai (2024) suggests that this may be related to the baleen whale 'dark age'. I am tempted to agree, though the baleen whale record tanks several million years prior.

As always, there is more yet to do: all of these jackets in the University of Otago basement contain fossil cetaceans, chiefly from the upper Otekaike Limestone at Hakataramea Quarry (and are therefore about 22-25 Ma), and few have been prepared. Each one potentially represents a future holotype or a referred specimen of an existing species that might shed critical light on the functional anatomy and evolution of the earliest crown mysticetes. From Tsai (2023).

Cheng-Hsiu Tsai in the final stages of his Ph.D. research in late 2014, with dozens of fossil (and modern) mysticete earbones. The specimens in the foreground are mostly eomysticetids he had borrowed from my office, since I was largely done with describing and photographing them at this stage. Photo by me.

Regardless, we have a lot more to learn - even just from the collections of the University of Otago. Tsai (2024) points out that many of these early mysticetes are known within the Fordyce lab, past and present - but formally, many such specimens are only known as a trail of breadcrumbs in SVP abstracts and mentions in various papers. One such specimen is the "Oligocene right whale", OU 22224 - a mysticete close to the ancestry of Crown Mysticeti. This specimen has a vertical occipital shield and an arched rostrum - resulting in its identification as a possible Oligocene balaenid. If the identification holds, it would be the oldest known crown mysticete, and certainly the oldest member of any modern family. However, it frequently plots out amongst "Tsai's whales" - within the Toipahautea-Mauicetus complex, though in the most recent phylogeny by Tsai and Fordyce (2018), it did plot out as a sister taxon to the Balaenidae. We'll have to await study of the specimen - but aside from this, there are many other unpublished mysticetes known from partial braincases, fragmentary skulls, nearly complete skulls, and most that have been excavated in recent years seem to be Mauicetus-like whales. Recently, for example, the enormous, nearly 3 meter long jacket we nicknamed the "star destroyer" has been prepared and photos shared with me; it looks to be a large whale close to Mauicetus and ZMT 67 in its morphology. There are untold treasures awaiting study in the Otago collection - Fordyce's collecting over the past 40 years will keep us busy for decades.

Some new specimens preliminarily reported in my paper with Marcus Richards earlier this year: A new specimen of Tokarahia (C-D) and Matapanui (I), along with the identification of a partial skull (E-G) that is probably associated with a Matapanui waihao periotic (H) that were separated many years prior to my arrival in New Zealand, with the specimen sheets misplaced. This new rostrum of Matapanui (E-G) has some of the most finely preserved palatal foramina present in any eomysticetid, clearly indicating that eomysticetids in general had baleen. From Boessenecker and Richards (2024).

Three new eomysticetid specimens have either been freshly prepared or were collected entirely after my time at Otago. The first is OU 22473, the periotic of which I had described in 2017 as a specimen of Matapanui waihao. A partial skull (OU 22120) was possibly associated - however, the periotic was separated from the skull after preparation by the late preparator Andrew Grebneff and for a long while it was unclear if the partial skull really belonged. Ewan recalled a white periotic being associated with the block, and this unlabeled specimen seemed to fit the bill - as the only good candidate, we always assumed they were the same specimen. However, short of being able to demonstrate it, we cautiously assigned a new number for the periotic. A while after I left, preparator Sophie White conducted some more preparation of the skull - the skull was in a block of limestone that cracked horizontally right through the rostrum. On one block is the supraorbital process, one mandible, and the base of the rostrum, with the dorsal surface prepped out; on the other block is the ventral surface of the rest of the rostrum. While not prepared completely, the new prepwork showcases the palatal foramina quite beautifully - clearly demonstrating that eomysticetids, when well-preserved, do indeed have an extensive network of vascular channels for the arteries and nerves that feed the baleen. Likewise, it means that if specimens like the holotype skull of Maiabalaena - once championed as evidence that eomysticetids had neither baleen nor teeth - were better preserved, they would likely show something similar. But, you really do need specimens with well-preserved (and well-prepared) palates to make such claims. The other two specimens are more fragmentary. One, OU 22783, is a partial skull with periotic of Tokarahia; it preserves a partial rostrum, posterior mandible, and braincase. The other is the Smite River whale, OU 22028, is another specimen of Matapanui sp., with an even more fragmentary mandible, braincase, and partial periotic. These specimens have been figured and briefly outlined, but I'll have to make it back down to Dunedin sometime to get these specimens written up!

On that note, onto part three - fossil odontocetes from New Zealand, Ewan's true passion.

References

Benham, W. B. (1937). Fossil Cetacea of New Zealand II. - On Lophocephalus, a new genus of zeuglodont Cetacea. Transactions of the Royal Society of New Zealand, 67, 1-7.

Benham, W. B. (1942). Fossil Cetacea of New Zealand V. - Mauicetus, a generic name substituted for Lophocephalus Benham. Transactions of the Royal Society of New Zealand, 71, 260-270.

Boessenecker, R. W., & Fordyce, R. E. (2015a). Anatomy, feeding ecology, and ontogeny of a transitional baleen whale: a new genus and species of Eomysticetidae (Mammalia: Cetacea) from the Oligocene of New Zealand. PeerJ, 3, e1129.

Boessenecker, R. W., & Fordyce, R. E. (2015b). A new eomysticetid (Mammalia: Cetacea) from the late Oligocene of New Zealand and a re-evaluation of 'Mauicetus' waitakiensis. Papers in Palaeontology, 1(2), 107-140.

Boessenecker, R. W., & Fordyce, R. E. (2015c). A new genus and species of eomysticetid (Cetacea: Mysticeti) and a reinterpretation of "Mauicetus" lophocephalus Marples, 1956: transitional baleen whales from the upper Oligocene of New Zealand. Zoological Journal of the Linnaean Society, 175, 607-660.

Boessenecker, R. W., & Fordyce, R. E. (2017a). A new eomysticetid from the Oligocene Kokoamu Greensand of New Zealand and a review of the Eomysticetidae (Mammalia, Cetacea). Journal of Systematic Palaeontology, 15(6), 429-469.

Boessenecker, R. W., & Fordyce, R. E. (2017b). Cosmopolitanism and Miocene survival of Eomysticetidae (Cetacea: Mysticeti) revealed by new fossils from New Zealand. New Zealand Journal of Geology and Geophysics, 60(2), 145-157.

Boessenecker, R. W., & Fordyce, R. E. (2017c). Matapanui, a replacement name for Matapa Boessenecker & Fordyce, 2016. Journal of Systematic Palaeontology, 15, 471.

Boessenecker, R. W., & Richards, M. D. (2024). A review of New Zealand Eomysticetidae (Mammalia, Cetacea) and implications for the evolution of baleen whales: new specimens, functional anatomy, and phylogeny. Journal of the Royal Society of New Zealand, 54, 696-710.

Clementz, M. T., Fordyce, R. E., Peek, S. L., & Fox, D. L. (2014). Ancient marine isoscapes and isotopic evidence of bulk-feeding by Oligocene cetaceans. Palaeogeography, Palaeoclimatology, Palaeoecology, 400, 28-40.

Corrie, J. E., & Fordyce, R. E. (2022). A redescription and re-evaluation of Kekenodon onamata (Mammalia: Cetacea), a late-surviving archaeocete from the late Oligocene of New Zealand. Zoological Journal of the Linnaean Society, 196, 1637-1670.

Corrie, J. E., & Fordyce, R. E. (2024). A new genus and species of kekenodontid from the late Oligocene of New Zealand with comments on the evolution of tooth displacement in Cetacea. Journal of the Royal Society of New Zealand, 54, 722-737.

Davis, J. W. (1888). On fossil fish-remains from the Tertiary and Cretaceo-Tertiary Formations of New Zealand. Scientific Transactions of the Royal Dublin Society, 4, 1-62.

Fordyce, R. E. (1985). Late Eocene archaeocete whale (Archaeoceti: Dorudontinae) from Waihao, South Canterbury, New Zealand. New Zealand Journal of Geology and Geophysics, 28, 351-357.

Fordyce, R. E. (1989). Problematic early Oligocene toothed whale (Cetacea, ?Mysticeti) from Waikari, North Canterbury, New Zealand. New Zealand Journal of Geology and Geophysics, 32(3), 395-400.

Fordyce, R. E. (2005). A new specimen of archaic baleen whale Mauicetus parki (Late Oligocene, New Zealand) elucidates early crown-Mysticeti. Journal of Vertebrate Paleontology, 25, supplement to number 3, 58A.

Fordyce, R. E. (2006). An unexpected diversity of basal baleen whales: Late Oligocene Eomysticetidae from New Zealand. Journal of Vertebrate Paleontology, 26, supplement to number 3, 62A.

Fordyce, R. E., & Hiller, N. (2014). An associated skeleton of juvenile late Eocene basilosaurid archaeocete from New Zealand. Journal of Vertebrate Paleontology, 34, 131A.

Fordyce, R. E., & Marx, F. G. (2016). Mysticetes baring their teeth: a new fossil whale, Mammalodon hakataramea, from the southwest Pacific. Memoirs of Museum Victoria, 74, 107-116.

Glaessner, M. F. (1972). Redescription of the tooth of an Oligocene whale from North Canterbury, New Zealand. Records of the Canterbury Museum, 9, 183-187.

Hector, J. (1881). Notes on New Zealand Cetacea, recent and fossil. Transactions of the New Zealand Institute, 13, 434-436.

Kellogg, R. (1936). A review of the Archaeoceti. Carnegie Institution of Washington Publication, 482, 1-366.

Keyes, I. W. (1973). Early Oligocene squalodont cetacean from Oamaru, New Zealand. New Zealand Journal of Marine and Freshwater Research, 7, 381-390.

Köhler, R., & Fordyce, R. E. (1997). An archaeocete whale (Cetacea: Archaeoceti) from the Eocene Waihao Greensand, New Zealand. Journal of Vertebrate Paleontology, 17, 574-583.

Marples, B. J. (1956). Cetotheres (Cetacea) from the Oligocene of New Zealand. Proceedings of the Zoological Society of London, 126, 565-580.

Marx, F. G., Coste, A., Richards, M. D., Palin, J. M., & Fordyce, R. E. (2024). Strontium isotopes reveal a globally unique assemblage of early Miocene baleen whales. Journal of the Royal Society of New Zealand, 54, 711-721.

Marx, F. G., Fitzgerald, E. M. G., & Fordyce, R. E. (2019). Like phoenix from the ashes: how modern baleen whales arose from a fossil "dark age". Acta Palaeontologica Polonica, 64(2), 231-238.

Marx, F. G., & Fordyce, R. E. (2015). Baleen boom and bust: a synthesis of mysticete phylogeny, diversity and disparity. Royal Society Open Science, 2, 140434.

Mitchell, E. D. (1989). A new cetacean from the late Eocene Meseta Formation, Seymour Island, Antarctic Peninsula. Canadian Journal of Earth Sciences, 46, 2219-2235.

Raine, J. I., Beu, A. G., Boyes, A. F., Campbell, H. J., Cooper, R. A., Crampton, J. S., . . . Morgans, H. E. G. (2012). New Zealand Geological Timescale v.2012/1. Lower Hutt, New Zealand: GNS Science.

Thompson, N. K., Bassett, K. N., & Reid, C. M. (2014). The effect of volcanism on cool-water carbonate facies during maximum inundation of Zealandia in the Waitaki-Oamaru region. New Zealand Journal of Geology and Geophysics, 57, 149-169.

Tsai, C.-H. (2024). In search of the origin of crown Mysticeti. Journal of the Royal Society of New Zealand, 54, 682-695.

Tsai, C.-H., & Fordyce, R. E. (2015). The earliest gulp-feeding mysticete (Cetacea: Mysticeti) from the Oligocene of New Zealand. Journal of Mammalian Evolution, 22, 535-560.

Tsai, C.-H., & Fordyce, R. E. (2016). Archaic baleen whale from the Kokoamu Greensand: earbones distinguish a new late Oligocene mysticete (Cetacea: Mysticeti) from New Zealand. Journal of the Royal Society of New Zealand, 46, 117-138.

Tsai, C.-H., & Fordyce, R. E. (2018). A new archaic baleen whale Toipahautea waitaki (early Late Oligocene, New Zealand) and the origins of crown Mysticeti. Royal Society Open Science, 5(172453).

Uhen, M. D. (2013). A review of North American Basilosauridae. Alabama Museum of Natural History Bulletin, 31(2), 1-45.

The fossil record of early cetaceans from New Zealand, 1: introduction, archaeocetes, and toothed mysticetes

2025-12-08T03:00:00.000-08:00

This is part 1 of the fossil record of early cetaceans of New Zealand, with an introduction to the stratigraphy and geology, and the archaeocetes and toothed mysticetes from NZ. For toothless baleen whales, see part 2 here, and for "dolphins" (Odontoceti), see part 3 here (out next Monday!).

The holotype teeth and earbones of Kekenodon onamata - one of the earliest named fossil cetaceans from New Zealand, and by far the most consistently enigmatic. From Hector (1881).

New Zealand is a special place - a rainy, lush, cold island nation in the south Pacific. A veritable lost world - when the first Polynesians arrived around 1300 CE, the island was populated by gigantic birds. When Europeans (Pakeha) first "discovered" New Zealand, the Maori oral tradition was so strong that there were still names for these - the moa - despite having been driven to extinction centuries before. The bird fauna and plant flora are still very distinctive, despite disappearance of many of the larger species. New Zealand is just the exposed portion of the landmass Zealandia - technically a microcontinent. However, it's the largest of these, and also known as the "eighth continent" owing to its size: it's half the size of Australia, and more than six times the area of the second largest 'microcontinent', Madagascar. Most of Zealandia is underwater - about 94% - yet composed of light, silica rich continental crust that just happens to be mostly submerged, forming broad swathes of shallow continental shelf that is considerably shallower than the abyssal plain surrounding it. Other well-known islands that are parts of Zealandia include the Chatham Islands east of Dunedin, Stewart Island south of Invercargill, New Caledonia, Norfolk Island, and nearly 700 additional islands in the region.

New Zealand, that part of the world frequently left off of world maps! While few are familiar with New Zealand other than "it's near Australia, I think", the lost continent of Zealandia - here outlined in pink - is even less well known to the public. All of that shallow continental shelf is continental crust, a large chunk of Pangea that rifted apart - it's about 2/3 the land area of Australia, and also includes New Caledonia. Image credit: NOAA via Wikimedia.

New Zealand has also been largely submerged for much of its history - resulting in a fantastic marine fossil record that is nearly continuous from the late Cretaceous to the Pleistocene. Part of this marine record - the Oligocene epoch - led me to move to Dunedin with my wife Sarah in 2012 and begin my Ph.D. research on fossil whales with Dr. Ewan Fordyce in the Geology Department at the University of Otago. Much of the information I'll be covering in these posts is either based on fossils discovered by Ewan or published or otherwise studied by him and his students. Sadly, Ewan passed away in November 2023. I've decided to restrict this post to the Eocene and Oligocene record of archaeocete, mysticete, and odontocete fossils from the country, and may delve *a little* into the early Miocene - the fossil record of cetaceans from the mid-late Miocene and Pliocene is much more spotty, and the real "meat" is in the "middle" Cenozoic - approximately 40-20 million years ago. Furthermore, virtually all of these fossils are from the South Island, and specifically the southern Canterbury Basin in the vicinity of Oamaru - chiefly the Waitaki Valley and the Hakataramea Valley.

Some notes on Maori (and Polynesian) pronunciation

New Zealand is notable for being the southwestern tip of the Polynesian triangle - defined as all the islands and waters between New Zealand, Hawaii, and Rapa Nui (aka Easter Island). Maori (pronounced Maw-ri - not Mow-ri, e.g. not rhyming with 'Now') is not too dissimilar from Hawaiian or Tongan, or Tahitian* for that matter. Many of the words are very similar - for example, in Maori a 'k' would be present where in Hawaiian there would be a 't' - famous Waikiki beach would become Waititi, which happens to be the last name of the critically acclaimed director Taiika Waititi (who was still very much a local phenomenon when we were there, mostly showing up in a bunch of hilarious beer commercials).

*The 'a' in many Polynesian words is typically pronounced longer than we think if we were reading English words. Tahiti and Samoa are not "tuh-heetee" or "suh-mo-uh" but "taw-hee-tee" and "saw-moe-uh". On a family trip to Oahu in 2001 I recall learning this at the Polynesian cultural center, and the memory of it jolted back into my brain after a few days in Dunedin. To alleviate this, when you're actually in New Zealand, the 'long A' is usually identified with a macron.

The Polynesian Triangle. When most folks think about Polynesia, tropical paradises like Tahiti and Hawaii come to mind - but it also includes New Zealand, which is the furthest south and the coldest climate that Polynesians colonized. 1) Hawaii; 2) Aotearoa/New Zealand; 3) Rapa Nui/Easter Island; 4) Tonga & Samoa; 5) Tahiti. Image credit: Kahuroa via Wikimedia commons.

What's really impressive is that Polynesia was settled so rapidly and efficiently that the language has barely had any time to change - the Polynesian settling of the south Pacific started around 700 AD with their arrival in the Marquesas, Cook islands, and Tahiti; by 800-900 arriving in Samoa, Hawaii, and Tonga, and around 1000-1200 Rapa Nui (Easter Island), and lastly, exploring south and settling Aotearoa (New Zealand) by 1200 (Moa became extinct by around 1450). Contact with westerners like the Dutch explorer Abel Tasman did not occur until the 17th century (though the Spanish and Portugese made contact with the peoples of Melanesia and Micronesia further to the north, e.g. Guam, during the prior century). Captain James Cook landed in Tahiti and Tupaia, a Tahitian 'priest' of sorts, befriended the chief botanist of the expedition, Joseph Banks (who would later become the most influential president of the Royal Society), and joined the expedition. His story is remarkable - trained as a star navigator, from memory, he was able to correctly map out at least 134 islands within 2000 miles and provide the names of at least 70 of them. However, the most remarkable - and relevant - part of the story here is that once arriving in New Zealand a few months later in October 1769 - over 4,000 kilometers away - Tupaia was able to speak with the Maori and have mutually intelligible conversations. Like anywhere else in Polynesia, there were of course some dialect differences, but the recent and rapid colonization of Polynesia meant that the language is surprisingly similar over vast differences - no doubt stabilized by continuous maritime trade and voyages between islands (on Tupaia's map, for example, he indicated that he had personally visited at least 13 of the islands, and that his ancestors had visited all of them, except for an island north of Fiji, and Oahu. Anyway, there's a fabulous book titled Voyagers by Nicholas Thomas that goes into the rich history of the Polynesian colonization of the Pacific.

Now, onto some pronunciation (and take this with a grain of salt as even Pakeha living in NZ for three years cannot do a great job pronouncing everything properly):

The 'r' in Maori words is typically rolled, slightly - but not so extravagantly as in Spanish.

'i' is always an 'eee' sound.

'wh' in the South Island dialect is, strangely, pronounced as an 'f' - this is likely due to a bad translation error made by Pakeha (foreigners) in the late 19th century. Because all of the fossil cetaceans from NZ are based on fossils from the South Island, the 'wh' is always pronounced as an 'f'. So - the species name for the dolphin Waipatia maerewhenua? That's 'mare-reh-fen-you-uh'. In various North Island dialects, wh sounds identical to w.

T is always hard. Waipatia might be spelled like the name of the Hellenic scholar Hypatia, but the -tia is not pronounced 'sh'.

There are a ton of dipthongs in Maori:

'ai' is pronounced like I, e.g. 'Wai' is "why".

'ae' is pronounced like 'ai' in English, e.g. the way you would pronounce 'air', 'fair', or 'hair'.

'ua' is pronounced 'you-uh'

'ui' is pronounced 'you-eee'

'oi' is 'oy', so if you

'au' is a difficult one, but sounds like 'oh'.

'ou' is pronounced more like 'ooo'.

'eo' is pronounced 'eyyy-oh'

I'm sure I've missed some, but if you're wanting to learn more, check out resources like this: https://www.maorilanguage.net/how-to-pronounce-maori/.

Now, one major wrinkle to learning Maori pronunciation is that you have to do it while learning New Zealand pronunciation of English, which is barely English. It was one thing speaking with Fordyce at conferences in the USA and Canada, despite his very distinctive accent - he knew to use American words rather than their 'kiwi' counterparts. This kindness left me more or less completely unprepared while ordering food, drinks, taxis, etc. while speaking with New Zealanders. Ironically, exposure to Tongan accents in high school and visits to Hawaii meant that I didn't find Maori accents too difficult, but good lord, it was tough understand white New Zealanders. Aside from a completely different vocabulary for every day items and activities, the vowels are all shifted: a becomes e, e becomes i, i becomes a u of all things. Fish becomes 'fush', fashion is 'feshion', flesh becomes 'flish'. Despite being close to Australia (Ewan would deliberately draw out the aaaust, like someone here making fun of a Texan accent), New Zealand pronunciation is anything but: where vowels are drawn out into the down-under version of a southern drawl ('no' has like three different vowels in it and ends in an r, like 'naaur'), in NZ the vowels are short and clipped, meaning that innocent Americans are frequently going to look confused until a waiter will give a loud, and painfully drawn out American-ized pronunciation (this happened constantly for about the first month I was down there!). If you want some more exposure to the lovely and bizarre Kiwi accent, I encourage you to watch such films as What we Do in the Shadows, The Hunt for the Wilderpeople, or the show Flight of the Conchords.

A regional geologic map of Zealandia and surrounding trenches. For non-geologists, the lines with the black teeth on them are thrust faults/subduction zones, the teeth pointing towards the overriding slab. Note how the teeth change direction from along the Kermadec trench northeast of New Zealand (oceanic crust moving west and being subducted) versus the Puysegur trench (oceanic crust on west being subducted under east). This difference in direction is largely responsible for formation of the Alpine fault, which is *mostly* a strike-slip fault, and has resulted in shearing of New Zealand. From Schellart et al. (2006).

Major Geological Events in New Zealand

Today, Zealandia is located at the southern terminus of the Tonga-Kermadec Trenches* - a subduction zone formed where the Pacific Plate is being subducted below the eastern edge of the Australian Plate. This subduction zone transitions into a transform boundary - forming one of the largest strike-slip faults in the western Pacific: the Alpine Fault. This is sort of the southwestern Pacific equivalent of the San Andreas fault. For every four meters of lateral movement, there is an additional meter of uplift - resulting in the incredibly rugged Southern Alps on the South Island. I've been there, they are nothing short of magnificent - and if you've seen The Lord of the Rings, you'll certainly agree. Strike slip faults are of course not static - they move continental crust around horizontally - so New Zealand (the emergent, major landmass of Zealandia) has undergone quite a bit of change as it has been sheared over the course of the Cenozoic. Just as the rocks to the west of the Alpine Fault are part of the Australian Plate, the rocks to the east are part of the Pacific Plate. South of the South Island, the plate boundary goes back into the ocean, forming the Puysegur trench between the Australian and Pacific plates, which continues south (with some name changes) towards the Macquarie Triple Junction where a spreading ridge is producing more oceanic crust, resulting in the slow push of the Pacific Plate north and west, causing all of the subduction and also the slow movement of the parts of New Zealand east of the Alpine Fault north, scraping against the rest of the landmass to the west.

*There is a volcanic arc that runs northeast along the Kermadec and Tonga trenches, and this trench makes a left (westward) turn at Tonga/Fiji. Tonga marks the eastern-most volcanic arc in the south/tropical Pacific, defining a major geological boundary called the "Andesite Line". Andesite at minimum requires some continental-ish rock enriched with at least a little bit of silica to form - and andesitic volcanoes are on the bigger end of things, forming towering stratovolcanoes, also known as composite volcanoes, like Mt. St. Helens, Mt. Rainier, Crater Lake (formerly Mt. Mazama), Mt. Fuji, and Mt. Taranaki in NZ (Mt. Taranaki stood in for Mt. Fuji in "The Last Samurai" and Mt. Doom in Lord of the Rings). Stratovolcanoes tend to explode, and some of the most famous eruptions on earth - Krakatoa and Tambora - erupted west of the Andesite Line, in Indonesia. All volcanism east of the Andesite Line consists of intraplate volcanism only - volcanoes shooting up magma at hotspots, burning holes in oceanic crust, forming un-enriched heavy, iron/magnesium rich and super runny basaltic lava. East of the Andesite Line you get Hawaiian-style eruptions - eruptions you can walk, run, or drive away from. West of the Andesite Line? Explosive eruptions that might kill you by pyroclastic flow, steam explosions, tsunamis, or regional devastation that might alter the long term livability and economy of your island.

There are plenty of older rocks in the country, but the story of Zealandia really starts in the Cretaceous when it finally split apart from Australia - and no self-respecting Kiwi would want to dwell on a time period where Zealandia was simply part of Australia! Around 80 million years ago, continental rifting resulted in Zealandia breaking off the east coast of Australia and migrating eastward. A brief refresh: the famous supercontinent Pangea formed during the Carboniferous period some 300 million years ago, and began to rift apart around 200 million years ago around the Triassic-Jurassic boundary. By the late Jurassic, Pangea had rifted into two major landmasses separated by a narrow North Atlantic: Laurasia (North America, aka "Laurentia", and Europe/Asia), and Gondwana (South America, Africa, Madagascar, Antarctica, Australia, India, and Zealandia). By the early Cretaceous, the South Atlantic began to form, separating South America from Africa; Africa started drifting North, with Madagascar also separating from everyone else, and India began skittering northwards at a breakneck pace (and it would eventually collide with Asia around ~40 million years ago in the late Eocene, beginning the uplift of the Himalaya, which are of course still being uplifted today).

Continental geography of the south pole during the Paleocene and Eocene, prior to the final separation of Antarctica from South American and Australia and the resultant formation of the circum antarctic current. From Reguero et al. (2013).

What this resulted in was a big of a strange remnant of Gondwana: South America, Antarctica, Australia, and Zealandia (for a short while) remained connected in the "west" to the Antarctic Peninsula (which is in West Antarctica) and Australia to the north of East Antarctica, and Zealandia stuck on to the east coast of Australia. Zealandia separated first, and drifted at a leisurely pace (much, much, much slower than India), while Australia, and South America remained attached to Antarctica until the Eocene epoch. During the mid-late Eocene, each of these landmasses finally began to rift apart from Antarctica. It's uncertain which happened first, but what's very neat is that thanks to fossils from Seymour Island (same locality as Llanocetus, the oldest baleen whale), there were South American mammals inhabiting the Antarctic Peninsula well into the middle Eocene. Some of these fossils indicate that there were early Xenarthrans present - the group including modern armadillos, sloths, and anteaters - along with litopterns, an extinct group of placentals also unique to South America - and a host of different marsupials with South American links. Plant fossils indicate a temperate forest dominated by southern beech (Nothofagus), very similar to the native forest in New Zealand today. Given these fossils, it's likely that South America was still firmly attached - but the opening of the Drake Passage between Antarctica and South America is still unclear. The date of separation between Australia and Antarctica - the formation of the Tasmanian Seaway - is better understood, and seems to have opened to such a degree to permit deepwater circulation by 33.5 mya. This changed everything - locally, but also on a global scale - with permanent consequences for the earth since.

Geographic and climatic changes associated with the formation of the Circum Antarctic Current (aka circumpolar current) during the Eocene-Oligocene transition. From Nelson et al. (2004).

The final separation of these landmasses finally isolated Antarctica, resulting in the setup of the deep water Circum-Antarctic Current, sometimes called the circumpolar current, or the Antarctic Circumpolar Current (ACC). The ACC is the world's refrigerator: this west to east current prevents a southern hemisphere version of the gulf stream from delivering any warm, moist air - and seawater - to Antarctica. Antarctica, formerly a temperate forest teeming with life similar to its former neighbor continents, became rapidly glaciated at the Eocene-Oligocene boundary. With no possibility of interference of warm air and water, each winter became slightly cooler until it was cold enough to snow year-round, eventually forming the first continental ice sheets on the continent.* The famous La Meseta Formation on Seymour Island, where marine faunal change at the south pole during the Eocene has been best studied - terminated sedimentation, as sea level was lowered considerably below. In many places in the world, the Eocene marine record simply ends and rocks of late Eocene age are overlain by terrestrial rocks, or incised into by erosional surfaces (as nonmarine sedimentation on coastal plains is scattered and unreliable, often haphazardly causing widespread erosion and limited nonmarine deposition). At the famous Egyptian locality Wadi-Al-Hitan ("Valley of the Whales"), for example, the spectacularly fossiliferous marine sequence from which ~10 million years of incredible fossils chronicling whale evolution, ends with the deposition of the shallow marine to lagoonal Qasr el Sagha Formation of latest Eocene age, and is overlain by the nonmarine Oligocene Gebel Qatrani Formation - which produced some pretty famous land mammals like the early proboscideans Moeritherium and Phiomia and the double-horned embrithopod Arsinoitherium. While I would prefer some Oligocene cetaceans of course, maybe it's OK to have gotten some early afrothere 'weirdos' like these, I'd call that a solid tradeoff between marine/nonmarine fossils!

*This is the traditional model of Antarctic glaciation - however, there's some evidence of a smaller ice cap earlier, perhaps during the middle Eocene and even the late Paleocene has been suggested - and the glaciation has also been hypothesized to stem from a decrease in atmospheric CO2 - formerly in the thousands, it dipped below the 600 ppm tipping point, triggering a rapid transition from greenhouse to icehouse conditions. Within the last decade, we recently exceeded 400 ppm CO2, transitioning from a pre-industrial ~280 ppm.

In Europe the Eocene-Oligocene boundary marks an extinction event where many endemic mammals became extinct, and were replaced by invading mammalian species of Asian origin - this faunal difference has been called "Grande Coupure", or "the big break". Cooling during the Oligocene led to limited expansion of grasslands and more temperate forests, and a bit of a reduction in tropical rainforest/jungle habitat that was so common during the Eocene.

Geographic and tectonic evolution of New Zealand, with modern shorelines superimposed. It used to look quite a bit different, and is only elongated into the two islands now because of shearing along the Alpine fault. From Reilly et al. (2015).

In New Zealand, there isn't as much of a stark difference because most of Zealandia remained underwater. middle-late Eocene rocks are plentiful, though sparsely fossiliferous and with sparse outcrops. Terrestrial pollen from NZ shows a transition from warm, humid forests to more temperate forests during this time, but as far as marine rocks are concerned, little much of a difference. In fact, around the Eocene-Oligocene boundary, the sequence is interrupted along the Otago coast by volcanic rocks. The Ototara Limestone - a thick, monotonous tan to white limestone mostly composed of bryozoan fragments* - preserves the Eocene-Oligocene Boundary, marked by the extinction of the foraminifer ("plankton") Hantkenina.

*Also known commercially as Oamaru-stone or Totora-stone, virtually all pre-WW1 buildings in the town of Oamaru are carved from this limestone, making it quite bright/reflective on a rare sunny day, and also a popular source of stone for local sculptors. I still regret not purchasing a Muri Paraoa (whale flukes) I saw for sale at a farmer's market in Dunedin, but it would have come at the cost of a week's groceries and any heat we would have needed.

Highly burrowed unconformities in the middle Oligocene of New Zealand, with the Oligo-Miocene Kokoamu Greensand, Otekaike Limestone and Gee Greensand overlying the Ototara Limestone (early Oligocene). From Thompson et al. (2014).

The first noticeable perturbation in the marine record of NZ is a widespread erosional surface, called by earlier stratigraphers as the "Marshall Paraconformity". An unconformity is an erosional surface, and a paraconformity is one such type - it's basically similar to a disconformity, where there is a difficult-to-identify erosional surface present between rock layers above and below that are parallel in bedding, differing from an angular unconformity where the rocks below have been tilted. The "Marshall Paraconformity" itself has been a locally controversial topic amongst NZ stratigraphers (summarized here by Mike Pole) and in reality might be two or more different unconformities, which seem to have erased 2-3 million years of the marine record in parts of NZ. In the whale-bearing rocks of the south Canterbury Basin, the top of the Ototara Limestone is heavily bored/bio-eroded and even shows evidence of karst dissolution. It has been overlain by the Kokoamu Greensand. Further inland, the Ototara Limestone transitions into the deeper marine Earthquakes Marl, and further inland yet, the Wharekuri Greensand - also overlain by the Kokoamu Greensand. The cause of this erosion is unclear, but may have been driven by some "glacioeustatic" fluctuations in sea level - brief expansions of the Antarctic Ice sheet that temporarily lowered sea level during the middle Oligocene.

Maps of likely emergent land from the Oligocene onward, modified from work by Charles Fleming. From https://slideplayer.com/slide/16841854/.

The last relevant geological event may or may not have happened - but during the Oligocene there was a period of rather high sea level - that may, or may not, have completely submerged Zealandia. This debate was raging just as I got to New Zealand. During the Oligocene, there are basically no terrestrial sediments, and all known Oligocene aged marine rocks are marine. Many geologists argued that this indicated the entire landmass was completely underwater for at least a few million years - highlighting many lineages of terrestrial organisms that seem to have been post-Oligocene arrivals, and the complete absence of native terrestrial mammals, aside from bats, which almost certainly flew across the Tasman sea. However, plenty of scientists - Fordyce included - fervently disagreed, pointing out that there's no shortage of lineages that either 1) are endemic today and have molecular divergence dates from other endemic species pre-dating the Oligocene and 2) some animals like the Tuatara, Sphenodon punctatus - a strange lizard-like reptile that is today unique to New Zealand. This group, the Rynchocephalia, were formerly globally distributed during the Mesozoic (and were quite diverse here in North America during the Triassic), but declined during the early Cretaceous, restricted to what remained of Gondwana (South America, Antarctica, Australia, Zealandia) after becoming extinct in North America, Europe, Asia, and Africa during the early and late Cretaceous. Though no pre-submergance Tuatara are known from NZ, their last occurrence outside Zealandia is from the earliest Paleocene of Patagonia, strongly suggesting that they've been endemic to Zealandia since the Paleocene.

Ewan Fordyce teamed up with Ken Rose, Hans Dieter-Sues, Carolina Loch, and Mike Gottfried for a project called "The Lost Mammals of Zealandia", a search for Paleogene fossil land mammals in shallow marine sediments where he had found some evidence that terrestrial fossils might be found. As of 2014, no precious mammal teeth had been discovered during the pilot project, but a single crocodylian tooth had been recovered - the oldest from the continent. The hope was, if any land mammal teeth were found, they would be readily identifiable and with likely biogeographic signal (e.g., these teeth clearly resemble species from Australia, which, all nationalistic joking aside, is the most predictable affinity for any Paleogene Zealandian mammals). The search continues.

The New Zealand Geological Time Scale and mid-Cenozoic Stages

In a characteristic display of independence, New Zealand proudly boasts its own Geologic Time Scale. I had some knowledge of this prior to my arrival in 2012, but had a bit of a baptism by fire my first few months. New Zealand is so isolated, that many of the correlations of marine rocks in Zealandia require careful comparisons between other NZ localities, rather than Australia or further afield - necessitating to a degree its own time scale. Australia has its own time scale, for similar reasons, though it is less widely used than the international scale.* These are chronostratigraphic units, relating physical rock layers to specific periods of time. Most chronostratigraphic units are based on a reference section somewhere on earth. In the case of the Duntroonian Stage - one that we're going to talk about the most in this series, I think - is based on exposures of the Oligocene Otekaike Limestone in the vicinity of Duntroon, New Zealand. More on Duntroon later.

*Along the west coast of North America, we have several timescales for each type of microfossil - the diatom zones, initially divided into stages with roman numerals, and benthic foraminiferal stages like the Eocene-Oligocene Narizian, Refugian, and Zemorrian stages - sadly, best a cudgel-like biostratigraphic tool rather than a scalpel. In the past two decades Pacific coast stratigraphers have more completely adopted the international stages defined by the ICS, largely defined on European localities.

The New Zealand geologic time scale: from Raine et al. (2012).

For the period of time concerning fossil whales, we're really focused on the Bortonian, Kaiatan, Runangan, Whaingaroan, Duntroonian, and Waitakian stages. The Bortonian through Runangan are Eocene in age, with the Bortonian confusingly being broadly equivalent to the Bartonian middle Eocene stage; the Kaiatan and Runangan are generally late Eocene in age, roughly equivalent with the international Priabonian stage. These three stages comprise the Arnold Series - named after strata exposed along the Arnold River in the West Coast district of the South Island. Likewise, the Runangan is

The next three are roughly coincident with the Oligocene, but actually include the last million years of the Eocene and the first two million years of the Miocene. The Whaingaroan stage is broadly equivalent to the Rupelian of international usage (early Oligocene), while the Duntroonian represents the early Chattian (late Oligocene), and the Waitakian stage represents the latest Oligocene and first million years or so of the Miocene. These three stages make up the Landon Series, named after Landon Creek, between Oamaru and the mouth of the Waitaki River. The Whaingaroan is named after strata in the vicinity of Whaingaroa, south of Auckland on the North Island, whereas the Duntroonian derives its name from the hamlet of Duntroon along the Waitaki River in South Canterbury - which also happens to give its name to the following Waitakian stage.

Generalized stratigraphy of the southern Canterbury Basin (occasionally called the Waitaki Basin by some authors, but not Otago geologists). From Thompson et al. (2014).

A Brief Introduction to mid-Cenozoic Stratigraphy of the Canterbury Basin

Deposition of the Canterbury Basin starts in the Cretaceous, and the late Cretaceous Katiki Formation has produced spectacular fossils like Kaiwhekea - the "shag point" plesiosaur*, and a sparsely fossiliferous sequence from the Paleocene and early Eocene.

*'Shag' is an archaic English name for cormorants. Fordyce always called this specimen "Shagosaurus" to get some laughs.

Some panoramic shots of some of the more important Oligocene paleocetological localities in North Otago and South Canterbury. The holotypes of Waipatia, Aureia, Horopeta, Waharoa, Tokarahia, Tohoraata, Whakakai, Toipahautea, Kairuku, and Plotornis archaeonautes (and more) all came from within these photos or slightly out of frame. Photos by me, 2012-2014.

Waihao Greensand: The Waihao Greensand is middle to late Eocene in age, and best exposed in the vicinity of Waihao in south Canterbury. This unit is a massively bedded glauconitic sandstone, frequently a grayish green color. Invertebrates are rare but include a fossil lobster. Many bony fishes are reported form otoliths. The leatherback sea turtle Psephophorus terrypratchetti was reported, along with specimens of Zygorhiza (see below), are the best known vertebrates from the Waihao Greensand.

Ototara Limestone: One of the more important sedimentary units, historically used as a source of building stone; most of the older buildings in the coastal town of Oamaru are built out of this material, colloquially called "Oamaru Stone" (some of the parts of the Geology and Registry buildings at Otago are made of this material as well). It's also used for stone carvings, quite common on the South Island. The Ototara Limestone is dominated by bryozoan fragments, giving it a medium to coarse sandy texture. It's frequently massively bedded, and in the vicinity of Kakanui, interfingers with lavas from small marine cinder cones. The Ototara Limestone is Eocene through early Oligocene in age. The very first fossil penguins ever reported were discovered in the Ototara Limestone in the 1840s - indeed, Palaeudyptes antarcticus was named in 1847 by none other than Darwin's bulldog, Thomas Huxley. Later, the titanic penguin Pachydyptes was also named from the Ototara. The only cetacean to be reported from this unit is the "Protosqualodont" of Keyes (1973).

Amuri Limestone: This unit is a lateral equivalent of the Ototara Limestone, and exposed in North Canterbury. It is a chalky unit consisting mostly of coccoliths and foraminifera deposited in outer shelf to slope settings. So far only one fossil cetacean is known from this unit, ZMT 62.

Earthquakes Marl: This unit is poorly exposed and has not produced much in the way of significant vertebrates, but is a lateral equivalent of the Ototara Limestone, typically exposed further inland. It is the lowermost unit exposed at "The Earthquakes" and Waipati. It consists of gray calcareous siltstones

Kokoamu Greensand: This unit is a sandy, invertebrate rich outer shelf deposit consisting of pervasively burrowed, massively bedded glauconitic sandstone. It is considerably more friable and tends to weather away rapidly at the base of cliffs, and natural exposures typically include only the uppermost couple of meters below the Otekaike Limestone. The Kokoamu is uppermost Whaingaroan in age to upper Duntroonian (~28-26 Ma). Common fossil invertebrates include brachiopods and scallops, especially at the top of the unit, where it becomes more calcareous - leading to a gradational contact with the overlying Otekaike Limestone. Fossil sharks, penguins, and cetaceans are common; fossil cetaceans include Mammalodon hakataramea, Kekenodon onamata, Tohoraonepu nihokaiwaiu, Tokarahia lophocephalus, Tohoraata waitakiensis, Matapanui waihao, and Toipahautea waitaki. Two species of dolphins have been named from the Kokoamu, both waipatiids - Awamokoa tokarahi as well as Nihohae matakoi, though there is an unnamed squalodontid as well; doubtless there are others. Penguins include the giants Kairuku waitaki and Kairuku grebneffi, and the earlier named Archaeospheniscus lowei, and Platydyptes marplesi. The Wharekuri Greensand and "Kekenodon beds" are lateral equivalents of the Kokoamu Greensand.

Otekaike Limestone: This unit overlies the Kokoamu Greensand and the two units constitute a depositional package. The Oteikaike Limestone is glauconitic at the base and grades up into a sandy, foraminiferal limestone, representing middle shelf deposition and preserves abundant invertebrates - most common are bivalves, bryozoans, brachiopods, gastropods, and tube worms, but crinoids, basket stars, and cold water corals (including octocorals) are also present. The Otekaike Limestone is massively bedded and a ridge former, and many spectacular cliffs are developed in North Otago and South Canterbury; some of these cliffs even appeared in the first Hobbit movie (though possibly could have been the Weka Pass Limestone). It dates to the late Oligocene, being about 26-22 million years old, or Duntroonian through Waitakian. Locally it is an important source of agricultural lime, and Hakataramea Quarry is a critical source of such lime. The Weka Pass Limestone in North Canterbury is a northern equivalent of this unit (the cliffs in the final battle in The Lion, the Witch, and the Wardrobe were filmed at a famous Weka Pass Limestone exposure) - though it is nowhere near as rich in fossil vertebrates. This unit is easily the most heavily studied in New Zealand. Many fossil fish and sharks, including the giant shark Carcharocles angustidens, the giant moonfish Megalampris keyesi, and the billfish Aglyptorhynchus hakataramea are all known from the Otekaike Limestone (though far down in the lower, glauconitic limestone in the case of the former two). Penguins include Platydyptes and the recently named dwarf penguin Pakudyptes. Fossil cetaceans are common and include a kekenodontid archaeocete (new genus and species), waipatiid dolphins (Waipatia maerewhenua, Waipatia hectori, Nihoroa reimaea, Aureia rerehua, Otekaikea marplesi, Otekaikea huata), at least one squalodontid (the Earthquakes squalodontid), eomysticetids (Tokarahia kauaeroa, Tohoraata raekohao, Waharoa ruwhenua), "Tsai's whales" (Whakakai waipata, Toipahautea waitaki, Horopeta umarere), Mauicetus and friends (Mauicetus parki, and ZMT 67). There are other "interesting" (to put it extremely mildly) cetaceans I can't talk about, but at least one has been reported in a conference abstract: a mysticete with an arched rostrum, OU 22224, which Ewan originally considered to be an Oligocene balaenoid (right whale), but at present, might instead be something more archaic (see part 2).

Gee Greensand: The Gee Greensand is a thin, friable glauconitic sandstone of early Miocene (Otaian stage, ~19-21 Ma) age and is mostly exposed close to the coast, such as in the vicinity of Kakanui (and poorly exposed at that). The Gee Greensand has produced a single fossil cetacean, Tangaroasaurus kakanuiensis.

Mt. Harris Formation: The Mt. Harris Formation conformably overlies the Otekaike Limestone and consists of somewhat deeper marine siltstone; in the vicinity of Awamoa Beach, numerous light gray siltstone concretions have been collected that contain cetacean bones. Few fossil cetaceans have been reported from this unit, other than a partial skull of Prosqualodon. Many others are sure to follow. The Mt. Harris Formation is Otaian to Altonian, roughly 21-18 Ma in age.

Caversham Sandstone: The Caversham Sandstone is a lateral equivalent of the Mt. Harris Formation, and is a thick, massively bedded yellow sandstone that forms the spectacular coastal cliffs southwest of Dunedin as well as further north of the Otago Peninsula from Karitane nearly to Shag Point. Only one fossil odontocete has been formally named from this unit, "Prosqualodon" hamiltoni, a large Phoberodon-like beast (see part 3); several smaller dolphins, including kentriodontids, were studied by Gabriel Aguirre-Fernandez as part of his Ph.D. thesis and await formal publication. The Caversham Sandstone is Otaian to Altonian in age (21-17.5 Ma).

The southeast cliff at Hakataramea Quarry, aka Haugh's Quarry - this was the original natural exposure, quarrying is to the left. The holotypes of Toipahautea and Horopeta were collected between where I was standing and where Ewan (red shirt) is, and the large hole he's examining is where the unnamed "Chocolate whale" was excavated. The grass-filled hole in the quarry at the upper left is where the paratype skull of Waharoa was collected. The olive green layer at the base of the cliff is the top of the 'mid' Oligocene Kokoamu Greensand, and the rest is all upper Oligocene Otekaike Limestone. Photo by me, 2013.

Tunnel Beach, South Otago, New Zealand - these impressive cliffs are exposures of the somewhat younger Caversham Sandstone (early Micoene). No mysticetes (or archaeocetes) from this unit, but I'll cover some of the odontocetes from this unit in part three. Photo by me, 2013.

The Fossil Record of Archaeocete Whales in New Zealand: Basilosauridae

Archaeocete whales - the ancestors of baleen whales and toothed whales - are predominantly known from the Eocene epoch, and document how hoofed mammals began experimenting with a semiaquatic existence, rapidly changing from an herbivory to carnivory, and the slow transition from a running mammal to one that swam, first quadrupedally, and then eventually with flukes and flippers. The earliest groups of archaeocetes, the semiaquatic raoellids, pakicetids, ambulocetids, are known only from India and Pakistan. The remingtonocetids were the first to be found preserved in marine strata, and have been found slightly further afield in Egypt (Rayanistes) and possibly eastern North America. The protocetids, the last group to have any ability to support their weight on land - have now been found in Indo-Pakistan, Egypt, Morocco, Europe, Togo, the southeastern USA, and most recently, Peru. The last group, the Basilosauridae, have a near-worldwide distribution - most famously they are known from Egypt and the southeastern USA, but there have been a number of amazing discoveries in Peru, such as well-preserved Cynthiacetus peruvianus and the titanic whale Perucetus colossus, and many additional as-yet undescribed species and specimens from the "valley of the archaeocetes".

The very first archaeocete fossils (1-5) collected form New Zealand in the late 19th century - identified as Dorudon by Fordyce (1985). From Fordyce (1985).

This latter group is the only classical group of Eocene archaeocetes known from New Zealand. The first known specimen was a collection of three associated teeth from the Waihao Greensand of South Canterbury, described by Ewan Fordyce (1985). This specimen has a bit of an interesting post-collection history. One of these teeth, a single premolar similar to Saghacetus osiris, was present in the collections of the NMNZ collections at what is now Te Papa Tongarawea - the NZ national museum in Wellington (I'll just call it Te Papa if it comes up again), and mixed in with the type specimen of the problematic early whale Kekenodon onamata (keep reading), but morphologically and having some preservational differences. Fordyce noticed this in 1975 and concluded it was from a different specimen, but it bore no markings or associated notes to indicate exactly where it was from. Two years later, while visiting the Canterbury Museum in Christchurch (the other big city on the South Island other than Dunedin, and where Ewan did his Ph.D. research), he found a specimen consisting of a canine-like tooth and a fragment of a root, bearing the identification of "Crocodile Waihao". These other two specimens were preservationally similar to the mystery tooth found at Te Papa, but also share similar enamel thickness and surface tecture, along with similar rock attached - which happened to be similar looking greensand. What really clinched the identification was the fact that the three tooth fragments have identical glue attached to them, and were at one point affixed to a sheet of card and evidently put on display, and sunlight damaged the card but left little shadows showing the outlines of the teeth - and there was an outline matching the premolar found at Te Papa. The specimen was united and assigned a new specimen number at Canterbury Museum after this detective work. It is thought to have been collected very, very early - perhaps by the early geologist-explorer Julius von Haast, and Fordyce speculated that the premolar may have been taken to Te Papa in the 1880s during James Hector's study of what he later named Kekenodon onamata - the specimen was not figured or considered part of the type specimen by Hector. Fordyce concluded that these teeth are assignable to some sort of "dorudontine"* basilosaurid, and made comparisons with Saghacetus osiris from the uppermost Eocene of Egypt, and indicated that the tooth is a bit smaller than Zygorhiza from the USA. Critically, Fordyce also summarized other fragmentary records that had been assigned from the Oligocene of Australia and New Zealand and concluded that most of these other specimens represent archaic toothed mysticetes and odontocetes - the New Zealand specimens of which I'll review in this same series. As a result of this revision, Fordyce (1985) pointed out that this was the first definitive record of an archaeocete as well as the oldest known cetacean from NZ.

*The taxonomy of the Basilosauridae has been revised several times - most notably by Kellogg (1936), but later by Barnes and Mitchell (1978), who left lasting definitions of the "Dorudontinae" and "Basilosaurinae" - two subfamily names, placed here tactically in scare quotes - which have in recent years become less-than-useful ideas. Essentially, the Basilosaurinae was used to contain Basilosaurus cetoides and Prozeuglodon isis, gigantic species with elongated thoracic and lumbar vertebrae. However, P. isis was later reassigned to Basilosaurus and recombined as Basilosaurus isis, essentially making gigantic size and elongated vertebrae unique to the genus Basilosaurus - and making the subfamily not needed, because the "Dorudontinae" ended up including all other basilosaurids. With Perucetus, Cynthiacetus, Tutcetus, and the Basilotritus-Platyosphys-Pachycetus-Aithacetus quagmire, the situation has changed somewhat, and pending phylogenetic analysis of the family, perhaps some subfamilies may still be useful, but not until then.

The first truly significant archaeocete fossil from New Zealand, a well-preserved braincase with periotic and associated teeth from the Bortonian Waihao Greensand of south Canterbury, identified as Zygorhiza. From Kohler and Fordyce (1997).

Closeup of the periotic and tooth of the Waihao Greensand Zygorhiza, from Kohler and Fordyce (1997).

Further Eocene archaeocete material would not be discovered until 1991, when collector P.A. Maxwell found a partial basilosaurid skull, and further field trips from 1992-1995 recovered a few additional specimens including teeth and some vertebrae. Owing to the rarity of specimens in the Waihao Greensand, and their close association, these specimens - though assigned different numbers - were considered to be one specimen. These specimens formed part of the basis for Richard Kohler's PhD thesis at Otago, and were formally published by Kohler and Fordyce (1997). These specimens were assigned to Zygorhiza, previously known only from the uppermost Eocene Yazoo Clay and equivalent units on the gulf coast of the USA - chiefly Louisiana, Mississippi, and Alabama. Zygorhiza has been differentiated from other basilosaurids only based on one major dental feature: having a well-developed ridge or cingulum at the base of the cheek teeth, absent in other basilosaurids. An additional dental feature seems to define Zygorhiza: a thick posterior root on the premolars, a vestige of the two posterior roots in earlier archaeocetes and land mammals that fused together. One other key feature is possessing a slightly "telescoped" skull - with the occipital shield, the bone that makes up the back of the braincase - shifted further like as is seen in early mysticetes and odontocetes, and a nuchal crest that forms a slight shelf. In other basilosaurids, it is instead vertical. Uhen (2013) found the top of the skull to be quite variable in Zygorhiza. Regardless, the Waihao basilosaurid possesses all three of these features, and was identified as Zygorhiza sp. by Kohler and Fordyce (1997).

More recently, a neonatal or perinatal archaeocete skeleton was discovered in the upper Eocene Ashley Mudstone of Canterbury and reported by Fordyce and Hiller (2014) in an SVP conference abstract. I saw the specimen in person during my Ph.D. - it is tiny - but has adult-sized periotics, and a skull measuring only about 30 cm, with a number of milk teeth. The specimen has not yet been published.

The holotype fragments of Kekenodon onamata from the "Kekenodon beds" (=Kokoamu Greensand), from Hector (1881).

The Fossil Record of Archaeocete Whales in New Zealand: Kekenodontidae

In November 1880, a fragmentary archaeocete-like whale was discovered by Alexander McKay in the vicinity of Wharekuri Creek in the Waitaki Valley, from an Oligocene aged unit later called the Kekenodon beds, and later correlated with the Kokoamu Greensand. The specimen consists of a set of rather large teeth including incisors, a canine, premolars, and molars, along with the right frontal bone, a periotic, and a bulla. It seems likely to me, and when I suggested this, Ewan seemed to agree - that the original specimen as found in the field likely had rather crumbly, fragmentary bone that did not survive primitive collecting methods. As a result, only relatively durable parts remain. This specimen was named Kekenodon onamata by James Hector in 1881, who thought it may be similar to archaeocetes like Basilosaurus, but also compared it with modern seals; Hector ultimately named it Kekenodon, meaning seal tooth in combined Maori and Greek. Kellogg considered Kekenodon to likely represent a basilosaurid in his 1936 monograph, and Mitchell (1989) generally agreed, but noted the teeth were quite distinct and would necessarily represent a highly derived "dorudontine" - the cheek teeth trend towards having single roots with a trilobate cross-section rather than widely divided double roots, lack a cingulum on the lingual side of the enamel crown, generally more complex surface texture on the cheek tooth roots, and lower molars that have mesial cusps and critically lack this vertical groove called the 'reentrant groove'.

The holotype right frontal bone of Kekenodon onamata - the only non-earbone part of the skull that was preserved. From Corrie and Fordyce (2022).

The holotype periotic of Kekenodon onamata. From Corrie and Fordyce (2022).

The holotype tympanic bulla of Kekenodon onamata. From Corrie and Fordyce (2022).

As early as 2004, Ewan Fordyce considered kekenodontids to be archaeocetes that were very close to Neoceti, and called them "transitional Neoceti". This is quite significant, as prevailing wisdom held that the basilosaurids, specifically the dorudontines if you believed Barnes and Mitchell - were the immediate ancestors of Neoceti. This was informed partially by the holotype of Kekenodon, but also greatly influenced by a suite of new fossils from the Kokoamu Greensand and basal Otekaike Limestone found by Fordyce and his earlier students and museum staff, chiefly in the 1990s (I'll discuss these below). In 2022, Josh Corrie and Ewan Fordyce published the first chapter of Josh's PhD thesis, reevaluating the type specimen of Kekenodon onamata. Though belonging to Te Papa Tongarewa National Museum of New Zealand, the specimen had been on loan to Fordyce for years - all of the really significant whale remains under one roof. I examined the teeth and earbones of the specimen several times during my Ph.D.

The holotype teeth of Kekenodon onamata - top image shows the anterior incisors/canines, and the bottom image shows the premolars and molars. From Corrie and Fordyce (2022).

The above-mentioned differences in tooth shape are rather trivial when compared to most toothed mysticetes, however: the teeth are rather enormous and generally basilosaurid-like in most respects, with a similar pattern of heterodonty - amongst toothed mysticetes, premolars and molars look nearly alike, but within basilosaurids, each tooth position can be picked apart and this is true of Kekenodon: each premolar position is obvious, as are the molars. Slight differences by position in toothed mysticetes are further smeared by having an increase in tooth count (polydonty). As for tooth size, the only toothed mysticetes with similarly enormous teeth are Coronodon (not known until the 1990s), Llanocetus, and Mystacodon (not known until the late 2000s).

The spectacular skull of OU 22294 - an unnamed genus and species of kekenodontid currently under study by my former labmate Josh Corrie. He's in the final stages of getting this beast named. This is the only published image of the specimen, so I'll stick to features that are clear from the image: it obviously has an un-telescoped skull and is most similar to small basilosaurids like Zygorhiza, but the occipital shield is positioned much further anteriorly, the bony naris further posteriorly, it lacks a sagittal crest, and has an open mesorostral groove - all features linking it more closely with the Neoceti. From Clementz et al. (2014).

The most spectacular specimen, however, is OU 22294 - a nearly complete skull that in outline and general morphology looks quite a bit like a small basilosaurid, but does have a bunch of features shared with toothed mysticetes like Coronodon and especially Mystacodon. The specimen is still under study by my Otago labmate and colleague Josh Corrie, so I will refrain from remarking on anything about this specimen that isn't already in the literature somehow, or what is clear from published images (e.g. Clementz et al., 2014, above). Ewan told us during our program that when they first came upon the specimen in the field, sticking out of an overhang in a cliff, he suspected it was a squalodontid. However, during the initial excavation, a fracture developed in the rostrum, revealing that the mesorostral groove was roofed over - indicating that it was some sort of archaeocete. In early mysticetes and all odontocetes, there is a continuous groove present along the rostrum - the left and right premaxillae never really contact. In the early dolphin Xenorophus, the groove is narrow but the bones do not contact; a similar situation is present in Mystacodon. In Coronodon havensteini, the premaxillae contact at the tip but only for a few centimeters; aetiocetids are similar. In virtually all Oligocene dolphins diverging after xenorophids, the mesorostral groove is quite wide and continuously separated - then this groove is variably narrowed in modern odontocetes, and occasionally secondarily closed. The bony nares are also positioned further posteriorly - along the middle third of the snout rather than the anterior third - unlike basilosaurids. The braincase of this specimen is quite interesting as it has a Neocete-like degree of telescoping, with the vertex thrust forward; the skull is also quite low in height, much like a mysticete, with a broad occipital shield. The periotic is critically amastoid - in other words, the posterior process - also called the mastoid process - is shortened and not exposed on the lateral skull wall. There are some other fascinating features I'd love to discuss, but will wait until Josh's paper is published (and, will necessarily devote an article or two on this blog to the strange kekenodontids).

The holotype skull fragments of Tohoraonepu nihokaiwaiu, including the right frontal, right squamosal with articulated periotic, and the right tympanic bulla. From Corrie and Fordyce (2024).

The holotype teeth of Tohoraonepu nihokaiwaiu. From Corrie and Fordyce (2024).

Somewhat more recently, Josh published a paper in the Journal of the Royal Society of New Zealand naming a new fragmentary kekenodontid, Tohoraonepu nihokaiwaiu, from the Kokoamu Greensand (Corrie and Fordyce, 2024). Tohoraonepu translates to "sand whale", referring to the occurrence of this whale in greensand; nihokaiwaiu translates to "baby teeth". This specimen consists of an associated dentition and partial braincase with bulla and periotic, cervical, thoracic, and lumbar vertebrae, scapulae, partial humerus, radius, and ulna. The specimen is a juvenile, but also clearly much smaller than Kekenodon onamata as the teeth are quite smaller - suggesting a skull and body length (at least at death) that was about half (skull size) to one third the size (estimated body length). The teeth are the most interesting parts of the specimen - they are all developmentally young, and though they have hollow pulp cavities not yet filled, and an apparently diphyodont dentition in general: there are a mix of deciduous (milk) teeth with permanent molars, recording the only known occurrence of diphyodonty in a post-Eocene cetacean. The teeth are much more basilosaurid-like than in Kekenodon onamata, with widely separated root lobes, but have similar molars with mesial cusps that also lack the 'reentrant groove' to accommodate the upper molars. The enamel is extremely smooth - there are no apparent ridges or bumps, aside from a few subtle striations along the caniniform teeth and a few along the lingual (tongue side) of the cheek teeth), and also completely lack cingulum. There's no remnant of a third root, like Kekenodon. The teeth actually quite closely resemble Coronodon in many regards, but differ in having lower crowns and shorter roots (and their smaller size). The bulla looks very similar to aetiocetids, squalodontids, and eomysticetids, and more closely resembles these than basilosaurid bullae (or even the admittedly archaeocete-like bulla of Llanocetus, for that matter). The periotic is amastoid, and generally more similar to Coronodon than to any basilosaurid, especially in lacking a tall superior process.

Two southerners: Ewan Fordyce (left) speaking with his old friend and colleague Al Sanders (right), while examining what would become the holotype specimen of Coronodon havensteini five years later. Photo taken by me, 2012.

One last word on kekenodontids - I had seen some line drawings of the "Charleston toothed mysticetes" (now the family Coronodonidae), but unlike most other visitors to the Charleston Museum who examined these and never inspected a kekenodontid, I saw these specimens in 2012 after having seen Kekenodon onamata and other kekenodontids from New Zealand earlier in the year when I started my Ph.D. When I saw the periotic of the juvenile specimen of Coronodon havensteini, ChM PV 4745, and the specimen that would five years later become the holotype of the same species (CCNHM 108) - I immediately noticed how similar in morphology they were. From that point on I began wondering if the "Charleston toothed mysticetes" were North Atlantic kekenodontids.

The Fossil Record of Toothed Mysticetes in New Zealand

A handful of notable specimens that are clearly identifiable as toothed mysticetes have been collected from New Zealand. They are not quite as spectacular as some of the toothless mysticetes or the kekenodontids, but hold some promise of further, future discoveries and hint at some pretty neat looking critters. I'll note that, prior to Josh Corrie's thesis, Ewan considered certain specimens now recognized as kekenodontids to be possible toothed mysticetes - like the holotype of Tohoranepu. However, that changed once Josh started working on these specimens and finding more similarities with Kekenodon, and sure enough - they form a tightly supported clade in all of his phylogenetic analyses.

The teeth of OU GS 10897, the "protosqualodont" of Keyes (1973). This enigmatic specimen, likely to be a llanocetid, also includes a partial skull that is still under study by Felix Marx and the late Ewan Fordyce. This image is from Keyes (1973).

The earliest published specimen is the "protosqualodont" of Keyes (1973), otherwise known only as OU GS10897. This specimen consists of a couple of teeth reported by Keyes - and these teeth are seriously unique amongst cetaceans. They are robust, rather large teeth and relatively low-crowned, with radially oriented, stout accessory cusps with rugose enamel resembling Llanocetus denticrenatus. The premolar possesses one very archaeocete-like feature - there is a large 'protocone shelf' and a bulge on the posterolingual part of the tooth - and the posterior tooth root is thick, with a vertical groove - greatly resembling protocetid whale teeth, perhaps to a degree more than many basilosaurids. Though Keyes reported only on two teeth from the specimen, there was a partial skull embedded in a slab of limestone that was cut from Gay's Limestone Quarry - a quarry in the lower Oligocene Ototara Limestone, aka the famous 'Oamaru stone'. The specimen has an interesting post-collection history, and if memory serves, the quarry manager had the limestone slab tipped up against the wall years after Keyes reported on the teeth, and Ewan convinced the manager to donate the specimen. I won't comment on the skull anatomy, other than to mention it is similar to Llanocetus - and typically plots out in Felix Marx's various phylogenetic analyses as the sister taxon to Llanocetus. Predictably for the time, like many of these problematic strange teeth from the Oligocene, Keyes identified the specimen as some sort of squalodontid.

The holotype tooth of "Squalodon" serratus from the Weka Pass Stone of Canterbury, New Zealand - this specimen is likely to be something like Janjucetus from Australia. from Glaessner (1972).

The second is "Squalodon" serratus, which is an isolated tooth reported from North Canterbury by Davis (1888). This tooth has cusps like a basilosaurid, but is rather small, and narrow, rather than being a large, serrated triangle. The specimen was collected from the Weka Pass Stone of Canterbury, which is a lateral equivalent of the Otekaike Limestone. Glaessner (1972) reassigned the specimen to Squalodon - something later works by Fordyce disputed. Fordyce and Marx (2016) considered the specimen to possibly represent a southern hemisphere aetiocetid, though Ewan privately told me in 2013 or 2014 that it was likely to be from a mammalodontid, being particularly similar to Janjucetus - and I'm quite inclined to agree.

The jaw fragment of ZMT 62 - a possible small bodied llanocetid from the Whaingaroan (early Oligocene) Amuri Limestone. This specimen is not very big, slightly smaller than Zygorhiza. From Fordyce (1989).

The third is an unnamed specimen, ZMT 62 - an isolated mandible fragment with some partial teeth from the Amuri Limestone of North Canterbury. This fragment has a relatively shallow mandible with a nearly circular cross-section, clearly differentiating it from basilosaurids with deeper, oval cross-sections - however, the teeth are quite large, relatively and absolutely. Fordyce (1989) described this specimen and made comparisons with archaeocetes as well as Oligocene odontocetes and toothed mysticetes, concluding that the specimen most likely represented a toothed mysticete of some sort. In our 2017 paper on Coronodon, we actually coded the specimen into our analysis, and into our 2023 matrix for the Coronodon monograph, and in each case this specimen has formed a sister-taxon relationship with Llanocetus denticrenatus. The teeth are large and do have elongate cusps, similar apicobasal striations, and in all likelihood, a high number of accessory cusps. The specimen is likely to be a llanocetid, but further specimens are needed. Though of similar age and affinities, the specimen is almost certainly a different llanocetid than the "protosqualodont" of Keyes, outlined above - suggesting that the early Oligocene of New Zealand likely had two different llanocetids.

The holotype braincase, tooth fragments, and tympanic bulla of Mammalodon hakataramea, with the skull (H on left side) and tympanic bulla (G-K on right side) of Mammalodon colliveri from Australia for comparison.

The fourth and last example is actually named, like "Squalodon" serratus, but is also reasonably complete so as to be diagnosable - like the unnamed "protosqualodont". This specimen consists of the 'vertex' part of a braincase associated with a complete tympanic bulla and some partial teeth - collected by Ewan Fordyce and his field assistant/student Craig Jones and preparator Andrew Grebneff in 1987 from a stream exposure of the Kokoamu Greensand in Sisters Creek, nearby the unusually productive "Haugh's Quarry" in Hakataramea Valley in south Canterbury (many more finds from Haugh's Quarry to be covered in the next two posts). Felix Marx and Ewan Fordyce published this specimen in 2016 and named it Mammalodon hakataramea. Though fairly incomplete, the specimen is quite clearly referable to Mammalodon, with a similarly shaped cranial vertex but that is somewhat narrower and subtriangular. Along with some subtle differences in the shape of the tympanic bulla, M. hakataramea also has teeth that are worn down to the gumline - the teeth being reduced to roots. Along with specimens like "Squalodon" serratus, Mammalodon hakataramea indicates that mammalodontids inhabited the continental shelves of Zealandia along with Australia. Thus far, mammalodontids have not been reported outside these regions (aside from a partial dentition from the lowermost Miocene of Malta), and I hope at some point we might hear of similar finds made from the Oligocene of South America or even the North Pacific.

A partial tooth of Llanocetus sp. from the Chatham Islands. From Marx and Campbell (2025).

Most recently, Felix Marx and Hamish Campbell have published a short article on a fragmentary tooth from the Chatham Islands that superficially resembles a basilosaurid tooth - collected by Bob Weston, but from an unknown locality. The Chatham Islands are about 800 km east of the South Island and expose rocks of Cretaceous, Paleogene, and Neogene age. Based on the preservation of the specimen, it is considered most likely to originate from Manganui Beach. Most of the rocks here belong to the Tioriori Group, which is mostly Paleocene in age (and has produced an important assemblage of earliest Paleocene sharks from the Takatika Grit). Instead, there are deposits of the upper Eocene Te Whanga Formation. The specimen is admittedly not spectacular, but preserveds enamel ridges like Llanocetus, and a low, 'palmate' crown - rather than a high triangular one seen in basilosaurids. The tooth is quite a bit larger than the holotype of Llanocetus denticrenatus, but matches the size of gigantic teeth of Llanocetus sp. reported more recently from the same rocks in Antarctica.

Next up: baleen-bearing whales from the 'mid' Cenozoic of New Zealand.

References Cited