The Coastal Paleontologist down under

Odontocete trifecta in the latest issue of Journal of Vertebrate Paleontology

2013-05-16T05:23:00.005-06:00

I apologize for the lack of posts over the past month - the last few weeks I have been working furiously in order to complete a long list of manuscript revisions for a long manuscript for the journal Geodiversitas. Additionally, I've been trying to complete a laundry list of collaborations, which are slowly being completed. Now that I have breathing room again, welcome to the 200th post on Coastal Paleo (down under)!

Last week I was pleased to see the publication of not one, not two, but three different papers on cetaceans in the most recent JVP issue. I was also amused by the lamentation by some of my former fellow students from MSU that there weren’t enough dinosaur papers in JVP (one only!). It’s a welcome change, from my perspective – to be honest, roughly half of JVP issues have no marine mammal articles, and the majority have multiple (boooring…) dinosaur papers. To be fair, there are a hell of a lot more dinosaur researchers than there are marine mammal paleontologists, so it’s to be expected. On the other hand, despite the disappointment that comes with scrolling through brand new but marine mammal-less issues of journals, it does come with the upside that we often don’t have to add citations for numerous articles coming out while your manuscript is in review (unless it’s a long article that takes a while for review and revisions; I had a revised article I recently resubmitted which had taken about eight months from submission to completion of revisions, and I had to add citations for about a dozen new articles).

Comparison of Brachydelphis mazeasi (above) and Brachydelphis jahuayensis (below).

From Lambert and Muizon (2013).

The new studies are published by my colleagues Giovanni Bianucci and Olivier Lambert, and several of their European and South American colleagues. The first paper is by Olivier and prominent French paleocetologist Christian de Muizon on a new species of Brachydelphis from the Pisco Formation of Peru. The genus was named by Muizon (1988) who described Brachydelphis mazeasi, a short-beaked pontoporiid dolphin from the Cerro La Bruja vertebrate level of the Pisco Formation in Peru, a late middle Miocene locality. Pontoporiids today are represented only by the franciscana, aka La Plata River Dolphin, Pontoporia blainvillei. It’s my wife’s favorite cetacean, which she just refers to as “francis”. They don’t really look much like dolphins the public is familiar with – it’s got odd triangular fins and an elongate beak. It’s also tiny, topping out at 1.8 meters in length (5’ for American readers). It’s not quite as freaky looking as the Ganges/Indus river dolphin (Platanista; more on this one further down), or the Amazon river dolphin (Inia), and is actually pretty cute as far as cetaceans go (so is the Yangtze river dolphin, Lipotes). Note for the Californian readers: one of the most common fossil dolphins in California, Parapontoporia, was originally considered to be a franciscana relative, but is most closely likely related to the recently extinct Lipotes. One thing all modern river dolphins share in common, aside from generally plesiomorphic skull morphology, is an elongate and narrow rostrum. Platanista and Inia also retain what are arguably the least homodont dentition of any odontocete; modern river dolphins are sort of a relic of the Miocene fauna. Note: for the rest of the article, when you see the term “river dolphins” in quotes, I’m referring to all modern and fossil platanistids, pontoporiids, iniids, and lipotids; these taxa do not form a natural monophyletic grouping, and appear to have independently evolved (a topic for another post, I think).

The holotype (top) and paratype (bottom) of Brachydelphis jahuayensis from the

Pisco Formation of Peru. From Lambert and Muizon (2013).

Up until the description of Brachydelphis, all fossil “river dolphins” also shared an elongate rostrum (or, if not complete, the indication of an elongate rostrum) – Pontistes, Pliopontos, Ischyorhynchus, Parapontoporia, Zarhachis, Pomatodelphis, the list goes on and on. Brachydelphis on the other hand bore a tiny little rostrum, to the point where it must have resembled something like a true porpoise with weird flippers. A subsequent study reinterpreted the fragmentary Protophocoena minima from the Miocene of Belgium as a brachydelphinine (Lambert and Post 2005). The new study by Lambert and Muizon (2013) focuses on the description of a new species of Brachydelphis with a less stunted rostrum, and in a way is a bit more normal-looking. The rostrum of Brachydelphis jahuayensis, however, is still quite short relative to other “river dolphins”, and perhaps in that aspect still evocative of the name Brachydelphis. They reported on numerous new skulls which are preserved beautifully. The most fascinating aspect of the paper is the age of Brachydelphis jahuayensis – it’s from the El Jahuay vertebrate level of the Pisco Formation, which is younger than Cerro La Bruja, and thus younger than the shorter-snouted Brachydelphis mazeasi. Assuming an ancestor-descendant relationship (which I consider to be reasonable) between the two, it implies that Brachydelphis first evolved a short rostrum, and was then reversed during the late Miocene. It may not be surprising, as we already know that the cetacean rostrum is a fairly plastic feature that is readily adjusted to changes to feeding ecology (presumably, anyway). I actually was one of the reviewers for this paper, and I’m pleased to see it published. Interestingly, this younger, longer-snouted taxon was preliminarily recognized by Gutstein et al. (2009) from similarly aged strata from the Bahia Inglesa locality in Chile, which Lambert and Muizon (2013) referred to Brachydelphis jahuayensis.

Yet another skull of Brachydelphis jahuayensis. From Lambert and Muizon (2013).

The second paper is by the Italian paleocetologist Giovanni Bianucci on a new genus and species of oceanic dolphin from the Pliocene of Italy, Septidelphis morii. At first look, it is similar in overall proportions to many extant long beaked delphinines such as Stenella longirostris, and other Italian Pliocene delphinids such Etruridelphis giulii and Astadelphis gastaldii. It does differ from all other delphinids in having a fairly wide mesorostral groove, among other subtle features. Bianucci (2013) included it within a limited phylogenetic analysis which he used a molecular tree as a “backbone” constraint – in other words, forcing the extant species on the tree to conform to the molecular tree, and using the morphological characters to position the fossil taxa relative to the extant species. The analysis resulted in the recovery of Astadelphis, Etruridelphis, and Septidelphis as the earliest diverging delphinines, with the exception of extant Sousa chinensis. This information, in concert with molecular divergence dates, led Bianucci (2013) to suggest that perhaps extant genera of delphinids may be nearly lacking entirely in the Pliocene, and that aside from a few cases of extinct species in extant genera (e.g. Orcinus citoniensis), most modern lineages probably did not originate until the Pleistocene. One piece of evidence for this is that the majority of nodes in the molecular phylogeny of extant delphinids occur in the Pleistocene (again, based on molecular divergence dating). To summarize, this suggests perhaps an even more rapid divergence among delphinids than has been previously hypothesized.

The holotype cranium of Septidelphis. From Bianucci (2013).

The last (and shortest) paper is on a single earbone, also by Giovanni Bianucci, Olivier Lambert, and colleagues. This paper reports a fossil earbone of a platanistine river dolphin – closely related to the modern Ganges River dolphin – from the Amazon river basin in eastern Peru. A Ganges River dolphin relative in South America. How cool is that? It’s also only the second reported platanistine fossil ever – the first is an admittedly less convincing chunk of mandible from the early Miocene Nye Mudstone of Oregon. This new earbone is fairly strange looking (a requirement for a platanistine, to be honest), with a long and strangely curved anterior process. It shares several feature with modern Platanista. This specimen is middle Miocene in age, and indicates that platanistines used to inhabit South America. One of the more interesting aspects of this earbone is where it was preserved, environment wise: it’s found with a number of terrestrial mammals, and occurs in fluvial-lacustrine deposits with occasional marine influence. Fossils of freshwater cetaceans are notoriously rare, and include some eurhinodelphinids material from Australia (Fordyce, 1983; possibly platanistoid, according to research presented by Erich Fitzgerald at the 2010 SVP meeting), Ischyorhynchus from South America (Cozzuol, 2010) and some Pomatodelphis material from Florida. Bianucci et al. (2013) proposed the following sequence of events in the biogeographic history of Platanista: platanistines evolved in the Pacific as primarily marine odontocetes, with some becoming adapted to freshwater environments of the Amazon basin during the middle Miocene, and finally dispersing and adapting to freshwater environments of southern Asia (Platanista), with all other platanistines (as yet unknown) becoming extinct. Interestingly, where the platanistine fossil occurs is now inhabited by the Amazon river dolphin, Inia geofrrensis. Bianucci et al. (2013) also noted that an odontocete historically regarded as an iniid, Ischyorhynchus, was recovered as the sister taxon to Platanista in the Geisler et al. (2012) cladistic analysis. Further analysis is required to be sure, as many taxa jump around depending upon the type of analysis and changes in coding, but it is a tantalizing possibility that two platanistines may have been in Miocene rivers of South America.

The fossil platanistine periotic (left), compared to a modern Platanista gangetica periotic (right). From Bianucci et al. (2013).

References cited

Bianucci, G. 2013. Septidelphis morii, n. gen. et. sp., from the Pliocene of Italy: new evidence of the explosive radiation of true dolphins (Odontoceti, Delphinidae). Journal of Vertebrate Paleontology 33: 722-740.

Bianucci, G., Lambert, O., Salas-Gismondi, R., Tejada, J., Pujos, F., Urbina, M., and Antoine P.O. 2013. A Miocene relative of the Ganges River dolphin (Odontoceti, Platanistidae) from the Amazonian Basin. Journal of Vertebrate Paleontology 33:741-745.

Cozzuol, M. A. 2010. Fossil record and the evolutionary history of Inioidea; pp. 193–217 in M. Ruiz-García and J. Shostell (eds.), Biology, Evolution and Conservation of River Dolphins within South America and Asia. Nova Science Publishers, New York.

Fordyce, R.E. 1983. Rhabdosteid dolphins (Mammalia: Cetacea) from the middle Miocene, Lake Frome, South Australia. Alcheringa 7: 27-40.

Geisler, J. H., S. J. Godfrey, and O. Lambert. 2012. A new genus and species of late Miocene Inioid (Cetacea, Odontoceti) from the Meherrin River, North Carolina, U.S.A. Journal of Vertebrate Paleontology 32:198–211.

Gutstein, C. S., M. A. Cozzuol, A. O. Vargas,M. E. Su´ arez, C. L. Schultz, and D. Rubilar-Rogers. 2009. Patterns of skull variation of Brachydelphis (Cetacea, Odontoceti) from the Neogene of the southeastern Pacific. Journal of Mammalogy 90:504–519.

Lambert, O., and Muizon, C. de. 2013. A new long-snouted species of the Miocene pontoporiid dolphin Brachydephis and a review of the Mio-Pliocene marine mammal levels in the Sacaco Basin, Peru. Journal of Vertebrate Paleontology 33:709-721.

Muizon C. de 1988. Les vertébrés fossiles de la Formation Pisco (Perou). Troisieme partie: Les odontocètes (Cetacea, Mammalia) du Miocène. Editions Recherche sur les Civilisations 78: 1-244.

Otago Daily Times press release image

2013-04-21T06:03:00.002-06:00

I was told by reporter John Gibb of the Otago Daily Times (called the ODT by locals) that the graphics department at the paper would be making a modified version of the image/infographic I had already put together. I was pretty surprised with how their modified version looked - it's pretty spiffy, with an admittedly more visually pleasing color scheme (...or "colour" I should say). Here it is:

Further reading:

Boessenecker, R.W. 2013. Pleistocene survival of an archaic dwarf baleen whale (Mysticeti: Cetotheriidae). Naturwissenschaften 100:365-371.

Research Links Whales - April 13, 2013, Otago Daily Times

Stay tuned! More in a few days (on newer subjects).

New publication, or - The little whale that (almost) could: survival of Herpetocetus in the Pleistocene

2013-04-15T22:30:00.001-06:00

Last week saw the publication of my most recent article, a short paper in Naturwissenschaften regarding a new specimen of the archaic baleen whale Herpetocetus from Northern California. The new fossil is surprisingly young in geological terms for this genus – early to middle Pleistocene. In this post I’ll discuss the new specimen and its implications, as well as what exactly we know about the Pleistocene epoch in terms of marine mammals. But before I talk much further about this study, I’ll need to briefly introduce you to two different back stories.

Front page of the new publication in the journal Naturwissenschaften.

The first backstory is a discovery I made in June 2007 – I spotted the cross-section of a baleen whale rostrum in a sandstone cliff of the Purisima Formation near Santa Cruz. The tide was coming in, and it would clearly take several afternoons to excavate – and in any event, I had no idea which way the skull was pointing; it could have just been the rostrum, which would be way less interesting than if it were everything behind the rostrum – the braincase and earbones, which are certainly the most informative part of a cetacean skeleton. The rostrum is informative as well, but there would not have been much left given the way it was exposed. Fortunately, I found a small boulder on the beach which appeared to include part of the rostrum, matching the cross section in the cliff. I wrapped it up and took it home – once prepared, it could tell me which direction the skull was facing, and which end of the skull was in the cliff. Preparation of this section indicated that the posterior part of the skull was in fact in the cliff – so I returned two weeks later, and dug out the skull with my friend Chris Pirrone. It was easy to excavate, but a pain to remove – we finished the jacket at 6pm as the tide was coming in, and it took us four hours to move the ~150 lb jacket a measly 300 feet. During this period of time, the jacket spent about fifteen minutes in the surf while I rethought my life and doubted the outcome of the excavation. Chris’ optimism saved the fossil – and the floormat from his car as well, which we used as a makeshift stretcher. A few months later, back in Montana (this was the last year of my bachelor’s degree), I had the fossil mostly prepared. It included the entire posterior one-half of a skull, with both petrosals and one tympanic bulla – and even all three middle ear ossicles (malleus, incus, and stapes). At the time, no known skull of Herpetocetus was yet known – but I knew it was something similar to Piscobalaena. The fossil which would later become Herpetocetus bramblei, named by Whitmore and Barnes (2008), was figured in Barnes’ doctoral thesis (1976) – and was identical to my new specimen, in addition to being from the same locality. As it turned out, I only needed to wait a year until the species would be published, and it became immediately recognizable as Herpetocetus bramblei, albeit much more complete than the holotype. This discovery (now curated and cataloged as UCMP 219111 at UC Berkeley) catapulted me into the study of Herpetocetus and other cetotheriids, and I started to find additional fossils of this whale everywhere.

The second part of the backstory started when I was in high school. There used to be a website titled “Collecting Fossils in California” at www.gtlsys.com, which I used to contact other fossil collectors and find fossil sites to visit. Other much more experienced collectors posted pretty incredible fossils they had found, from all over the US – but mostly from the west coast. One collector in particular – Ron Bushell – lived at the time in Eureka in Humboldt County in Northern California, and had for years been finding incredible marine invertebrate and marine mammal fossils from Plio-Pleistocene strata in Northern California. When I first visited the website in 2004, Ron posted some sort of an odd bone he had partially prepared out of a sandstone nodule from the Scotia Bluffs locality along the Eel River. I had no idea what the find was at the time – and nobody else did either; some had suggested it might be from a seal, or a sea cow, or even a cetacean. It surprised me that there was no single, comprehensive collection of comparative images of bones and teeth from all groups of marine mammals. At the time, to a high school student who had assumed fossil marine mammals had attracted just as much study as dinosaurs – it seemed like a reasonable assumption that such a volume existed. Unfortunately, it does not. In 2007, I visited the Chapman’s rock shop where the fossil currently resides – and identified it as a calcaneum of a large walrus. Since my days in high school, Ron and I have been good friends, and he gave me all sorts of expert advice on California fossil sites. Ron made numerous other discoveries, including some fur seal mandibles I published in JVP in 2011 (Boessenecker, 2011). Several of his other discoveries will prompt further scientific study, including some Pleistocene sea otter fossils, and a walrus forelimb from Crescent City, California. Ron moved to Montana during my Sophomore year of college, and although he did visit campus once, I unfortunately never had a chance to get out to his ranch near Helena – the road would be snowed in by the end of September when I arrived in Bozeman, and would remain snowed in nearly until I finished in the spring. One of his finds I saw for the first time in January 2007 on a visit to Sierra College – a small baleen whale skull in a hefty calcareous sandstone nodule.

The skull as I first saw it in the Sierra College prep lab in 2007, still with a fair

amount of calcareous matrix attached.

The fossil was donated by Ron to Sierra College in Rocklin, California, where Dick Hilton and George Bromm began preparing the specimen – slowly. The sediment was so damn hard, but fortunately soluble – and they were able to slowly acid prepare the specimen with over the counter vinegar from the grocery store. Acid preparation took the better part of a decade, and was finally completed in 2011. When I first saw the specimen, I thought it looked remarkably primitive, and thought based on the triangular supraoccipital shield – thought it was a middle Miocene “cetothere” (aka “Kelloggithere”). You can imagine my shock when Dick Hilton told me that the fossil was from the Pleistocene Falor Formation – it looked to be about 10 million years too young! To be fair, I had not yet discovered the Herpetocetus skull from Santa Cruz, and didn’t really know how to recognize the taxon.

Comparison of UCMP 219111, the skull of Herpetocetus bramblei I collected in 2007 (and am currently/still studying), and the Pleistocene Herpetocetus sp. from Humboldt County.

After another year or two of study, it became clear in my mind that Herpetocetus was the last remaining true cetothere living in the eastern North Pacific (and probably the Northern Hemisphere). Herpetocetus is present in very late Miocene and Pliocene strata from California – including the San Mateo and San Diego Formations of southern California. Herpetocetus is also found in the early Pliocene Yorktown Formation of North Carolina, as well as the early Pliocene of Belgium and Japan. The youngest known Herpetocetus – according to the literature – was from the mid-late Pliocene San Diego Formation, approximately 2-3 million years in age.

The skull of VMS-65 and a locality map (Fig. 1 from Boessenecker, 2013).

I returned to Sierra College in 2008, and although the fossil needed a fair amount of preparation – quite a bit of calcareous sandstone still remained – I recognized the specimen as Herpetocetus, instead of a “kelloggithere” from older rocks. I asked Dick Hilton if I could take the fossil on loan for a few weeks – I had a visit to the San Diego Natural History Museum, the primary purpose of which was to make some comparisons with Herpetocetus material – skulls, mandibles, earbones – at the SDNHM – ahead of my first talk at the annual SVP meeting, which was coming up in October (read here for some information about that talk). Dick agreed, and I brought the Falor Formation specimen along with the referred Herpetocetus bramblei skull to show Dr. Tom Deméré, the paleontology curator at the SDNHM. Tom was fairly surprised to about the Pleistocene specimen – and agreed with my identification (satisfying for a young researcher). It would be three more years, however, until I saw the specimen fully prepared; each time I visited Sierra College, a little more matrix had been dissolved away. Finally, in summer 2011, the last remaining matrix had been removed from the earbone, and study of the fossil was able to commence. The fossil shares a number of features with Herpetocetus bramblei and others – including maxillae that “squeeze” out the premaxillae and thus contact each other medially on the front of the braincase, just posterior to the bony naris. That may sound a bit technical, but this is an unusual feature in baleen whales and unique to whales like Herpetocetus, Piscobalaena, and Nannocetus. Two other features, present in one of the earbones – the petrosal (the one which houses the cochlea and semicircular canals) – had two projections only found in Herpetocetus. One, the anterior process – is tapered and bladelike; in most other mysticetes, this process is blunt. The other feature – the lateral tuberosity – is triangular and projects truly laterally (i.e. towards the side of the skull), whereas in most mysticetes it faces ventrally when the bone is in the skull still – and it underlaps the squamosal bone of the skull, a condition unique to Herpetocetus (and possibly in Caperea as well; e.g. Fordyce and Marx 2012). Because the fossil is relatively incomplete, I was only comfortable identifying the fossil to Herpetocetus sp.

The earbones of Pleistocene Herpetocetus sp. specimen VMW-65 above and Herpetocetus bramblei below (Figure 2 of Boessenecker, 2013).

Before I continue, a few words about the Falor Formation. It’s exposed in a narrow NW-SE directed belt inland of Arcata in Humboldt County, California. It’s predominantly shallow marine, and was deposited in a long embayment presumably separated by headlands from the larger Eel River Basin to the south. The Eel River Basin began to subside around the Mio-Pliocene boundary, depositing the absurdly thick Wildcat Group, starting with the Pullen Formation (latest Miocene-early Pliocene, Purisima Fm. equivalent) and ending with the middle Pleistocene Carlotta Formation, which appears to be conformably overlain by late Pleistocene coastal sediments. Now, within the Falor basin, there are no marine rocks exposed older than latest Pliocene; the Falor Formation unconformably overlies Mesozoic basement rocks. An ash bed lies near the base of the Falor Formation; this ash has been chemically fingerprinted and matches the Huckleberry Ridge Tuff, a well known 2.1 Ma eruption of the Yellowstone supervolcano. While at MSU, we went on several field trips where we went and looked at the tuff itself and associated basalt flows; the eruption was so large that ash traveled far enough west to reach the Pacific coast (correlative ash has also been found in deep sea cores from the middle of the North Pacific, suggesting it traveled around the earth by prevailing winds before being deposited on the seafloor). This 2.1 Ma date provides the lower age boundary for the new Herpetocetus fossil. Because little syndepositional folding/deformation of the Falor Formation is known, deposition is interpreted to have been completed by 700,000 years, when deformation associated with the Mad River fault zone became active. This provides an age range of 2.1 Ma to 700 Ka for the Falor Formation Herpetocetus.

Examples of some of the weirdness in Pliocene marine mammal faunas: Denebola brachycephala, technically Miocene but present in the Pliocene of California as well - a warm-water beluga relative, now extinct; Callorhinus gilmorei, a very modern-looking pinniped but quite a bit smaller than its modern descendant; Odobenocetops, the walrus faced whale - 'nuff said; Acrophoca, the long snouted seal from Peru/Chile; and Auroracetus, a relative of the modern La Plata river dolphin, but from the Pliocene Yorktown Formation of North Carolina. I could include many more examples, but they wouldn't fit.

Time to switch gears, and give some context to Herpetocetus in the Pliocene. The Pliocene was a time of change – although I suppose you could probably say that about any epoch, really. The Pliocene was a transitional period between the warm climate of the Miocene and the icy climate of the Pleistocene. The Tethys and Paratethys seaways finally closed up, the Panama land bridge formed, causing changes in global circulation and upwelling – followed by increased northern hemisphere glaciation and cooling climates. Pliocene marine mammal assemblages were a bit of a weird mix – definitely a transitional assemblage between that of the Miocene and the Pleistocene, but not in the same sense as climate and geography. Pliocene marine mammal assemblages include a menagerie of species of modern and archaic aspect. Archaic marine mammals include late surviving “Scaldicetus”-grade sperm whales (more on this below), dusignathine walruses (such as Dusignathus seftoni), albireonid dolphins (Albireo savagei), and others. Herpetocetus technically falls in this category (but read further). The Pliocene is also the first appearance of many modern genera – in the Pacific, Eschrichtius (the gray whale), Balaenoptera (rorqual whales), Tursiops (bottlenose dolphins), Callorhinus (northern fur seal), and Hydrodamalis (Steller’s sea cow) all appear during the Pliocene. In the Atlantic, Balaena (bowhead whale), Megaptera (humpback whale), Lagenorhynchus (white-sided and related dolphins), Pseudorca (false killer whale) and other modern critters show up.

Three broad groups further adding to the Pliocene “mix” existed (some members of the aforementioned archaic and modern groups outlined above may also fit into these latter three categories). The first are members of extant groups with wildly different biogeographic ranges than today. This includes beluga relatives adapted to temperate and subtropical waters of the Pacific and Atlantic (Denebola from Baja California and Bohaskaia from North Carolina, for example), South American “river dolphins” in North America (the pontoporiids Auroracetus bakerae, cf. Pontoporia), Asian ‘river dolphins’ in North America (the lipotid Parapontoporia), and tusked odobenine walruses in temperate and subtropical waters (Valenictus in southern California and Baja, and Ontocetus in the Carolinas, Florida, and Morocco). These discrepancies in distribution indicate that some unknown process drove rather extreme changes in marine mammal biogeography. The second of these groups are close relatives of modern marine mammals – either within the same genus or in closely allied genera – that are dwarfs relative to modern species; examples include the fur seal Callorhinus gilmorei, the dwarf right whale Balaenula, and various small-bodied species of Balaenoptera (e.g. “Burtinopsis” from Japan). The last group are marine mammals with seemingly bizarre or novel adaptations, which seem to be more prevalent in Pliocene oceans than today. These include the sharp-snouted seal Acrophoca, double-tusked walruses like Dusignathus, the aquatic sloth Thalassocnus, the walrus-faced whale Odobenocetops, the strange “skimmer porpoise” from the San Diego Formation, and the ziphiid-convergent dolphin Australodelphis from Antarctica. Herpetocetus is pretty strange, and given the unique configuration of its jaw joint, which prohibited it from opening its jaws much past ~30 degrees – so Herpetocetus sort of belongs to this ‘bizarre’ category as well. To conclude – although strange, Herpetocetus more or less fits with what we know about this motley crew of strange marine mammals of the Pliocene ocean.

Stratigraphic range of various cetotheriids, with Herpetocetus range extension bolded (Fig. 3 of Boessenecker, 2013).

In contrast, the Pleistocene fossil record of marine mammals – as crappy as it is – is nearly entirely composed of modern genera and species (or extinct species within modern genera). Some exceptions include the strange globicephaline pilot whale Platalearostrum (possibly Pliocene in age) and the sea lion Proterozetes ulysses (probably a species referable to Eumetopias). Previously published baleen whales from the Pleistocene include humpbacks and other rorquals from Japan (Megaptera, Balaenoptera), gray whales from California (Eschrichtius), and bowhead whales from the arctic and north atlantic (Balaena). Another important distinction is that the Pleistocene is the first period in the history of cetaceans when most baleen whales trended towards the gigantic body sizes we see today. Indeed, if you only go as far back as the Pliocene, most mysticetes are comparatively small; in the San Diego Formation assemblage, there is a big ~10-15 meter balaenopterid, and a similarly sized eschrichtiid – and all other mysticetes are smaller in size, right down to diminutive Herpetocetus at roughly 4 meters. So there are giants in the Pliocene (and late Miocene), but they are rare, and on average body sizes are much smaller. With these two pieces of information in hand – the dominance of extant species in the Pleistocene and the trend towards modern gigantism – a picture is painted of the modern baleen whale fauna appearing in the Pleistocene after the members of the strange Pliocene fauna went extinct.

Press release image for the study showing the stratigraphic range of familiar marine and terrestrial mammals from the Pacific coast of the United States; I put this together as a sort of infographic, using part of a life restoration I borrowed from another project.

Enter Herpetocetus – a stranger in a strange land, if you will. A peculiar little whale that couldn’t open its mouth very far open, dwarfed by more recently evolved giants, in a rapidly cooling ocean. Why did Herpetocetus persist so much longer than other members of the Pliocene fauna? For one, the Pleistocene record is so terrible, we don’t know if other Pliocene taxa held on for longer – and this new fossil suggests, maybe they did. However, what we do know, if we look outside cetaceans, is that the modern pinniped assemblage had already appeared in this region. Based on the California and Oregon fossil record, we already have fossils of modern California and Northern Sea Lions (Zalophus and Eumetopias, respectively), harbor seals (Phoca), with elephant seals (Mirounga) to follow in the late Pleistocene. The sea otter Enhydra also first appears during the middle Pleistocene, presumably an immigrant from Asia. We don’t know much about Pleistocene odontocetes in this region – but nevertheless, it appears as though Herpetocetus persisted alongside many marine mammals familiar to us today. The occurrence of Herpetocetus in the Pleistocene suggests two separate possibilities: either Herpetocetus was (even more) unusual and persisted alongside modern species after an extinction of marine mammals at the end of the Pleistocene – in which Herpetocetus can be viewed as a “lost” member of the modern fauna (like the Steller’s sea cow) that almost survived – or, this discovery indicates that the Plio-Pleistocene pattern of faunal turnover among marine mammals was more complex than previously noted. To be fair, nobody has really attempted to address this issue before (one exception would be Valenzuela-Toro et al., 2013).

Another interesting aspect of this study is what it means for the hypothesis that the pygmy right whale, Caperea marginata, is an extant cetothere. In the Fordyce and Marx (2013) phylogenetic analysis, Caperea appears as a sister taxon to Herpetocetus and Nannocetus, and is deeply nested within the “true” cetotheres. The presence of one of these putative sister taxa within the Pleistocene lends some indirect support, by establishing the plausibility of one of these cetotheres surviving to the modern era. If Herpetocetus (a proven cetothere) could survive to within the last one million years, then Caperea – tentatively identified as a cetothere – plausibly could have survived as a member of that group. In the paper I went so far as to highlight Herpetocetus as a northern hemisphere analog of Caperea – in a way, both are tiny, have weird anatomy, and are far removed from other contemporary cetaceans in the northern and southern hemispheres, with no close relatives, presumably doing something weird and different in terms of behavior and ecology. I'd love to talk about the feeding strategy and mechanism for the extinction of Herpetocetus, but that research isn't quite finished yet.

So what’s next? More Herpetocetus research is on its way (including new species!), as is a much, much larger study of Plio-Pleistocene faunal change in marine mammals. So, stay tuned.

This study in the news:

Research links whales - Otago Daily Times 4/13/2013

Dwarf whale survived well into Ice Age - Science Daily 4/4/2013

Otago Research reveals dwarf whale survived well into Ice Age - University of Otago press release 4/5/2013

Dwarf whales lived during Ice Age - Redorbit, 4/5/2013

References:

Boessenecker, R.W. 2013. Pleistocene survival of an archaic dwarf baleen whale (Mysticeti: Cetotheriidae). Naturwissenschaften 100:4:365-371.

Fordyce, R.E., Marx, F.G. 2012. The pygmy right whale Caperea marginata-the last of the cetotheres. Proceedings of the Royal Society B 280:20122645.

Valenzuela-Toro AM, Gutstein CS, Varas-Malca RM, Suarez ME, Pyenson ND (2013) Pinniped turnover in the south Pacific Ocean: new evidence from the Plio-Pleistocene of the Atacama Desert, Chile. J Vertebr Paleont 33:216–223.

Whitmore FC, Barnes LG (2008) The Herpetocetinae, a new subfamily of extinct baleen whales (Mammalia, Cetacea, Cetotheriidae). Va Mus Nat Hist Spec Pub 14:141–180

Paleo research on the University of Otago homepage

2013-04-10T03:36:00.003-06:00

Hello all,

Now that the Oregon road trip has been sufficiently covered I can get back to covering recent events. About a week or two ago I got a new paper published in the journal Naturwissenschaften, regarding a surprisingly late occurring record of the archaic baleen whale Herpetocetus. I don't enough time to talk about it now, but the press release made it onto the University homepage, which was a pleasant surprise.

In addition to the new paper, three other cetacean related stories had been posted up on the homepage as well. Go ahead and check them out. Here's the official press release on the University website (although the entire OU website is offline, at the moment).

Boessenecker, R.W. 2013. Pleistocene survival of an archaic dwarf baleen whale (Mysticeti: Cetotheriidae). Naturwissenschaften 100:4:365-371. Link to article on Springer.com.

Oregon coast trip with Ray Troll and Kirk Johnson, part 3: Newport Aquarium, Sea Lion Caves, and Finale

2013-04-07T01:54:00.003-06:00

Sorry for the delay in posting (again); it's been busy, and I have a couple of new papers I really ought to talk about (and soon). Stay tuned!

On our third day in Oregon, it was a bit too rainy to try visiting field localities again, so we spent some time at Kirk and Ray’s cabin at the Sitka Center discussing fossil marine vertebrates from the Pacific coast. Ray wanted to illustrate marine faunas from three different periods for their book, so we chatted for a few hours about how best to divide those faunas. If I remember correctly, I think we settled on the late Oligocene assemblage represented by strata from the Newport Embayment, the middle Miocene as represented by the Sharktooth Hill Bonebed, and latest Miocene and Pliocene assemblages as represented by the Purisima/Capistrano/San Mateo and San Diego Formations. We discussed for a while how to illustrate some of the stranger fossil marine mammals, such as aetiocetids, the walrus Gomphotaria, the bony toothed bird Pelagornis, and others. After a few hours, we visited a rock shop in Lincoln City and explored the town a little bit. We had lunch at “Pronto Pups”, which claimed to have invented the corn dog in 1946. Kirk looked this up later that day, and apparently there are older claims (Carl and Neil Fletcher, Texas State Fair, 1938-1942; Pronto Pup vendor at Minnesota State Fair in 1941; Cozy Dog Drive In, Illinois, 1946; and Hot Dog On a Stick in Santa Monica, 1946). I’ve never really liked corn dogs so the experience was lost on me anyway.

Frank's blue whale mandible cast.

We spent the rest of the afternoon and evening at the Sitka Center where Frank Boyden showed us his workshop and some more of his amazing stuff he’s made and accumulated over the years. One thing which was in his garage was something he put together for a party at his house: a simple machine using a huge pipe and special lighting to simulate the rare optical phenomena called the “green flash” – the greenish flash appears just after the sun sets on rare occasions. The viewer sits at one end of the tube and drapes a blackout cloth over them, while a cut out at the other end is slid down (with a light source behind) by Frank. He took us to a (large) shed, and showed us a cast of a blue whale mandible he made sometime in the 1990’s – it was just shy of 20 feet long or so. It was originally intended to be cast in bronze for the Oregon Coast aquarium in Newport, but things didn’t work out.

Beautiful bronze bird head door handles at the aquarium, done by Frank.

An impressive feat for such a heavy animal - the adult male California Sea Lion (Zalophus californianus).

On our last day in Oregon, we left early to make a visit to the Oregon Coast Aquarium in Newport. Frank made some amazing sculptures at the aquarium, which Sarah and I had previously seen and appreciated on a visit in 2009, long before meeting Frank. The sculptures include large blocks of rocks in bronze – some which appear to have been large concretions found on the shoreline – with whale bones, mussels, barnacles, fish, and other sea creatures. Several years prior, Ray had an exhibit at the aquarium, so we visited a few old friends and got a behind the scenes tour – including feeding and petting a giant Pacific octopus. The octopus was pretty friendly, and according to staff, a bit of a troublemaker; an awesome sign was posted on the side of the tank saying “Do not taunt the octopus”. I found the suckers to be surprisingly powerful – one was stuck on one of my fingertips and after a few seconds of trying to pull my hand away it began to hurt a little. At one point Sarah was trying to photograph the octopus and it squirted a couple liters of water up at us – drenching my jacket and Sarah’s pants, and camera. Even though it was saltwater her camera was alright. A few minutes later we watched the staff feed the hagfish – which, as a taphonomist, was pretty awesome. Lastly, we went outside and got to meet their adult male sea lion up close and personal. We all got kissed by the sea lion, which was pretty awesome – Kirk took his on the lips, which was hilarious. It was great being that close to one of the animals I study.

You've been warned!

The octopus, pre-squirting. So cool! Enteroctopus dofleini.

Incredible sculpture by Frank - whale bones emerging from the rock. In the photo on the right, try and spot one rib that's 'different'.

Have I ever looked so happy?

After leaving the aquarium, we left Newport and continued south for some more sea lion goodness at Sea Lion Caves just north of Florence, Oregon. The operators of Sea Lion Caves boast that it is the World’s largest sea cave, and the only mainland rookery of Steller’s sea lions in North America. The cave itself is formed by two cross-cutting dikes at a roughly 90 degree angle, which are weaker than surrounding rocks and have been preferentially eroded. The cave actually has three openings: the large west facing opening, and smaller north and south facing openings. The north opening grants a unique view of the Heceta Head lighthouse. The cave was discovered in 1880 by William Cox, who piloted a small boat into the large western opening on a calm day. After watching waves explode into the entrance for only a few minutes I decided that Mr. Cox must have been criminally insane. Apparently he visited the cave a number of times and on one occasion got stranded by rough weather, and he shot and killed a sea lion for sustenance. Cox purchased the land in 1887. In 1927 the property was purchased from the Cox family, and subsequently three gentlemen by the names of Clanton, Houghton, and Jacobsen thought to turn it into an attraction and began construction of a walkway to the north entrance; by the 1940’s it had become a popular attraction, and in 1961 an elevator was added – the same you take down to the cave nowadays. The cave houses a large number of Steller’s sea lions, one of my favorite pinnipeds – and a difficult one to spot in California waters. My first Steller’s sighting was at the Santa Cruz Lighthouse in 2007 – I spotted two gigantic males fighting for territory on the small rock lying ~ 100 meters south of the lighthouse; they dwarfed the female California sea lions which normally haul out on that rock. Sarah and I had first visited Sea Lion Caves on a long road trip from San Francisco to Astoria and then eastward back to Montana – but we had visited in August, and there were no Steller’s sea lions in the cave. We tried looking from some overlooks north along highway 101 towards Heceta Head, but only saw California sea lions. It was a major disappointment for us.

The main cavern at Sea Lion Caves; the main west entrance is to the right, and the small south entrance is in the right center. If this isn't a real life "Goonies" moment, I don't know what is.

The north entrance, with Heceta Head barely visible through the fog. Check out that surf!

When we visited this time, however, it was in February and practically a goddamned circus – it was smelly, loud, and wonderful. Every sort of bark, growl, snort, sneeze, and other audible bodily function contributed to a bizarre chorus. When you get out of the elevator, you walk into a small chamber with a viewing platform, raised above the main cave, separated from the sea lions by a chain link fence. There’s low lighting, and there are numerous signs telling visitors to stay quiet, and a guard to make sure people don’t harass the sea lions – along with plenty of information panels, and even a subfossil adult make Steller’s sea lion skeleton surrounded by a railing. Unfortunately, somebody stole the skull many years ago.

An adult female Steller's sea lion (Eumetopias jubatus) skeleton mounted on display. It used to be in a cabinet (and is one of the most popular results on google images for searching "sea lion skeleton", but the lighting is arguably more awesome now.

After Sea Lion Caves, we said our goodbyes to Kirk and Ray, and began our trip back down south to San Francisco. After all, we had only a week and a half until we would get on a plane and fly to New Zealand, and we still had plenty of packing to do. We only had two important stops left: we had to stop at a Pleistocene marine mammal locality, and make a quick pitstop at Prehistoric Gardens to take a couple ridiculous photos. Unfortunately, I didn’t find a damn thing at the fossil site, so I headed back to the car where Sarah was taking a well deserved nap, and continued to Brookings, Oregon, where we got a delicious seafood dinner, and eventually stayed the night in Crescent City.

Fog rolling in, and the sun going down at the fossil site. By the time I got back to the car it was damn near dark, and I had to call Sarah to turn on the headlights so I could see where the road up the hill was.

A large cluster of Pleistocene barnacles (Balanus) at the locality.

A quick stop at Prehistoric Gardens allowed for a hilariously bogus Jurassic Park like photo.

Roosevelt Elk in Humboldt County, right off Highway 101.

Oregon coast trip with Ray Troll and Kirk Johnson, part 2: fossil localities of the Newport Embayment

2013-03-17T00:50:00.001-06:00

We got up early the following morning to prepare for a long day of field work. We had some ambitious plans: we were to check out three of Doug Emlong’s fossil localities, all in one day. This included an area south of Depoe Bay, and the well-known Moloch (pronounced Moolack) Beach north of the Newport Lighthouse. These localities are all exposures of various units deposited within the mid-Cenozoic Newport embayment, an ancient basin that occupied what is now the central Oregon coastline, from Waldport to Lincoln City (or further; I’m unclear as to the limits of the depositional package, but it certainly does not continue to Astoria, as mid-cenozoic rocks in this region are considered part of the Astoria embayment). Marine rocks in coastal Oregon have yielded a substantial assemblage of fossil marine mammals, among other marine (and terrestrial vertebrates). Indeed, we owe much of our knowledge of marine vertebrates from this time and place to the dogged perseverance (if not outright obsession or addiction) of Emlong, and other collectors who followed him like Guy Pierson and James and Gail Goedert. The three formations we visited were the ‘middle’ Oligocene Yaquina Formation, the late Oligocene-early Miocene Nye Mudstone, and the late early-early middle Miocene Astoria Formation. FYI, some paleontologists – myself included prior to this trip – assume that it’s Spanish in origin and pronounced “Yakeena”. Turns out it’s pronounced “Yakwinna”, and it’s named after the nearly extinct Yaquina Indians; an alternate spelling of their language is actually Yakwina. Anyway, now you know. There’s a Yaquina bay, Yaquina Formation, and the Yaquina lighthouse.

Ray and I discuss the finer points of desmostylian posture while Kirk does something practical.

Ray and I are still discussing desmostylian posture while waiting for a table at the Otis Cafe.

The spouting horn at Depoe bay, Oregon. We stopped to check this out on our way to the localities.

Before we left for the field, we drove from the Sitka Center to the local favorite ‘Otis Café’. Over an enormous breakfast consisting of the world’s best fench toast and bacon, Ray, Kirk, Sarah, and I discussed the intricacies of reconstructing the posture of desmostylians. Frank Boyden joined us a little late for breakfast. On a whim, Kirk asked the waitress if she knew who Emlong was – and as it turned out, her sister had been a girlfriend of Emlong’s. Apparently, he had asked her out after high school, and she wasn’t interested. He tried again after he got his first payment for his Smithsonian collecting job (which he started in 1967), and bought a car – and then she went out with him. I made sure to buy a T-shirt from the establishment before we left Lincoln County.

Kirk and I put together a plan for the day at our first stop.

Although we didn't find any fossils, a walk on the beach is likely to turn up all sorts of evidence of modern dead critters - a tufted puffin carcass, in this case. We spotted about a dozen seabird carcasses, including several puffins (Fratercula), murres (Uria), and cormorants (Phalacrocorax).

Kirk has a habit of scampering up the nearest promontory.

Another puffin.

Our first stop was the Yaquina Formation. Emlong collected a number of significant fossils from the Yaquina – by far the most important of which is the type and only known specimen of the toothed mysticete Aetiocetus cotylalveus (not cotylaveus). The holotype skeleton was collected by Emlong in March 1964, and includes a well preserved skull, most of a vertebral column (39 vertebrae), 23 ribs, several loose teeth, part of a sternum, and several chevrons. Emlong originally considered it to be an archaeocete, given the presence of teeth and the lack of derived mysticete features. The remarkable thing is that Emlong, with zero technical background in paleontology – with encouragement from J. Arnold Shotwell and Remington Kellogg – described and named the fossil himself, in his only publication – less than two years after the fossil was dug out of the rock on the beach. It was later identified by Leigh Van Valen as a primitive baleen whale (but I’ll talk about that in a separate post). Other finds from the Yaquina Formation included the holotype of the primitive desmostylian Behemotops emlongi, named after Emlong (later synonymized with Behemotops proteus from the Olympic Peninsula in Washington; this taxon is sort of the “Pakicetus” of desmostylians), and skulls and mandibles of the more derived desmostylian (with a fabulous name) Cornwallius sookensis, which were eventually described by my good friend and colleage Brian Beatty (the species was originally named from the Sooke Formation on Vancouver Island, British Columbia). Lastly, the early pinniped Enaliarctos tedfordi was described from this locality by Annalisa Berta in 1991. Emlong collected the holotype of this specimen – a complete skull – in 1964. We looked around for about a half hour, and didn’t find a damn thing. Then again, the sand level was pretty high.

Sarah at Moloch Beach with the Astoria Formation in the background.

We moved to the next locality, a couple miles north – to examine additional outcrops of the Yaquina Formation and the late Oligocene-early Miocene Nye Mudstone. This was near the type locality of Enaliarctos mitchelli, which is from right around the Oligo-Miocene boundary. There was plenty of fossilized wood – probably limonitized or mildly pyritized, as indicated in Emlong’s paper. That’s about all that we found in either the Yaquina or the Nye, though. Despite a long history of important fossil discoveries from this locality, I was beginning to get disappointed with how poorly fossiliferous the localities were – I’m used to fossil localities in central California where literally hundreds of bones, teeth, and bone fragments are found for every skull that is recovered – and on a single trip, a hundred vertebrate fossils can be found after less than an hour of looking. We had visited two localities that had yielded several holotype specimens each, and not found a shred of bone.

Sarah wading through a field of mostly unfossilferous boulders.

Kirk attempting to crack a concretion the old fashioned way.

We left, hoping that a trip to Moloch beach would prove to yield some better vertebrate material. Moloch beach has an extensive exposure of the early middle Miocene Astoria Formation – which yielded one of the earliest discovered fossil marine mammals from the west coast – Desmatophoca oregonensis, an earlier relative of the large sea-lion like phocoid Allodesmus kernensis. Later, Remington Kellogg and Earl Packard described a new type of baleen whale from Moloch beach, which they named Cophocetus oregonensis. Later, several new pinnipeds were described from the Astoria Formation by Larry Barnes and colleagues: Pteronarctos goedertae, Pteronarctos piersoni, Pacificotaria hadromma, and Proneotherium repenningi; all of these, except P. goedertae, were found at Moloch beach. Subsequently, two more fossil pinnipeds were described from the Astoria Formation: Enaliarctos emlongi (possibly from the Nye Mudstone – near the Nye/Astoria contact) and the tiny phocoid Pinnarctidion rayi. These two were from a separate locality – where the bizarre “oyster bear” Kolponomos newportensis was discovered (…also by Emlong). Oddly enough, Enaliarctos emlongi is one of only two pinnipeds from that locality that don’t begin with P.

Some beautiful bivalves from the Astoria Formation.

We found a few chunks of rolled bone fragments – but nothing really interesting. Fossil localities with marine mammals are usually pretty easy to prospect – because whales are freaking huge, and have huge bones. It’s usually not hard to find vertebrae and ribs of baleen whales, and again, I was struck by how rare vertebrate remains were. Sure, there were some nice mollusks – but compared to fossil localities in California, like the Purisima Formation at Capitola where there are tons of beautiful mollusks littering the beach – the Astoria at Moloch beach was sort of average in terms of the number of invertebrates. After an hour or two of searching, I finally spotted a huge bone – the first in situ specimen at the locality. It was a large (~1.5 meter long) mandible of a baleen whale, perhaps something like Cophocetus. It’s technically legal to collect concretions from the Oregon coast with vertebrate remains in them – but not to dig bones out from the cliffs or wave cut bench. None of this detracts from Emlong’s legacy – in fact, the inability of three vertebrate paleontologists and several amateurs to find much of anything at any locality after a day of winter field work only makes his discoveries more amazing. My suspicion – and Kirk Johnson’s – is that Emlong capitalized on the fact that concretions sit around for a long time, and nobody before him collected vertebrate bearing concretions in such a systematic manner. There must have been concretions which had accumulated on the beach for thousands of years, and Emlong and subsequent collectors have effectively collected most of that ‘lag’ of concretions, leaving little for current visitors.

Ray sketching Kent Gibson's billfish.

After leaving the beach, we visited the nearby home of local amateur fossil collector Kent Gibson, who had found a partial billfish skull in a concretion at Moloch beach (possibly from the Nye Mudstone). It’s some sort of a huge Aglyptorhynchus-like billfish. Kent had an impressive collection, including a beautiful little pinniped skull that could be fairly important, if it were prepared and placed within a museum collection. Ray – being a fish guy – was wanting to see the billfish and other specimens. Upon arriving at Kent’s house, we saw a yard littered with fossils. Ray borrowed some sidewalk chalk from Kent’s kids and started drawing an outline of the billfish’s body as it would have appeared in life, to scale, with the fossil in place. Altogether it was pretty neat. But, we were getting hungry and Frank Boyden had invited us to dinner at his awesome cabin, decorated with his artwork and the artwork of others. Frank showed us some parts of his collection, including original prints by late 19^th century French ‘bohemian’ artist Odilon Redon. At one point, Frank needed to install a railing in his house – instead of installing any old railing, he went to the beach, got a stalk of bull kelp, and casted in bronze – and it is one of the coolest damn things I’ve ever seen. Frank showed us his printmaking studio, which was spectacular, and useful for me as an artist to learn about more involved artistic methods – pencil and paper is my bag, because it’s simple and primitive (and dirt cheap).

Frank's "cell phone"

We never got a break, even during dinner: Frank had all sorts of bits of animal skeletons. Here kirk and I puzzle over a large fish skull.

Yum!

I don't remember what was going on here.

Next up: behind the scenes at the Oregon coast aquarium, Sea Lion Caves, and the conclusion of the trip

Oregon coast trip with Ray Troll and Kirk Johnson, part 1: Lincoln city, Emlong's demise, Sitka Center

2013-03-03T16:12:00.002-07:00

A little while ago I realized that I had totally forgotten to talk about our trip to Oregon with Kirk Johnson and Ray Troll last February. I can’t believe it’s been a year already; after our trip to Oregon, my wife and I only had two weeks to finish packing for our three year trip to New Zealand, so I know exactly why I neglected to post about this earlier. Kirk and Ray are working on a new book project, sort of a sequel to “Cruisin the Fossil Freeway”, which was a combination of science, humor, Ray’s awesome art, and the tale of a huge road trip across the American west. This new project changes the focus from the western interior to the Pacific coast of North America – the new book project is titled “Cruisin the Eternal Coastline”, and deals with fossils from Baja California to Barrow, Alaska. Kirk and Ray received a Guggenheim fellowship in 2011 to begin leg work for the project. I first met the dynamic duo in October 2011, literally the day after I found out I had been accepted into the Geology Ph.D. program here at Otago. I showed the guys some of the fossils from my collection, which at the time I was still studying and curating (and are now all in UCMP collections). The next day, we visited a bunch of fossil localities in Santa Cruz, and visited a large mural by Ray at the Long Marine Lab in Santa Cruz.

Ray and Kirk got into contact with me because of my interest in west coast fossil vertebrates – specifically marine vertebrates. Granted, there are all sorts of spectacular land mammal localities as well (and even non-Cenozoic localities, but I won’t dare talk about those…), but the eastern North Pacific margin is home to one of the most extensively sampled marine vertebrate assemblages on earth. The majority of this record is from the coasts of California and Oregon. Ray and Kirk sent me an invitation to join them in coastal Oregon, to track down some of the haunts and old localities of one of my biggest paleontological heroes – Doug Emlong. The guys were even able to cover our travel expenses with their fellowship! Sarah and I left San Francisco, and headed up I-5 and reached Grant’s Pass by midnight. We left early the next morning, having to make it to the Overlook Motel in Lincoln City by 1pm. We just barely had time to take a short detour off Highway 20 to head south to Toledo to visit the type locality of Simocetus rayi, which was described by Ewan Fordyce (my Ph.D. adviser) in 2002. We followed the locality description by my advisor – which is effectively the same as Emlong’s notes. I’m not sure what has happened in the area, but there weren’t any cliffs or exposures of the Alsea Formation anywhere within a mile or two of the indicated point. It’s possible that exposures along the river are now overgrown – as I’ve seen with all sorts of localities in Humboldt County, California.

The type locality of Simocetus rayi - or, somewhere nearby it. Emlong's notes weren't always accurate, and there don't really appear to be any fossiliferous outcrops in the vicinity. Or, any outcrops at all. If there once were cliffs here, they have long since grown over with vegetation.

We finally made it to the motel with ten minutes to spare, just in time for Ray and Kirk’s talk on “Cruisin the Fossil Freeway”. They go on book tours, and have a ~40 minute presentation version of the book – and it’s a real hoot. I had seen it previously at the Bone Room in Berkeley during their bay area leg of the trip in October 2011; it was great, except for the fact that a member of the audience who knew a bit about fossils muttered to themselves and nodded agreement or verbally confirmed everything that came out of Ray or Kirk’s mouths – which was a bit irritating. The attendance at their talk in Lincoln City, however, was enormous – well over a hundred (maybe even two hundred) people showed up, which was phenomenal (both speakers were impressed with the turnout). After the talk, we met all sorts of locals interested in fossils, rocks, and paleontology – and spent at least another hour chatting with folks before leaving the motel. We met several local private collectors, as well as some members of the fossil club “NARG”, who I had heard about for years – they have the oddly non-specific title “North American Research Group”, but they are a seriously organized group of amateurs who are actually able to acquire permits from the state of Oregon to collect, prepare, and curate fossils into various permanent collections. And they do it all as volunteer work; several years ago, they collected a huge balaenopterid mysticete skull from the Empire Formation of Oregon; it’s still under preparation.

I also got to meet the esteemed Frank Boyden of the Sitka Center for Art and Ecology, north of Lincoln City; the center was established in 1970 by Frank and his wife Jane as a residency program for artists, scholars, and academics, with a humble beginning as a summer camp. Upon arriving at the motel, I learned that the talk was being sponsored by the Sitka Center. Frank is a fascinating person to talk to – warm, eccentric, talented, hospitable, and a total luddite. I knew we had some sort of accommodation, but this was one of those things that I had barely planned: Sarah and I were busy as hell with preparations for the move to the southern hemisphere, and Ray and Kirk had told me that everything was taken care of. I guess I was expecting a hotel room somewhere. What I didn’t realize was that Frank was graciously putting us up in some of the cabins at the Sitka Center – Kirk and Ray had their own, and Sarah and I had another. It was a wonderful surprise, totally out of left field. They’re these incredible “sea ranch style” cabins in the Oregon rainforest (sea ranch architecture will be familiar to anyone who’s spent any time on the central or northern California coastline, especially along Highway 1 in Sonoma and Marin Counties). I remember asking Ray whether or not we’d have wireless internet, and Ray reminded me that “Frank has a rock with painted buttons on it for a cell phone.” That was a good enough answer, I suppose. I should have remembered, because earlier at the talk I remember somebody asking him about a cell phone number and he gleefully pulled out his rock "phone".

Inside view of our incredible sea ranch style cabin in the Oregon rainforest at the Sitka Center.

To finish our first day of the trip, we tracked down the place where Douglas Emlong died. Using the police report deposited within the Emlong archive at the USNM, we tracked down the exact spot to a small ledge off the side of the road on the Otter Crest Loop between Depoe Bay and Newport, Oregon, just a few hundred yards north of the overlook parking lot. Emlong was a troubled person, and clearly suffered from some psychological issues. There is evidence of obsessive-compulsive disorder, or perhaps bipolar disorder – I’ve had many friends suffering from either, but Emlong’s case seems to have been more severe. He tended to quickly spend money he received from the Smithsonian, and in correspondence with Clayton Ray, he reacted rather extremely after learning that the Smithsonian was unable to appropriate enough funding to continue paying him (sometime around 1977-1978). In June 1980, Emlong returned empty handed from a trip to southern California, and after being back in Newport for less than 24 hours, leapt to his death off a cliff adjacent to the Otter Crest Loop. We only thought it fitting to make a pilgrimage to where the troubled genius met his end.

Douglas Emlong's last view. Not a bad one, in my opinion.

Ray, Kirk, and others reflecting on where Douglas Emlong met his end.

My wife looking down the cliff - it's about a five hundred foot plunge to the Pacific below.

Next up: A visit to the Yaquina Formation

Was Pelagiarctos a "killer" walrus? Part 5: life restoration

2013-02-12T05:39:00.003-07:00

Now that I’ve published research that made the front page of the fox news website, I can consider myself satisfied as a scientist. The Pelagiarctos article has made some additional press, including Science World Report, the Orange County Register, the Otago Daily Times (our local newspaper), and my favorite popular article, titled "Ancient "killer walrus" cuter than originally thought." Also, take a look at Brian Switek's write up on Laelaps.

It's in there, in between the articles about the second amendment and how the government

will be coming after you.

I thought I’d go ahead and explain in a post about the making of the life restoration of Pelagiarctos, and discuss what it may have looked like in life. As detailed in our phylogenetic analysis, Pelagiarctos is most closely related to the late Miocene walrus Imagotaria downsi. Imagotaria downsi is known from the Santa Margarita Sandstone and Sisquoc Formation of Northern and southern California (respectively), and is early late Miocene in age (Tortonian stage – 9-12 Ma). The type specimen of Imagotaria downsi is sort of a cruddy specimen, but a beautiful collection of well preserved fossils was reported by Charles Repenning and Richard Tedford in 1977 from the Santa Margarita Sandstone near Santa Cruz, California. Two skulls including an adult female (“Rep’s Girl” as some marine mammal paleontologists call it) and a subadult male are sea lion like in their morphology. They have long snouts, the skulls are flat-topped, and have low saggittal crests, large canines, and deep mandibles. Although superficially sea lion-like in general form, they lack the supraorbital shelves typical of otariids.

The female skull of Imagotaria downsi from Santa Cruz, affectionately known as "Rep's girl".

The lack of similarity between Pelagiarctos and the modern walrus is evident in its morphology. In the modern walrus, the canines are reduced in size to small pegs, no larger than the premolars (and are thus called ‘premolariform’); the incisors are totally absent, and the “chin” of the modern walrus mandible tapers to a triangular point that lacks teeth and instead has a longitudinal furrow. The transverse tapering of the mandible accommodes the hugely expanded tusks, which for the uninitiated, are the upper canines. The reduction in size of the lower canines presumably also permits enlarged upper tusks – while the complete loss of incisors probably allows an unobstructed pathway for suction into the oral cavity (see the section on odobenid dental and mandibular evolution in Odobenidae in our paper).

Rough line drawing of "Rep's girl".

Instead, Pelagiarctos – like Imagotaria – appears to be rather sea lion-like in overall morphology, perhaps something similar to one of the larger, more robust sea lions such as the New Zealand sea lion (Phocarctos hookeri), South American sea lion (Otaria byronia), or Steller’s sea lion (Eumetopias jubatus); the mandible of California sea lions is noticeably smaller and less ‘deep’ than Pelagiarctos. So, we have an overall idea of the shape of the head of Pelagiarctos. To start, I took a line drawing of the skull and mandible of Imagotaria downsi, and in adobe illustrator reduced them to the same mandible size. Then, I took the facial part of the skull, and shortened it to fit the short toothrow of Pelagiarctos. Figuring that the rostrum of Pelagiarctos would have probably been deeper and more robust like the mandible, I also made the facial region more dorsoventrally deep.

Cranial reconstruction of Pelagiarctos sp. based on the proportions of Imagotaria downsi.

Then, using this new skull reconstruction, I sketched it in an oblique view by using a reference photo of an Imagotaria skull in the same oblique view, while adding in the changes in proportions. I made sure to sketch it in an angle where I had a photograph of the new Pelagiarctos specimen, so that I could later on digitally overlay the photo of the mandible.

What did Pelagiarctos look like? More like a sea lion, or a fellow walrus? Due to its early position and early timing in pinniped evolution, it probably had some sort of external ears. It was not a gigantic cold-adapted pinniped like the walrus, so it may have primitively retained abundant fur or hair. It's long whiskers as I've reconstructed it are consistent with a piscivorous habit, rather than the molluskivorous feeding behavior of the modern walrus. My initial black and white graphite drawing is shown here.

So, we’ve got a general shape of the skull and head – but what would it look like? There are still a couple more considerations. For example – would it have had fur? Long vibrissae (whiskers), or short vibrissae? Would it have had thick blubber instead, like the modern walrus? And what about ears – modern walruses (and true seals) don’t have external ears, but sea lions and fur seals (Otariidae) have dinky little ear flaps. Before I continue with this discussion, I must stress that this is all highly speculative. Using the “extant phylogenetic bracket”, and assuming that molecular analyses have correctly identified sea lions and walruses as sister taxa, we can infer that it would look closest to a sea lion or a modern walrus. Okay, that basically includes all of the aforementioned features. The modern walrus is technically closer – but it is a highly derived animal, whereas Pelagiarctos is a very generalized sea lion-like pinniped. I reconstructed Pelagiarctos with external ear flaps to reflect the fact that most early pinnipeds probably had ear flaps or even large external ears (e.g. like an otter). After all, external ears are primitive, and it would be silly to assume that true seals and walruses have lacked ears throughout their evolutionary history. Considering the molecular support for a sea lion + walrus clade, it appears that external ear loss is convergent in the walrus and true seals anyway. What about fur, then? Only a few pinnipeds truly lack dense fur or hair – the walrus, and the elephant seals. The southern elephant seal and the walrus are both high latitude, cold water adapted - but they are also substantially larger than Pelagiarctos. Given the temperate latitude and similarity in size of Pelagiarctos with modern sea lions, which lack fur but have dense hair – it can be parsimoniously reconstructed as “fuzzy”. On that note, I really ought to talk about Heather Liwanag's awesome study on the evolution of marine carnivore fur/hair. Lastly, I reconstructed it with long whiskers because it’s a pelagic hunter – the short, stubby whiskers of the modern walrus are an adaptation for “feeling” benthic invertebrates and sediment.

And the final reconstruction, all colorized and everything. I had a lot of fun doing this reconstruction, and it seemed to do the trick.

Anyway, this concludes my series of posts on the new study by Morgan and I. Hope you enjoyed reading it (and hopefully the actual paper as well).

References-

Boessenecker, R.W. and M. Churchill. 2013. A reevaluation of the morphology, paleoecology, and phylogenetic relationships of the enigmatic walrus Pelagiarctos. PLoS One 8(1) e54311. doi:10.1371/journal.pone.0054311.

Epic fossil whale collage

2013-02-10T03:42:00.004-07:00

I walked into my labmate Cheng-Hsiu Tsai's office recently and saw that he had a new desktop background - there were some specimens I didn't even recognize. It's a collage he made with nearly every published fossil mysticete he could find (and some modern mysticetes). Tsai, who is currently on a two month research trip to Taiwan, Japan, and Australia - said it would be OK for me to share it here with you all - so, enjoy!

Was Pelagiarctos a "killer" walrus? Part 4: No, probably not. The feeding ecology of Pelagiarctos reassessed

2013-02-07T16:42:00.002-07:00

Sorry for the short break – I’ve been fairly busy the last two weeks doing a number of things, but most of all revising a manuscript that was accepted last week on barnacle-encrusted sea lion bones from Oregon. I’m also pleasantly satisfied with additional press attention our Pelagiarctos article got over the last couple of weeks, and the PLOS metrics indicates it’s already gotten 3,000 views, which is quite a few more than my 2011 fur seal article (under 100), although that’s probably because it’s 1) linked to in all the news articles and 2) not paywalled.

Comparison of the holotype (B, C) and referred mandible (A) of Pelagiarctos. From Boessenecker and Churchill (2013).

When Morgan and I started our research on the new specimen of Pelagiarctos, we realized that the most interesting application of the research would be reevaluating the interesting hypothesis by Barnes (1988) that Pelagiarctos thomasi was a specialized macrophagous predator. To recap, Barnes interpreted this novel hypothesis based on several lines of evidence: 1) Pelagiarctos thomasi is relatively rare in the Sharktooth Hill Bonebed relative to other pinnipeds (apex predators are rare because they require a large population of prey items to subsist upon), 2) sharp postcanine teeth roughly similar in morphology to those of bone-cracking hyaenids and borophagine canids, 3) a fused mandibular symphysis, suggesting an adaptation towards high bite force, and 4) large body size. In addition to these interpretations, Barnes (1988) further interpreted all the isolated teeth as being from males – as the holotype “chin” has large canines, and at least one of the postcanine teeth slipped right in to the empty alveolus of the holotype. The rest of the postcanines are of similar size, suggesting to Barnes that they were all from one gender. Most pinnipeds – and all fossil walruses for which we have sufficient sample sizes (even wee little Proneotherium) are sexually dimorphic, with larger males. Furthermore, one of the holotype canines was broken in life and then worn from continued use, which Barnes (1988) interpreted as the result of male-male combat. Barnes further speculated that the lack of females could be caused by geographic separation of sexes – certainly an intriguing possibility, but difficult to test with such a small sample size.

An example of a vagrant pinniped: a leopard seal that wound up on a New Zealand beach. Apparently this happens somewhat often, but regardless - New Zealand is not in the normal range of this animal. From keaphotography.org

We identified several other hypotheses which could just as parsimoniously explain the rarity of Pelagiarctos within the Sharktooth Hill Bonebed. Given the extremely large sample size of fossil vertebrates from the bonebed, and a century of intensive collecting, the rarity is probably a real phenomenon and thus probably not a result of preservational bias (least of which because Pelagiarctos is a large animal and has a higher preservation potential than the smaller but numerically more abundant Neotherium). Numerous studies of modern pinnipeds have demonstrated that they are prone to vagrancy – in the ocean, after all, it’s easy to get caught up in currents or forage further away than other members of your species. It’s also possible that Pelagiarctos was simply a pelagic, offshore pinniped, rarely straying into coastal waters off Orange County (“Topanga” Formation) or the Temblor Sea (Sharktooth Hill). Furthermore, the Sharktooth Hill Bonebed was deposited over a protracted period of time (~700,000 years) due to a depositional hiatus, and it’s possible that a short period of time could have seen introduction of Pelagiarctos (from further south, north, or further out in the Pacific) along with a brief change in climate, ecology, or circulation.

A sea lion and a fishy smorgasbord. Photo by David Doubilet.

The fused mandibular symphysis is a bit more ambiguous. The only modern pinniped with a fused symphysis is the extant walrus Odobenus rosmarus, and it’s not immediately clear why, or how it could be adaptive relative to feeding. My hunch is that it’s a secondary consequence of having a pachyosteosclerotic mandible – the lower jaw of Odobenus is thickened around the chin and dense, and development of this may have resulted in symphyseal fusion. The earlier walrus Alachtherium/Ontocetus has an unthickened chin and lacks fusion – but Valenictus chulavistensis (the strange sister taxon of Odobenus) has a fused symphysis, and also lacks a thickened “chin”. Extreme pachyosteosclerosis of the skull and mandible in Odobenus has been suggested as a possible adaptation for keeping the head negatively buoyant during benthic foraging. One other fossil odobenid has a fused symphysis – Dusignathus seftoni from the San Diego Formation. It’s not even clear what Dusignathus ate, so it’s not a very good analogue either. Barnes (1988) argued that a fused symphysis in Pelagiarctos thomasi suggested and adaptation for large bite forces – however, carnivorans with high bite forces such as borophagine canids and hyaenids (which Barnes compared the dentition of Pelagiarctos to), as well as sea otters – all have unfused symphyses, possibly to allow slight movement of the mandibles so as to avoid tooth damage (Scapino, 1981). So what was mandibular fusion in Pelagiarctos thomasi for? Who knows! That’s for someone else to figure out. Besides, the new specimen didn’t have a fused symphysis anyway.

Comparison of calculated trophic level and body mass in pinnipeds. Lower trophic level corresponds to feeding upon benthic invertebrates, and high trophic level corresponds to eating large fish and cephalopods. From Boessenecker and Churchill (2013).

A walrus after a successful seal kill. These events have only been witnessed a few times by humans. Apparently, walruses will use their powerful suction normally reserved for mollusks to literally suck the meat right from the bones. From moblog.net.

Another gory shot of a walrus feeding on a poor seal. From Vlasman and Campbell, Diseases and Parasites of Mammals of the Eastern Arctic.

We reinvestigated the issue of body size as well. Morgan has been working on a method to estimate the body mass of fossil pinnipeds, and his preliminary results indicated that the length of the lower toothrow is the single best predictor of body mass in a dataset of modern pinnipeds (fortunate for us, since all we had was a mandible to work with). Morgan was able to estimate the body mass of Pelagiarctos sp. at approximately 350 kg (~770 lbs), which is similar to some modern sea lions (male South American sea lions, California sea lions). There are much larger sea lions, however – the Steller’s sea lion (Eumetopias jubatus), which weigh up to 1,150 kg (2,500 lbs). Steller’s sea lion is the fourth largest pinniped (after the two elephant seals and the modern walrus), but is not a macrophagous predator: it feeds predominantly on fish, although it will occasionally prey upon juvenile pinnipeds. The modern walrus also occasionally preys upon juvenile seals and marine birds – yet it is clearly adapted and specialized for mollusk predation. All large bodied otariids predominantly eat fish as well, and many adult male sea lions of other species as well will also occasionally consume warm blooded prey when given the opportunity. Morgan further investigated this by calculating the trophic level of modern pinnipeds and plotting it relative to body mass. The result is that there is no apparent trend between body mass and diet – with one exception: the largest pinnipeds fed both at the high and low trophic levels (e.g. fish, cephalopods, as well as benthic invertebrates – e.g. walruses and bearded seals). In other words, large body mass doesn’t necessarily indicate anything specific about feeding ecology or diet. A previous analysis by Peter Adam and Annalisa Berta (2002) only found a very poor correlation between morphology and diet. That evidence of adaptations for macrophagy is lacking within pinnipeds is highlighted by the leopard seal: it does not use its postcanine teeth to feed upon penguins and seals, and only uses them for filter feeding for krill the rest of the year (8 months or so out of the year). When it feeds upon large bodied prey, it nips with its incisors and canines – which are not really any different from those of fish-eating pinnipeds. In other words, the only modern pinniped which could be argued to be a macrophagous apex predator only has dental specializations for feeding upon krill.

Arguably the only macrophagous pinniped - the leopard seal spends most of the year eating krill, and doesn't use its delicate postcanine teeth for killing penguins and seals, and instead only for filter feeding. Figures from Hocking et al. (2013).

So, not a "killer" walrus after all, but still a pretty intimidating beast.

So what did Pelagiarctos feed on? Probably fish, cephalopods, the normal menu for large bodied pinnipeds. It very well probably did feed upon warm blooded prey – occasionally, anyway (again, like modern pinnipeds). We’re not arguing that Pelagiarctos did NOT eat warm blooded prey – rather, we’ve made the case that Pelagiarctos lacked any adaptations which would lend themselves to macrophagy. One last point of interest – within the Sharktooth Hill Bonebed, Pelagiarctos is not even the largest pinniped; it’s dwarfed by Allodesmus, which Morgan estimated at 1400 kg (~3,000 lbs)! That’s just enormous (and approximately ¾ the size of modern northern elephant seals). Allodesmus, on the other hand, had enormous orbits possibly indicating deep diving adaptations (to which its large body size may have helped with as well), and a long snout with simple teeth – a definite contrast to the short “bulldog” face and dentition of Pelagiarctos.

References:

Adam PJ, Berta A (2002) Evolution of prey capture strategies and diet in the Pinnipedimorpha (Mammalia, Carnivora). Oryctos 4: 83–107.

Barnes LG (1988) A new fossil pinniped (Mammalia: Otariidae) from the middle Miocene Sharktooth Hill Bonebed, California. Contributions in Science, Natural History Museum of Los Angeles County 396: 1–11.

Boessenecker RW, Churchill M (2013) A Reevaluation of the Morphology, Paleoecology, and Phylogenetic Relationships of the Enigmatic Walrus Pelagiarctos. PLoS ONE 8(1): e54311. doi:10.1371/journal.pone.0054311

Hocking, D.P., Evans, A. R., and E.M.G. Fitzgerald. 2013. Leopard seals (Hydrurga leptonyx) use suction and filter feeding when hunting prey underwater. Polar Biology 36:2:211-222.

Scapino R (1981) Morphological investigations into functions of the jaw symphysis in carnivorans. Journal of Morphology 167: 339–375

Was Pelagiarctos a "killer" walrus? Part 3: new specimen from Orange County

2013-01-21T00:35:00.000-07:00

In early spring 2011, just as I was finishing up my master’s degree at Montana State, I received an email from Tom Deméré, the paleontology curator of the San Diego Natural History Museum, inviting Morgan and I to study a new fossil of Pelagiarctos from the “Topanga” Formation. Fortunately, I would get a chance to examine it closely in person soon afterward – in June, I would be attending and presenting my master’s taphonomy research at the 6^th triennial conference on secondary adaptations of tetrapods to life in the water (usually abbreviated SATLW or simply referred to as the aquatic tetrapods conference), which was being hosted by Tom Deméré and Annalisa Berta at San Diego State University and the museum.

Although I had successfully delivered my master’s defense presentation and graduated without a hitch a month and a half prior, I was still nervous to give my presentation because it was in front of a totally different audience – technically, the conference was about secondary adaptations, and I was giving a talk on taphonomy. However, I tooled it towards what we can reasonably infer from the marine vertebrate fossil record, including about exactly how aquatic organisms were based on their preservation – which, I concluded at the time was not much. The talk was also fairly long; although I had 18 minutes to speak, which is fairly long, I had not had the time to shorten it. 36 hours before driving down I-5, I was on the beach at Bolinas prospecting with Dick Hilton when I got a funny phone message from Tom ‘asking’ me if it would be okay to move my talk to the first day; so I said my goodbyes to Dick and raced home down Highway 1 so I could spend a day and a half polishing the presentation off. And then worried half the drive down I-5 that I didn’t shorten it enough.

A comparison of the new Topanga Formation specimen (A) and the holotype (B) of Pelagiarctos.

The talk went without a hitch, and later in the conference Morgan and I were able to sequester a few hours in the SDNHM type room to examine the new specimen of Pelagiarctos. It consisted of a fragmentary pair of mandibles, with the left mandible being nearly complete and having much of its dentition (missing only a premolar, the two molars, and an incisor). Unlike the type specimen from Sharktooth Hill (which Morgan and I got a chance to examine in person at LACM in January 2012), these mandibles were not fused together at the symphysis (intermandibular joint). Symphyseal fusion is not common in modern pinnipeds, where it is restricted to the modern walrus. I’ve also seen pathologic (diseased) mandibles of modern otariids where, due to some bone disease, the symphysis has fused along with a large mass of bone at the chin, accompanied by incisor and canine loss.

The left mandible of the Topanga Formation specimen of Pelagiarctos. From Boessenecker and Churchill (2013).

The teeth present in the new specimen confirm that the large teeth referred to Pelagiarctos thomasi by Barnes (1988) were correctly referred. It’s not so surprising, since you could predict the mandible shape from the teeth: they are like giant versions of Neotherium teeth, and the mandible is like a giant Neotherium jaw. I never really doubted Barnes’ identifications – but it was nice to confirm them. The mandible of this new specimen is damned huge – it’s wide, deep, with a short toothrow. The canines are robust, again with grooves on the lateral and medial surfaces, giving the canine a figure-eight shape in cross section. The premolars are large, primitively retaining what’s called the metaconid cusp; most modern pinnipeds have teeth that are unicuspid (single cusp, usually conical), with small anterior and posterior accessory cusps in otariids. The main cusp (on lower postcanine teeth) is called the protoconid. The anterior and posterior cusps are the remnants of the paraconid (anterior) and hypoconid (posterior) cusps. The metaconid cusp is a fourth cusp which is present in many primitive pinnipeds, such as the early enaliarctines, as well as Proneotherium, Neotherium, and Pelagiarctos. The metaconid is located just behind the principal cusp (protoconid). Many modern phocids primitively retain all four cusps – the harbor seal is an excellent example. The crabeater seal additionally bears a number of extra “neomorphic” (=new or novel structure) cusps on the posterior tooth crowns, which are used for filter feeding.

The dentition of the Topanga Formation specimen. From Boessenecker and Churchill (2013).

More details of the dentition of the Topanga Formation Pelagiarctos, from Boessenecker and Churchill (2013); I had a fun time drawing the medial view of those teeth.

In addition to having these primitive features, a couple of new features not seen in earlier walruses are present: a lingual cingulum with small little “crenulations” forming a sawtooth type pattern, and the presence of a labial cingulum. A cingulum is a thickened ridge of enamel at the base of a tooth crown. Pelagiarctos is the only walrus with a labial (cheek side of the tooth) cingulum, and only one other walrus has a crenulated lingual (tongue side of the tooth) cingulum – the late Miocene walrus Imagotaria downsi. At this point the uninitiated reader might ask ‘what exactly makes this thing a walrus?’ The truth is, for the earliest known walruses, the only synapomorphies allowing identification as a member of the Odobenidae (walrus family) are skull features. Many of the features of the known specimens of Pelagiarctos appear in some sea lions – such as a mandible that is deepest near the canines. Although the fossils don’t have any specific features that are diagnostic at the family level – several features of the dentition are only found in early diverging “imagotariine” walruses. The Imagotariinae was a subfamily named by Ed Mitchell and used extensively in various papers by Barnes, but as pointed out by several studies over the past two decades it is a paraphyletic assemblage of primitive walruses. Nevertheless, it is a useful vernacular term; imagotariines are sea lion-like with primitive dentitions, and ranged in size from harbor seal size (Proneotherium) to elephant seal size (Pontolis magnus).

Comparison of walrus mandibles, including the Topanga Fm. Pelagiarctos specimen, Imagotaria downsi from the late Miocene Santa Margarita Sandstone of Santa Cruz County, Proneotherium repenningi from the early middle Miocene Astoria Formation of Lincoln County, Oregon, and Pontolis magnus from the late Miocene Empire Formation of Coos County, Oregon. From Boessenecker and Churchill (2013).

Because our new specimen was more complete than the holotype, we were able to include Pelagiarctos within a phylogenetic analysis for the first time. Previous analyses did not use many mandibular characters, so at first we constructed a matrix which focused on mandibular and dental characters, and only used pinniped species known by lower jaws (i.e. we didn’t include some species for which jaws were unknown). This meant we didn’t initially include the early walruses Prototaria and Pseudotaria from Japan. We originally did this because we felt we’d get more accurate results than if we included Pelagiarctos in an analysis where it couldn’t be coded for any cranial characters – it was a reasonable hunch at first. One of our reviewers suggested we use a more comprehensive dataset, so we merged our data set with that of Naoki Kohno’s (2006) analysis for his Pseudotaria muramotoi paper. We ended up with fantastic results, and better support for some of the relationships.

Cladograms from Deméré (1994), Kohno (2006), and our new study showing the varying position of Pontolis (underlined in red).

Most of the relationships in our analysis are consistent with previous studies like Deméré (1994), Deméré and Berta (2001), and Kohno (2006), with one exception. In Deméré (1994), Pontolis magnus grouped as a dusignathine walrus, and closely related to Dusignathus itself. In Kohno (2006), Pontolis instead formed a sister taxon relationship with Imagotaria. The Imagotaria-Pontolis clade is only one node below the dusignathines, so admittedly it is not a far distance. In our analysis, however, Pelagiarctos formed a sister taxon relationship with Imagotaria instead, based on two features: grooved canines, and a crenulated cingulum. Neither of these features are present in Pontolis. Instead, Pontolis plotted out as the last diverging “imagotariine” and the sister taxon to the dusignathine + odobenine clade – in other words, intermediate between the phylogenetic hypothesis of Deméré (1994) and Kohno (2006). It’s sort of a compromise between the two, in a way. Obviously, there are more cranial characters that need to be explored and new walruses to describe, so there is clearly further scope for a more comprehensive study of walrus phylogenetics, which is in the early planning stages.

Next up: the dramatic conclusion to this series on the new publication, focusing on the feeding ecology of Pelagiarctos, and the life restoration.

References:

Barnes LG (1988) A new fossil pinniped (Mammalia: Otariidae) from the middle
Miocene Sharktooth Hill Bonebed, California. Contributions in Science,
Natural History Museum of Los Angeles County 396: 1–11.

Deméré TA (1994) The family Odobenidae: a phylogenetic analysis of living and
fossil forms. In: Berta A, Deméré TA, editors. Contributions in Marine Mammal
Paleontology honoring Frank C Whitmore, Jr: Proceedings of the San Diego
Society of Natural History. 99–123.

Kohno N (2006) A new Miocene odobenid (Mammalia: Carnivora) from
Hokkaido, Japan, and its implications for odobenid phylogeny. Journal of
Vertebrate Paleontology 26: 411–421.

Was Pelagiarctos a "killer" walrus? part 2: new publication in PLOS

2013-01-21T00:34:00.003-07:00

Last thursday my new study which I collaborated with Morgan Churchill (University of Wyoming) on was published in PLOS One, regarding new fossil material of Pelagiarctos from the "Topanga" Formation of Orange County, California. There has been quite a bit of buzz about it, and it's gotten a surprising amount of media attention. To summarize it in one sentence - we describe the new material, reanalyze the paleoecological hypothesis of Barnes (1988), concluded it was not a specialized macrophagous predator, and conducted a phylogenetic analysis of the Odobenidae (walruses).

Brian Switek was kind enough to cover it on Laelaps, which you can see here. Also, there is an author spotlight on the PLOS EveryONE blog, viewable here.

Part of the new specimen of Pelagiarctos, which Tom Deméré (San Diego Natural History Museum) invited us to study.

Life restoration of Pelagiarctos, which I did last fall in my spare time. More on how I put this together at a later point.

This has been covered by a ton of news outlets, including the University of Otago news service, ScienceDaily, LiveScience, MSNBC, NBC, Huffington Post, Cosmos, Yahoo News, and even Fox News (perhaps a dubious honor...).

The full article can be viewed here at Plosone.org.

Boessenecker, R.W. and M. Churchill. 2013. A reevaluation of the morphology, paleoecology, and phylogenetic relationships of the enigmatic walrus Pelagiarctos. PLoS One 8(1) e54311. doi:10.1371/journal.pone.0054311.

And, the morphobank account is available here.

Was Pelagiarctos a “killer” walrus? Part 1: Sharktooth Hill Pinnipeds

2013-01-15T23:05:00.001-07:00

As a teaser for a forthcoming paper by Morgan Churchill and myself, I thought I’d introduce a (short) new series of posts (fewer than the last series, I promise). As the publication is not out quite yet, I thought I could at least give an introduction to the extinct “killer” walrus from the Sharktooth Hill Bonebed.

The Sharktooth Hill bonebed in Kern County, California is a widespread horizon within the Round Mountain Silt member of the Temblor Formation. It’s exposed near Bakersfield, California, and is middle Miocene in age. It’s approximately 10-50 cm thick, generally lacks calcareous invertebrate fossils, but is extraordinarily rich in teeth and bones of sharks, bony fish, birds, sea turtles, pinnipeds, dolphins, sperm whales, baleen whales, and occasionally sea cows, desmostylians, and terrestrial mammals. I visited Sharktooth Hill several times as a high school student, trying to find “local” vertebrate fossils – digging well through the night in the trenches with tiki torches and a headlamp. At many localities frequented by amateur fossil collectors, the bonebed is exposed on a hillside and a large linear scar follows the position of the bonebed, dug out by collectors removing overburden to get to the fossil layer. Amateur fossil collectors have done so much digging that a trench reminiscent of World War 1 battlefields encircles many hills in the region where the bonebed is exposed. Although some collectors will spend days at a time digging through overburden - admittedly backbreaking work - some decide to risk it and tunnel into the trench to get at the bonebed. Some collectors have paid for this tactic with their lives: on my first visit in 2002, a cross was placed at one of the localities where a collector had tunneled in about ten feet and was killed when the hillside slumped down onto him; it took the authorities several days to dig out his body. The rest of the Round Mountain Silt is mostly barren with respect to vertebrate fossils, not only explaining the attention given by collectors to the bonebed itself – but also suggesting a “unique” environment temporarily persisted in order to concentrate vertebrate remains. A number of strange biologic explanations have been offered, including red tides, extensive shark predation, and even a marine mammal calving ground. Several authors have quite rightly scrutinized these biologic explanations, and have suggested sedimentologic processes as a cause (Mitchell, 1966; Prothero et al., 2008; Pyenson et al., 2009). These studies have specifically suggested that a depositional hiatus (slowdown in the accumulation rate of sediment) permitted marine vertebrate remains to be concentrated on the seafloor. I have some minor taphonomic reservations, but those are best discussed another day.

One of the Sharktooth Hill localities, wife for scale.

According to Barnes (1976), the Sharktooth Hill bonebed is the most extensively studied and richest marine mammal locality in the eastern North Pacific; a faunal list compiled by amateur collectors can be viewed here, and it includes roughly 140 vertebrate taxa. Some of the species on the list are not yet described or published (“Neotherium ernsti”, for example) and other taxa are based on old identifications and may not be borne out in the long run (aff. Herpetocetus). Regardless of issues pertaining to the taxonomic identity of some fossil vertebrates, the ballpark number is probably accurate. It’s also fairly spectacular: I recently tallied up fossil vertebrates from the Purisima Formation, and there are roughly 70 taxa present – still impressive as hell, but not quite as gargantuan as Sharktooth Hill. Depending upon whose publication you look at, there are anywhere from seven (Barnes, 1972; Barnes and Hirota, 1995) to four pinnipeds present (Deméré et al., 2003). Papers by L.G. Barnes and colleagues list several desmatophocids, including Allodesmus gracilis, Allodesmus kelloggi, Allodesmus kernensis, Desmatophocine B, and Desmatophocine C in addition to the imagotariine walruses Neotherium mirum and Pelagiarctos thomasi. According to Deméré et al. (2003), only four taxa are present – Allodesmus kernensis (with A. kelloggi and A. gracilis subsumed as junior synonyms), an indeterminate desmatophocid (Desmatophocine B), and the two walruses. While it’s nowhere near as diverse as the cetacean assemblage from the same locality, it’s fairly comparable with other fossil pinniped assemblages from the eastern North Pacific.

The skeleton of Allodesmus kelloggi as exposed in the field. From Mitchell (1966).

In 1980, future chief preparator of the Los Angeles County Museum of Natural History (LACM) discovered a curious chunk of bone with teeth at Sharktooth Hill. Several years later, he brought it in to LACM and showed it to Dr. L. G. Barnes (colloquially known as ‘Larry’ within the field), and insisted that it was the piece of a snout of some extinct mammal – it even had two small holes which look like nostrils to the uninitiated. Barnes kindly pointed out that those were mental foramina on the “chin” end of a very large jawbone of a pinniped. Larry and Howell enthusiastically recalled this whole story for Morgan Churchill and I when we sat at the very same table last January, thirty or so years later (Larry Barnes has an incredible, near photographic and certainly encyclopedic memory of marine mammal fossil specimens). Howell Thomas donated the fossil for study, and within a few years was hired as the Chief Preparator, and Barnes began to study the specimen. At the time, the marine mammal assemblage was already enormous, and the pinniped assemblage well documented by hundreds of specimens. Most of the fossils could be assigned to the large seal-like Allodesmus, although a single jaw described by Barnes (1972) as “Desmatophocine B” didn’t appear to be referable. “Desmatophocine B” was probably similar to Allodesmus, which has a long narrow skull, enormous eye sockets, single-rooted teeth, and a relatively large body. Furthermore, we know Allodesmus retained the ability to rotate its hindflippers forward for sea-lion like terrestrial locomotion, and it was probably a sea-lion like underwater “flyer”. Numerous small pinniped elements appeared to be similar to a handful of elements described by Remington Kellogg (1931) as Neotherium mirum.

Skulls of Allodesmus (left) and Neotherium (right) roughly to scale. From

Barnes and Hirota (1995) and Kohno et al. (1995).

Neotherium was an enigma for over 60 years, and it wasn’t until more complete remains of the early walrus Imagotaria downsi were recovered from the Santa Margarita Sandstone near Santa Cruz, California, that Neotherium began to make sense. Imagotaria was a sea lion-like walrus that lived about 9-12 million years ago – a bit younger than the 15-16 Ma Sharktooth Hill Bonebed – and by the close of the 1970’s was known by a number of well preserved skulls and partial skeletons from Santa Cruz County. Fossils of Neotherium, although never as common as Allodesmus, continued to trickle in from the bonebed and were referred to Neotherium piecemeal, one or two bones at a time by Mitchell (1961), Mitchell and Tedford (1972) and Repenning and Tedford (1977). By the 1980’s, Barnes had amassed a collection of nearly every skeletal element of Neotherium, identifiable as miniature and slightly more primitive versions of that found in Imagotaria – including partial skulls and several mandibles (eventually a complete skull was published by Kohno et al. 1995). Barnes has been for many years working on a monograph on Neotherium – I’m looking forward to seeing it published.

The holotype of Pelagiarctos thomasi. From Barnes (1988).

Howell Thomas’ mystery jawbone appeared more similar to Neotherium relative to Allodesmus, with the exception of its comparably gigantic size as well as having a fused intermandibular joint (mandibular symphysis) and deep grooves on the sides of the canines. Eventually, several isolated teeth that were similar to Neotherium, but several times larger in size – were discovered from the bonebed. Some of these teeth even fit right in to the tooth sockets in the mandible fragment. Barnes published the fossils in 1988 and described them as Pelagiarctos thomasi, the species name honoring Howell Thomas. The genus name Pelagiarctos refers to the primitive dental anatomy, as ‘arctos’ refers to bears, the traditional sister taxon of pinnipeds (the root arctos is frequently used in pinniped genus names – Arctocephalus, Phocarctos, Hydrarctos, Pteronarctos, etc.), as well as the inferred pelagic ecology of the animal.

The isolated teeth referred to Pelagiarctos by Barnes (1988).

Several aspects of the anatomy of Pelagiarctos, although based on scant material, suggested a different approach to feeding in this fossil walrus relative to other Sharktooth Hill Pinnipeds. The teeth of Pelagiarctos were huge – very robust canines, and postcanine teeth with multiple large cusps and sharp crests. He likened the premolars and molars to those of modern hyenas and extinct borophagine dogs, two groups which (by observation or inference) crack and ingest bones, suggesting that Pelagiarctos had dental adaptations for large bite forces related to feeding on large prey items. Furthermore, the robust mandible and fused symphysis further suggested high bite forces. Barnes (1988) additionally noted that Pelagiarctos is very large and numerically rare in the Sharktooth Hill Bonebed – only known by five teeth and a mandible fragment at the time of his study, as opposed to the hundreds of specimens known of other pinnipeds such as Allodesmus and Neotherium. This suggested to Barnes that Pelagiarctos was rare in California waters during the middle Miocene, further supporting his hypothesis that it was an apex predator (apex predators at the top of the food chain can never be very abundant because they rely on a constant stock of abundant prey items). Barnes further postulated that the type specimen was a male, as it had proportionally large canines; modern and fossil pinnipeds are sexually dimorphic, including early walruses like Neotherium, Imagotaria, and Proneotherium. One of the canines in the holotype is broken and polished down, suggesting the tooth had been broken and worn down after continued use in life – damage which Barnes attributed to male combat, which occasionally results in such damage in modern pinnipeds. Furthermore, Barnes identified some of the fossil teeth as males because they fit right into tooth sockets on the type specimen, and those that didn't were of similar size.

As a result of these hypotheses, numerous fanciful reconstructions of Pelagiarctos have been produced by paleoartists (fanciful depictions can be seen here, here, and here). and Pelagiarctos has achieved the nickname "killer" walrus by some enthusiasts. But what do we really know about Pelagiarctos? Stay tuned...

References –

Barnes LG (1972) Miocene Desmatophocinae (Mammalia: Carnivora) from California.

University of California Publications in Geological Sciences 89: 1-69.

Barnes L.G., 1976, Outline of eastern Northeast Pacific fossil cetacean assemblages:

Systematic Zoology, v. 25, p. 321–343,

Barnes LG, Hirota K (1994) Miocene pinnipeds of the otariid subfamily Allodesminae in the North Pacific Ocean: Systematics and Relationships. The Island Arc 3: 329-360.

Deméré TA, Berta A, Adams P (2003) Pinnipedimorph evolutionary biogeography. Bulletin of the American Museum of Natural History 13: 32-76.

R. Kellogg. 1931. Pelagic mammals of the Temblor Formation of the Kern River region, California. Proceedings of the California Academy of Science 19(12):217-397

Kohno N, Barnes LG, Hirota K (1995) Miocene fossil pinnipeds of the genera Prototaria and Neotherium (Carnivora; Otariidae; Imagotarinae) in the North Pacific Ocean: evolution, relationships, and distribution. The Island Arc 3: 285-308.

E. D. Mitchell. 1961. A new walrus from the imperial Pliocene of Southern California: with notes on odobenid and otariid humeri. Los Angeles County Museum Contributions in Science 44:1-28

Mitchell ED (1966) The Miocene pinniped Allodesmus. University of California Publications in Geological Sciences 61: 1-46.

Mitchell ED, Tedford RH (1972) The Enaliarctinae: a new group of extinct aquatic Carnivora and a consideration of the origin of the Otariidae. Bulletin of the American Museum of Natural History 151: 203-284.

Repenning CA, Tedford RH (1977) Otarioid seals of the Neogene. Geological Survey

Professional Paper 992: 1-87.

D. R. Prothero, M. R. Liter, L. G. Barnes, X. Wang, E. Mitchell, S. McLeod, D. P. Whistler, R. H. Tedford, and C. Ray. 2008. Land mammals from the middle Miocene Sharktooth Hill Bonebed, Kern County, California. New Mexico Museum of Natural History and Science Bulletin 44:299-314

Pyenson ND, Irmis RB, Lipps JH, Barnes LG, Mitchell ED, et al. (2009) The origin of a

widespread marine bonebed deposited during the Middle Miocene Climatic Optimum.

Geology 37: 519-522.

Sinus anatomy of modern porpoises revealed by CT imaging

2013-01-14T03:48:00.002-07:00

Congratulations are in order to my colleague and friend Rachel Racicot, a Ph.D. student at Yale (working under Jacques Gauthier), for getting her master's research published in the Journal of Morphology. Rachel did her Master's at San Diego State with Annalisa Berta, and was just finishing up when I visited the San Diego NHM for the first time in 2007. Aside from functional morphology and the endocranial anatomy of odontocetes (particularly cranial sinuses, brain endocasts, and the inner ear), Rachel is also interested in fossil porpoises and is currently researching the strange "half-beaked" porpoise from the San Diego Formation. Rachel's master's research concerns the pterygoid sinus morphology of modern porpoises.

Ms. Racicot had no idea that the journal had selected her image to be put on the cover

of the January 13 issue, and she was quite surprised when I congratulated her on it. Pleasantly

surprised, I should say.

Before I continue, I should briefly introduce phocoenids. The Phocoenidae, or true porpoises, are a small bodied group of delphinoid cetaceans that are not terribly diverse (6 species, 3 genera) in comparison to oceanic dolphins (Delphinidae; ~40 species, ~12 genera). They differ from delphinids in having short rostra, having symmetrical skulls, large bumps on the premaxillae just before the bony nares, and have inflated braincases without large bony crests. Phocoenids are considered to be paedomorphic -that is, retaining juvenile features into adulthood, thus explaining A) their inflated, juvenile-like braincases, B) lack of strong bony crests, C) cranial symmetry, D) short rostra, and E) small body size. It should be noted that the delphinid Cephalorhynchus is thought to parallel phocoenid paedomorphosis. Modern phocoenids also have strange, spatulate teeth which almost resemble the teeth of nodosaurs and ankylosaurs. Many fossil phocoenids, on the other hand, have longer rostra, conical teeth, cranial asymmetry, and better developed cranial crests.

Schematic view of a neonatal harbor porpoise (Phocoena phocoena) skull showing in blue the various parts of the pterygoid sinus. From Racicot and Berta (2013).

The pterygoid sinus is present in all Neoceti, and even within basilosaurids. It originates as an outpocket of the eustachian tube (an air filled cavity present in the middle ear of all mammals - hold your nose with your fingers and blow, and you'll feel crackling in your eustachian tubes; they are also what "pop" when changing altitude as the pressure changes). Parts of the sinus system can be seen externally, such as the hamular lobe of the pterygoid sinus, which is not completely encased in bone and is visible in a prepared skull as large cavities surrounded by thin flanges of bone. The pterygoid sinus system is elaborated in odontocetes relative to mysticetes. Although known to exist, the anatomy of the pterygoid sinus system in odontocetes - and true porpoises (Phocoenidae) in particular - is difficult to assess. Since they are cavities within a solid object, it's difficult to study them by any conventional means as they remain hidden in the skull. Certain aspects of the pterygoid sinuses have, for example, been used in phylogenetics - in multiple phylogenetic analyses which have included phocoenids, a cladistic character has been used - presence or absence of a dorsal extension of the preorbital lobe of the pterygoid sinus between the maxilla and frontal bone (po on the above diagram). This is a phocoenid feature, and the bottlenose dolphin lacks this. The preorbital lobe is well developed in the neonatal specimen (neonate = newborn individual, rather than a juvenile or subadult), although the dorsal extension is not as well developed as in the adults (an example of ontogeny recapitulating phylogeny).

Digital 'endocast' of the right pterygoid sinus (in medial view) from six skulls of Phocoena phocoena; anterior is to the left. Neonate specimen shown in F. The sinus shape looks pretty weird (but then again, so does the rest of a cetacean skull). From Racicot and Berta (2013).

So, what's it for? Previous hypotheses for the function of the sinus includes A) an acoustic barrier to reflect sounds produced during echolocation forward through the melon, B) an acoustic barrier between sound producing and sound receiving structures (e.g. nasal region and petrotympanic complex, respectively), and C) to acoustically isolate the petrotympanic complex from sounds produced during echolocation (which, admittedly, sounds similar to B). A fourth hypothesis posits that the pterygoid sinus serves as a means to regulate pressure around the middle ear during diving.

The paired sinuses (right and left) of Phocoena phocoena specimens in anterior view. Note that there is right-left asymmetry in each specimen. From Racicot and Berta (2013).

To test the sound reflecting ability of the sinus, Racicot and Berta calculated the minimum thickness necessary to reflect sound at the typical highest frequency sounds produced by Phocoena phocoena (~150 kHz). Many aspects of the cetacean skull make sense in the light of acoustic impedence - sound waves tend to bounce off of objects or features where there is a stark change in density. For example, echoes in air are sound waves bouncing off a solid surface. In water where the medium is much denser, sound not only travels faster, but flesh and bone are so similar in density that sounds travel through the vertebrate body rather than bouncing off of it - making things like external ears (which take advantage of sound waves bouncing due to acoustic impedence, and funnels sound in) useless. So, within a skull, a wall of air within a sinus is different enough in density to reflect sound, analogous to a solid object in air.

They calculated that the preorbital lobe would need to be 2.5mm thick at a minimum, which is less than what they observed in phocoenid sinuses - indicating they would function well at reflecting sounds. As for the asymmetry of the sinuses, they remarked that this could be explained by the fact that experiments have determined that porpoises produce sounds in an asymmetric fashion, preferring to use one nasal passage over the other, potentially explaining why the sinuses are asymmetrical.

Wild speculation time: it's also possible that aysmmetrical sinuses may be a vestige of cranial asymmetry. Fossils show that the earliest phocoenids had asymmetrical skulls in a similar fashion to delphinids; perhaps this is an example of phylogenetic inertia - the external skull changed at a faster pace than the sinuses, reaching symmetry first. However, paedomorphosis typically progresses by delaying adult morphology later and later during ontogeny, and retaining juvenile features longer and longer instead. In other words, paedomorphosis would suggest that asymmetry was once an adult feature which at some point was lost because juvenile symmetry prevailed - which doesn't totally jive with asymmetrical sinuses being retained, unless the two are decoupled somehow, progressing along different ontogenetic trajectories. Or, is asymmetry so ingrained within odontocetes that it's a juvenile feature in phocoenids, with symmetry really being secondarily gained via hypermorphosis, with asymmetry being pushed earlier on in ontogeny? Interesting questions, but they remain unanswered. We need more fossils and further studies of modern phocoenid cranial anatomy.

Another last thought - it's interesting to note that phocoenids are considered paedomorphic, but have relatively extensive pterygoid sinuses. The primitive condition among Neoceti, of course, is possessing less well developed sinuses (pterygoid sinuses in Neoceti and Basilosauridae are acquired stepwise in a piecemeal fashion). In other words - sinus development is not showing a paedomorphic trend - in fact, it's showing the opposite trend - it's a peramorphic feature, probably undergoing something like hypermorphosis (development is postponed and extended later into ontogeny) or acceleration (faster development of a feature during ontogeny). Perhaps hypermorphosis is not likely, given the short period it takes for phocoenids to mature.

References:

Racicot, R.A., A. Berta. 2013. Comparative Morphology of Porpoise (Cetacea: Phocoenidae) Pterygoid Sinuses: Phylogenetic and Functional Implications. Journal of Morphology 274:49-62.

Fordyce lab featured in local news

2013-01-11T18:17:00.002-07:00

Perhaps it was a slow news day in Dunedin since there are no rascal scarfie students burning couches in the streets (it's summer break here, and relatively hot today), but we were interviewed and photographed for the Otago Daily Times yesterday. I don't have permission to include a copy of the photo here, but you can see it here on the Otago Daily Times webpage. Unfortunately fellow marine mammal students Cheng-Hsiu Tsai (currently conducting research in Japan) and Moyna Mueller weren't around.

Bone-eating zombie worms, part 4: more on bird bones, and Osedax colonizes whale teeth

2013-01-09T14:38:00.001-07:00

As covered in a previous post, Kiel and colleagues (2011) recently reported on Osedax traces in Oligocene marine bird bones (Plotopteridae) from Washington, implying that by the late Paleogene Osedax was adapted towards using bones of many types of marine vertebrates (birds and cetaceans). This has direct implications for the divergence time of Osedax - two dates have been determined by molecular divergence dating: Eocene (coinciding with the radiation of pelagic cetaceans), or Cretaceous (a period with numerous large marine reptiles). Kiel et al. indicated that medium sized birds spanned the K/Pg interval and were some of the only marine tetrapods with available bony substrate during certain areas in this time interval. Fish bone, of course, is always going to be more plentiful in the marine record - but fish bones are generally small, and at the time of publication, Rouse et al. (2011) had not yet published their experimental colonization of fish bones by Osedax. Later that year, Higgs et al. (2011) indicated that the bimodal size of boreholes and lack of distinct individual cavities could suggest that Kiel et al. (2011) had not really reported Osedax colonizing bone, but that the traces on bird bones may actually be sponge borings - sponges form a trace called Entobia, which looks (on typical substrate like mollusk shells) like a bunch of tiny pinholes; the sponge inhabits the cavity, using the numerous tiny pinholes for inhalent papillae, and a few larger pinholes for the exhalent papillae.* Additionally, the borehole density reported by Kiel et al. (2011) was far denser than reported on experimentally colonized whale bones, which Higgs et al. (2011) further identified as evidence that the Oligocene bird bones were not in fact Osedax-bored, but sponge-bored.

Close up shot of the bone surface, showing the two sizes of pinholes in the Oligocene plotopterid. Are they the sponge trace Entobia, or the Osedax trace Osspecus? From Kiel et al. (2011).

Steffen Kiel and colleagues followed up their previous discoveries with a new paper in Paläontologische Zeitschrift, reporting in more Oligocene marine vertebrates bored by Osedax: fish bones and whale teeth. Altogether, it's not all too surprising: we have borings in a wide array of modern and fossil critters already. We already have modern fish bones - the really cool thing, in my opinion, is that Osedax will consume teeth. At the moment, I'm wrapping up a large manuscript which does include a little blurb and a figure showing possible Osedax borings in a dusignathine walrus tooth - which means I've got to add a new reference to my paper. But that's a story for another day.

Osedax-bored fish bone, from the Oligocene Makah Formation of Washington state. From Kiel et al. (2012).

The fossils hail from various Oligocene deep water rock units which are already known to produce whale fall faunas, cold seep assemblages, and wood falls. These include the Makah and Lincoln Creek Formations of the northern coast of the Olympic peninsula, as well as the (also) Pysht Formation just across the river from beautiful Astoria, Oregon. Coauthor Jim Goedert and his wife Gail have prospected the rugged coastline of the Pacific Northwest for decades, finding marine mammals, sharks, and marine birds. He's described Paleogene pelagornithids from the area, and named a plotopterid (Phocavis). The toothed mysticete Chonecetus goedertorum from Washington was named for them (they collected the holotype in 1984), and Gail also found what would later become the holotype of Pteronarctos goedertae in Oregon.

Archaic mysticete teeth from the Oligocene Pysht Formation of Washington with Osedax borings. From Kiel et al. (2012).

Arguably the most surprising finding of Kiel et al's new study is the pervasive boring of whale teeth. These teeth were all found in a partial, highly corroded mandible; the authors did not specify what kind of corrosion, but it was in all likelihood bioerosion (and Osedax related at that). They didn't identify what kind of mysticete the teeth belonged to - published aetiocetids from the Oligocene of Oregon and Washington have simpler teeth, but I have seen aetiocetid teeth in USNM collections similar to these. In several specimens, the crown was heavily bioeroded by Osedax, and the root just below the crown was as well. They argued that the loss of the crown in some cases was caused by scavenging invertebrates (possibly crustaceans) accidentally damaging the root while trying to eat the Osedax worms. Similar crustacean-mediated destruction of bone has been observed in modern whale falls. (As a total aside, it's mid summer here in New Zealand, and both my wife and I got pinched on the toes by shore crabs while in the water.)

CT images of the Osedax borings within the whale teeth, with individual borings shown in yellow in 3D below. From Kiel et al. (2012).

Kiel et al. (2012) also took the opportunity to respond to some of the comments by Higgs and colleagues about the bird bone traces. Kiel et al. pointed out that in numerous modern specimens, they observed comparatively dense Osedax borehole clustering, so extreme borehole density does not invalidate the their identification. Kiel et al. (2012) also point out that there were mollusk shells present along with the bird bones, and the shells were not bored; shells are the typical substrate for such boring sponges. As a taphonomist, I should note that this argument doesn't necessarily hold sway: most marine assemblages are time averaged, and because vertebrate and mollusk remains are of different chemistry, size, and have different soft tissue anatomy and production rates, they are subjected to different taphonomic pathways. In other words, it is certainly possible that the period of modification was different for the bones and shells. To make that more clear: the whale fossil could have been sitting on the seafloor exposed for a long period of time, allowing Osedax to colonize; towards the end of the pause in sedimentation, some mollusk shells are washed in and buried too quickly for the shells to have also been colonized. Or, the mollusks could have been burrowing taxa. Back on topic: Kiel et al. (2012) concluded that these fossils demonstrate that Osedax has been a generalist bone-consumer for over thirty million years, which strikes another blow to the "Osedax as a cetacean bone specialist" hypothesis.

*I'm no expert on Poriferan anatomy, but I can only assume that the papillae are homologous to the large openings through which water is pumped in and out.

Don't forget to see the other posts in this series:

Bone-eating zombie worms, part 3: Osedax consume more than cetacean bones

Bone-eating zombie worms, part 2: the discovery of fossil Osedax traces

Bone-eating zombie worms, part 1: whale falls and taphonomy

References cited:

Higgs, N.D., C.T.S. Little, A.G. Glover, T.G. Dahlgren, C. R. Smith, and S. Dominici. 2011. Evidence of Osedax worm borings in Pliocene (~3 Ma) whale bone from the Mediterranean. Historical Biology 24:269-277.

Kiel, S., Kahl, W. A. and Goedert, J. L. 2010 Osedax borings in fossil marine bird bones. Naturwissenschaften 55:51–55.

Kiel, S., Kahl, W. A. and Goedert, J. L. 2012. Traces of the bone-eating annelid Osedax in Oligocene whale teeth and fish bones. Paläontologische Zeitschrift DOI 10.1007/s12542-012-0158-9

Rouse, G.W., Goffredi, S.K., Johnson, S.B., and R.C. Vrijenhoek. 2011. Not whale-fall specialists, Osedax worms also consume fishbones. Biology Letters 7:736-739.

US research trip, part 11: more photos from Charleston

2013-01-06T04:07:00.000-07:00

I realized that my photos from Charleston did not really include much in the way of candid photos, or photos of us (you know, people). My camera has a narrow field of view and is ill suited for getting 'action' photos. Fortunately, my colleague Tatsuro Ando has graciously allowed me to post some photos he took of the gang and exhibits while in Charleston. Thanks, Tatsuro!

Another view of King Street in Charleston.

Ewan and I enjoying some beer after a long drive from North Carolina. This was my first time eating real barbecue after starting my Ph.D. program, and damn was it good.

Ewan and I looking at the model of the Hunley outside the Charleston Museum.

The pier at Folly Beach, South Carolina - we ate dinner at a restaurant at the base of the pier.

The Sanders' treated us to dinner at a great seafood place in Folly Beach (south of downtown Charleston). I tried shrimp n' grits for the first time - it was delicious. From left to right, clockwise: Rhonda Sanders, Al Sanders, Ewan, Myself, and Eric Ekdale.

Al and Ewan on the Sanders' screened in porch, overlooking the South Carolina 'forest' (better termed jungle, in my opinion).

The view out into the forest; a few minutes later, a raccoon came climbing by. It was a welcome sight, although it is pretty neat seeing brushy tailed possums here in Dunedin.

After a wonderful seafood dinner, discussions of cetacean evolution, key lime pie, and genuine southern hospitality - and we were ready to take a cab back into town. (From left: Eric, yours truly, Rhonda, Al, and Ewan).

A skull of Schizodelphis from the Calvert Cliffs, on display at the College of Charleston.

A cacophony of mosasaurs on display at the College.

Ewan inspecting some Carcharocles megalodon teeth, unaware of how funny this ended up looking.

Basilosaurid teeth from South Carolina (College of Charleston).

Desmostylian teeth from the middle Miocene Temblor Formation of California (College of Charleston).

To examine fine details of mysticete palates, sometimes you have to get in pretty close.

Someone else (Ewan I suspect) snapped a pinup-esque picture of me doing this, which has hopefully

been deleted forever.

A mounted cast of Pteranodon at the College of Charleston.

A Platecarpus (mosasaur) skull and cervical vertebrae mounted at the College of Charleston.

The gang's all here: Tatsuro, myself, Ewan, Al, and Eric in Charleston Museum collections. Thanks, Al, for a great time (and good food!).

Thanks again to Tatsuro Ando for letting me post these photos.

US Research trip, part 12: SVP, the hurricane, and the future

2013-01-05T20:35:00.000-07:00

We're finally at the conclusion of this long set of posts about my month-long trip back to the US. I've sort of told it in sequence, with the exception of SVP, which was in the middle of the trip, and right before the trip down to Charleston. The SVP meeting was great - my 8th meeting, and the 6th at which I've presented research. I gave my second SVP talk this year - this time, I presented results of my master's thesis research on marine vertebrate fossils from the Purisima Formation near Santa Cruz, California.

I carried out my master's research from 2008-2011 at Montana State, and collected taphonomic data from fossil vertebrates I had collected, as well as specimens from UCMP and the Santa Cruz Museum of Natural History. We have a very poor concept of the taphonomy of marine vertebrates - and sought to clarify some of these issues by studying changes in preservation among different shallow marine depositional settings.

Title page from my SVP talk. The image is taken near Halfmoon Bay, with my wife

Sarah standing in for scale beside stacked beds of hummocky cross-stratified sandstone,

characteristic of the "middle shelf".

Most previous taphonomic studies of marine vertebrates have focused on single skeletons or bonebeds - which admittedly doesn't tell us much about the big picture. I'll spare you the details for now (least of all because it's not published yet), but the research addresses some of these big picture questions and patterns. The talk went off without a hitch, and I was able to meet with quite a few colleagues. The night before the talk, I did benefit from finding a jacuzzi with a few friends in a vain attempt to relax. I'd given the talk before, three other times - at my defense, at the aquatic tetrapods meeting, and again at Fossil Coffee at UCMP - but getting up in front of a huge audience at SVP is something else altogether. Unfortunately, because the talk was on the last day of the conference, the meeting flew by way too quickly - one of the reasons I enjoy poster presentations much more.

Another slide from my talk, showing examples of Purisima Formation marine vertebrates.

SVP is also a fantastic time because it's one of the few times you ever get to see old friends. Many friends of mine I had not seen since my wedding last year; it was a bit difficult waking up the day after SVP and not being able to go find mobs of familiar faces milling about in the hotel lobby. Nevertheless, there is always next SVP.

I'm currently nearing submission of the manuscript version of my master's thesis, something I've been looking forward to for a long time. I try to keep projects moving, and would rather not get too caught up and sit on them; it's only been a year and a half since I graduated and completed my master's, so I suppose I'm doing well. The manuscript has taken a lot of time to modify - I've spent almost as much (or even more) time editing it over the past 6 months than I did writing it in the first place, and it is a far better piece of writing because of it. With this, and the September submission of another monstrous manuscript (also 100+ pages), I've cleared off a sizeable part of my research backlog.

After SVP, and Charleston, I had another week in Washington D.C. I was scheduled to fly out to California on Halloween. I kept hearing things on the news while in Charleston about a hurricane, but didn't really think too much of it - after all, hurricanes only happen on the east coast, right? As a Californian, I've always sort of filtered out news like tornadoes and hurricanes. And then I remembered, like some sort of bizarre moment of existentialist realization - that I was in Washington D.C. of all places, with a gigantic hurricane heading more or less right for us, with landfall in about four or five days. Fortunately, I was staying in D.C. with my childhood friend (and aide for the Senate Committee on Veteran's Affairs) Ben Merkel - who lives in a brownstone north of downtown, on a sloped street far from any drainage, and separated from the street by about 15 feet of steps. I felt pretty safe. Unfortunately, it also meant that I'd have to miss two days of museum work. Well, shit happens, and I was able to come in over the weekend before Sandy hit. We spent the 48 hour period while the city was shut down watching movies, eating and cooking, and drinking a healthy amount of beer. We only lost power for half a second when the lights flickered - once. We had internet the whole time, and I was able to work on some peer reviews and writing up a short manuscript on Herpetocetus. It was actually a pretty fun and productive time. Best of all, I was even able to make it out to the Garber facility for a few hours on my last day in DC to get some much needed photos. The storm had largely bypassed DC - we had some pretty heavy rain and high winds, and they had to close down the DC metro and buses and sandbag a bunch of federal buildings, but all the damage we saw included a few newspaper stands blown into the street. And my flight even left on time!

All in all, the trip was a total success, and I was able to arm myself with all the data and photographs necessary to complete my thesis here in New Zealand. I even had enough time while on the trip to start and finish an entire manuscript (a short one, anyway).

US Research trip, part 10: College of Charleston

2013-01-03T19:14:00.001-07:00

At the welcome reception at the North Carolina Museum of Natural History, I spoke with my colleague and good friend Jonathan Geisler about a new collection of fossil cetaceans at the College of Charleston, being managed by Mace Brown, shown below. I was pretty excited about it after hearing Jonathan describe it; I was totally blown away when I saw it. The collection is already pretty fantastic, and upon my arrival at the college, I saw an entire table full of fossil treasures. The museum displays were also great. Thanks to Mace for a successful (if all too brief) visit!

Mace Brown with a new eomysticetid fossil, which J. Geisler has graciously invited me to study with him. This was a recent acquisition, and Mace was still gluing parts of the mandibles back together. What an awesome fossil!

I furiously scribbled down notes - I had two 3-hour periods where I was able to examine the fossils at the College of Charleston. A herpetocetine petrosal is shown.

Eric Ekdale (left), Ewan Fordyce (middle), and Tatsuro Ando (right) inspect fossil cetaceans.

Mace Brown and the eomysticetid.

Al Sanders (right) and Ewan discuss fossil cetaceans. This was the first time Ewan and Al had met face to face since the 2006 SVP meeting - its tough, New Zealand is pretty far from everything.

Some sort of a nasty agorophiid-like dolphin.

A partial odontocete skeleton.

A beautiful xenorophid skull on display. Look at those teeth!

Some kind of a sea turtle - identified as Procolpochelys.

A skull of the sea turtle Carolinachelys.

Coming up next - I found some more photos from Charleston, so there will be STILL more from the US trip (I was gone for a whole month, I might as well talk about it). Also: reviews of some recent research by M. Churchill, R. Racicot, G. Aguirre, and N. A. Smith, and more on Osedax and taphonomy.

2012 in Review: Advances in Marine Mammal Paleontology

2012-12-31T18:32:00.001-07:00

Even though it's already twelve or so hours into 2013 here, since most of my readers are still in 2012 at the moment I thought I'd take some time to do a brief review of new research on fossil marine mammals published during the last year. It's been a good year for the pygmy right whale, and sirenians. Not much has been done with fossil pinnipeds, unfortunately (but stay tuned... especially around mid-January...).

I'm doing this in alphabetical order of the author's last name - so I promise that a taphonomic article coming first does not reflect my own bias. Early in the year Zain Belaústegui and colleagues published on a Miocene mysticete skeleton in PPP which was not only articulated, but also had a number of flask-shaped Gastrochoenolites borings in it. Such borings are common in marine mammal bones, particularly those from lag deposits like the Red Crag in eastern England, as well as the Santa Margarita Sandstone in California. But bored remains from those units are all allochthonous, and the fact that the skeleton was still articulated meant that it was autochthonous, which is a pretty surprising find in my opinion. They also did a great job at summarizing previously published biogenic bone modifications (admittedly a better job than I did in my bite marks paper).

I've already covered Michelangelo Bisconti's publication in Zoological Journal of the Linnean Society on the new neobalaenid (or neobalaenine...?) genus Miocaperea from Peru, which you can check out here. Miocaperea is not the first pygmy right whale to be reported from the fossil record (see below), but it is the first non-fragmentary specimen - and at 7-8 million years old, it indicates that the modern Caperea morphology has been around for a long time.

Although technically not published yet, a recent paper in PPP (online early) by Mark Clementz, my adviser Ewan Fordyce, UW student Stephanie Peek, and UM professor David Fox (who during the 2009 MSU geology field camp final mapping project, I ran into out at Frying Pan Gulch - the U. Minnesota field camp was out there at the same time; Dave is a co-supervisor for my good friend and taphonomy cohort Laura Vietti's Ph.D.) focuses on oxygen and carbon isotopes of Oligocene cetaceans from New Zealand and South Carolina. They studied odontocetes, toothed mysticetes, toothless mysticetes, and the enigmatic kekenodontids (the surprisingly dorudontine-like Kekenodon sp. in above photo). Among their findings - kekenodontid isotopes changed from anterior teeth to posterior, probably reflecting ontogenetic changes from nursing to adult feeding. Low O and C isotope levels for toothless mysticetes were similar to modern mysticetes, suggesting that they already were migrating along a latitudinal gradient, and that toothed mysticetes and odontocetes were "resident" rather than transient populations.

Another paper that just recently came out by my colleague Julia Fahlke in Palaeo-Electronica uses 3D digital models to reconstruct feeding by Basilosaurus on Dorudon, based on several skulls of juvenile Dorudon with large bite marks. The mouth of Basilosaurus was opened and the skulls of poor baby Dorudon rotated until possible fits were found. A pretty neat paper with some great graphics.

Another paper on fossil neobalaenids - which I've also already talked about. This is the first reported find of a neobalaenid (pygmy right whale) in the fossil record, published by Erich Fitzgerald in JVP.

Yet another paper about Caperea... which I just posted about last week, and you can check it out here. This paper came out last week in Proceedings of the Royal Society B, published by R.E. Fordyce and Felix Marx, and includes a new phylogenetic analysis and presents the hypothesis that the modern pygmy right whale is the sole surviving member of the (formerly extinct) family Cetotheriidae.

Jonathan Geisler and colleagues published in JVP over the summer a new genus of iniid river dolphin, Meherrinia, from the Meherrin River, North Carolina, represented by numerous (about a dozen) partial skulls. At SVP in Raleigh this year, Jonathan, Brian Beatty, and Carl Mehling visited a local collector who had several more specimens he donated - in addition to some other great stuff. Meherrinia is the first diagnostic iniid fossil reported from marine rocks.

Ukrainian colleague Pavel Gol'Din and coauthor K.A. Vishnyakova published an article in APP (still in the forthcoming articles section) on a high latitude record of the southern hemisphere beaked whale Africanacetus, previously reported by Bianucci et al. (2007) from the South African continental shelf. The fossil is the highest-latitude record of a beaked whale in the fossil record, and is 6000 km from the type locality, suggesting it had a circum-antarctic distribution. Unfortunately, the age of these specimens - like the South African material - is totally unknown, but assumed to be Neogene in age.

A Pleistocene record of a bottlenose dolphin (Tursiops sp.) was reported on by Toshiyuki Kimura and colleages in the Bulletin of the Gunma Museum. Pleistocene records of marine mammals are fairly rare, and such as in this case, are mostly composed of extant genera and species.

The only paper this year (to my knowledge) on fossil pinnipeds was published by Irina Koretsky and colleagues in the journal Deinsea. In it they describe a new species of the early phocid Leptophoca from both sides of the atlantic - Leptophoca amphiatlantica, based on isolated femora. The new species is found in the Calvert Formation and Saint Mary's Formation of Maryland and Virginia, and the Miocene Upper North Sea Group in the Netherlands (from the "Hoojdonk sandpit", a whimsical name to non-dutch speakers like myself). However, it's unclear exactly how much taxonomic utility is preserved in isolated postcrania.

Korean paleontologists Y.M. Lee, D.K. Choi, and former Otago student Hiroto Ichishima published on a middle Miocene platanistid from south Korea in JVP. This new specimen is just a fragmentary (but well preserved) rostrum - at first glance, some folks would be hard pressed to tell whether this was a dolphin or an ichthyosaur. They identified this specimen as a pomatodelphine (including the Floridan fossil dolphin Pomatodelphis) rather than an allodelphinid dolphin based on tooth morphology. This is interesting, as allodelphinids are already known from the early and middle Miocene of California - but pomatodelphines are not yet known from the Pacific, giving this interesting biogeographic implications.

Japanese colleague Mizuki Murakami recently published parts of his dissertation undertaken at Waseda University regarding fossil porpoises (Phocoenidae) from Japan. He described three new genera between two articles published in the same issue of JVP: Archaeophocoena, Miophocoena, and Pterophocoena. In one of these articles, he reconstructs the facial evolution of phocoenids and other delphinoids in painstaking detail, and in the other, conducts a detailed phylogenetic analysis of delphinoids, with interesting phylogenetic results. It's also the first analysis to include fossil monodontids Denebola and Bohaskaia, as well as the bizarre creature Odobenocetops (which plots out as sister to the monodontids).

A paper in the works for a long time came to fruition this year: Yoshihiko Okazaki (Kitakyushu Museum) described a new eomysticetid from Japan which he named Yamatocetus canaliculatus. It is similar in many regards to Eomysticetus - and is more complete, and has a partial postcranial skeleton. I really ought to talk about this one in more detail later. Aside from all the usual weirdness of an eomysticetid, this taxon also appears to retain individual alveoli, which Okazaki interpreted as housing reduced teeth during life.

Silvia Sorbi and colleagues published on new remains of Metaxytherium subapennum, the geochronologically youngest sirenian in the Mediterranean and youngest species of Metaxytherium. Metaxytherium is principally a middle-late Miocene dugongid - but one relict species persisted in the Mediterranean, even after dwarfism triggered by the Messinian Salinity Crisis (for the uninitiated, the Mediterranean nearly dried up at the Mio-Pliocene boundary), and reflooding of the Mediterranean. Responding to reestablishment of the Mediterranean Sea, Metaxytherium subapennum increased in body size from its ancestors. Unlike hydrodamaline dugongids in the North Pacific, Metaxytherium subapennum was unable to adapt to colder climates and went extinct during the middle Pliocene.

Two recent papers by Tarasenko and Lopatin published in the Palaeontological Journal focus on new records of cetotheriid baleen whales from the Northern Caucasus. Two new genera were reported: Kurdalogonus from Adygea, and Vampalus from Chechnya. For the lazy, these regions of the Russian Federation lie between eastern Ukraine/Black Sea and western Kazakhstan/Caspian Sea. Kurdalogonus in some ways is very similar to Cetotherium rathkei, another cetotheriid from the former Paratethys (Ukraine to be exact). Vampalus, on the other hand, is a bit more of a freak, and was identified as a herpetocetine - although no phylogenetic analysis was conducted (although the earbones, I think, are a bit of a selling point for me). It definitely has some weird stuff going on with the braincase, and in some ways looks like a cross between a herpetocetine and an aetiocetid.

Still with me? Almost done. Early on this year, my good friend Jorge Velez-Juarbe and Nick Pyenson published in JVP a new genus of fossil monodontid, which they named after USNM collections manager Dave Bohaska. I had the pleasure of meeting Dave in October - he's very entertaining and quite a character, and goes above and beyond the call of duty to make sure you have a productive/successful USNM visit, tracking down all sorts of obscure fossils, opening storage jackets, etc. The fossil was collected in the 1960's from the Yorktown Formation at Rice's Pit in Virginia, where the type specimen of Balaena ricei was also collected. Since it was not from the Yorktown at Lee Creek, this specimen was not described by Whitmore and Kaltenbach (2008) in the Lee Creek IV volume, where they described all sorts of monodontid earbones and partial skulls/mandibles as Delphinapterus (modern beluga). Now it appears that two monodontids were present (or, alternatively, everything may be referable to Bohaskaia).

Another paper by Jorge and colleagues early in the year, published in PLOS One. This paper discusses feeding ecology in three sympatric sirenian assemblages from the late Oligocene of Florida, early Miocene of India, and early Pliocene of Mexico. Each of these assemblages included three dugongid sea cows, and although body size and certain feeding adaptations did overlap in each assemblage, at least one consistent difference was present in each. Modern sirenians do not geographically overlap, and these assemblages appear to have evolved iteratively during the Cenozoic - in other words, different niches were haphazardly 'filled' by different species of dugongids through time (rather than the small bodied taxa being closely related and vice versa).

And another sirenian study to finish off 2012. German researcher Manja Voss recently published in Palaeontologische Zeitschrift on a new skeleton of Halitherium schinzii from the early Oligocene of western Germany. This specimen suggests that some taxonomic revision for the species is required. Interestingly, some figures in this paper look like there are Osedax pockmarks on the bones of this animal.

Have a productive 2013 - I didn't get anything published in 2012, although as alluded to above, keep your eyes peeled mid-January; I've got three other papers in review at the moment, and a couple more nearing submission, so 2013 is going to be a good year for me, I can tell already.

Some of these studies I really ought to talk about in further detail, but I'm sick of typing (and if you're a healthy human being, you're probably sick of reading this). In any event, it's New Year's Eve, stop reading the internet and go to a party already!

US research trip part 9: Charleston, South Carolina, and the Charleston Museum

2012-12-28T16:41:00.001-07:00

Given my research focus on eomysticetid baleen whales, it was necessary for me at some point during my Ph.D. to travel to Charleston, South Carolina, to visit Al Sanders and photograph the holotype of Eomysticetus whitmorei. This was the number one objective for my entire month-long excursion. I absolutely loved Charleston, and would love to have an excuse to return.

We moved to New Zealand in March, after a short California winter and after about a month of "nice" weather in Dunedin, were plunged back into four months of winter - we basically had an entire year of winter. Oddly enough, even though it was late October, my visit to Charleston was the first time I felt warm outside since my move to New Zealand. It was also the first time in a long while I could comfortably wear a T-shirt at night in a long while. I really enjoyed Charleston - it's a beautiful city, with so many historical buildings you nearly trip over them.

St. Michael's Episcopal Church, the oldest church in Charleston, built in the 1750's. The plaque on the side of the church claimed several signers of the Declaration of Independence as members (several of whom were interred in the adjoining cemetery).

Fort Sumter, as viewed from waterfront park on the east side of Charleston. It's the tiny one on the right, next to the radio antenna. For the uninitiated, the American Civil War began right here in Charleston with the bombardment of the Union-held Fort Sumter (technically, the civil war opened with Citadel cadets firing upon the Union ship Star of the West). It was pretty neat seeing current students jogging around town in "Citadel" sweats (Citadel is a military academy). Just north of St. Michael's church in Charleston, you can find a plaque indicating that the previous building on the site was used for the South Carolina Assembly, where the political leaders of the state voted to become the first state to secede from the Union, shortly following the election of Lincoln.

Speaking of the civil war and all things aquatic, here's the world's first submarine to successfully sink an enemy ship, the H.L. Hunley - it's about 2 meters in diameter and about 5 meters long or so... I would not have wanted to be a crewmember (least of which because the Hunley sank several times, including after it sank the Housatonic). The first operational submarine - the Turtle - was also an American vessel, dating from the American Revolution, where it unsuccessfully attempted to sink a British ship in Boston Harbor. The Charleston Museum is the oldest museum in the United States, and was established in 1773 - to put it another way, it's doors had nearly been open for an entire century before the Civil War began.

Ah, finally onto fossils and "older" endeavors. Although the Charleston Museum primarily bills itself as a history museum, with a focus on Civil War history - it has extensive collections of Oligocene and Pleistocene mammals and marine vertebrates, mostly due to the efforts of recently retired natural history curator Al Sanders, who I had the pleasure of meeting during this trip (Al had also attended the 2006 SVP meeting, but as a shy undergrad I didn't introduce myself). Here, Ewan Fordyce is photographing parts of the holotype skull of Eomysticetus.

Because the SVP meeting was held in Raleigh, North Carolina, two other paleocetologists decided it would be an opportune time to make the trip south to Charleston. My friend Eric Ekdale (postdoc at San Diego State/San Diego NHM; with camera) flew down, and I had the privilege of driving down Ewan and former Otago Ph.D. student Tatsuro Ando, now at the Ashoro Museum of Paleontology (in background). A week earlier I politely asked Ewan if he knew how to drive on the right hand side of the road; when he explained that he learned to do so during his postdoc in Washington D.C. (before I was born), I made a mental note that I'd be the one driving from Raleigh to Charleston.

Ewan and Eric maneuver the skull parts of Eomysticetus.

Retired curator Al Sanders and current collections manager Jennifer chat in collections

during our visit.

Eric examining the holotype petrosal of Eomysticetus; other earbones including the Micromysticetus type petrosal sit on the table.

A quick pause during furious note taking at the Charleston Museum; the holotype of Micromysticetus rothauseni sits next to my notebook.

The holotype of the diminutive mysticete Micromysticetus rothauseni, with both petrosals in articulation. It's a beautiful, if incomplete skull.

One of the infamous Oligocene seal femora from the Chandler Bridge/Ashley Formations, which I've discussed previously. It was nice to see the actual specimen.

The Charleston Museum does have a handful of paleontology related exhibits, although you still wouldn't have any idea from the exhibits that there were any fossils in collections. Here's a spectacular squalodontid, similar in size to our NZ squalodontid. This is a pretty scary looking beast.

A mount of an undescribed pelagornithid from the Chandler Bridge Formation; this one is also on display at the USNM. If I'd had time, I would have loved to have photographed the original specimen.

A mounted cast of the skeleton of Gavialosuchus, also a pretty fearsome looking creature. I think eomysticetids were the only things preserved in the Chandler Bridge that didn't have big sharp point teeth (or pseudo teeth for that matter). Actually, that may not be entirely true (stay tuned for a future post on the eomysticetid Yamatocetus canaliculatus for more on that...).

Evolution of the pygmy right whale Caperea and the resurrection of the Cetotheriidae from extinction

2012-12-22T06:20:00.005-07:00

I have a special place in my heart for small baleen whales. Large baleen whales have skulls (modern and fossil) that are just a pain in the ass to examine, move, photograph, measure, or excavate. When I first got started with marine mammal paleontology as an undergraduate, baleen whale earbones were great to work with as they still provide reasonable phylogenetic information, but are easy to identify in the field, easier to collect than complete skulls, and when a significant collection of them is established, inferring the diversity of a baleen whale assemblage is elementary. The discovery of a well preserved skull of Herpetocetus bramblei in the Purisima Formation in June 2007 (and to a lesser extent, a mandible of the same species from the preceding summer) catapulted me into the study of fossil cetotheriid mysticetes. Cetotheres were formerly considered a wastebasket group, a neglected heap of misfit toothless mysticetes that didn’t belong in modern families. These were found to belong to two phylogenetic groups: one monophyletic clade termed the Cetotheriidae sensu stricto (Cetotherium, Piscobalaena, Herpetocetus), and another group forming a paraphyletic group of early balaenopteroids, sometimes jokingly referred to as “Kelloggitheres” (Parietobalaena, Diorocetus, Pelocetus). Given my interest in true cetotheres, I was pleased to see the publication of a new article in Proceedings of the Royal Society by my adviser Ewan Fordyce and fellow labmate Felix Marx on a phylogenetic reinterpretation of the modern pygmy right whale, Caperea marginata, as an extant cetothere.

The skeleton of the pygmy right whale, Caperea marginata. From Bisconti (2012).

The modern pygmy right whale inhabits the southern ocean, and is rarely observed alive; as of 2008, only 25 sightings of Caperea have been made at sea. We know more about Caperea from dead individuals than live ones – much like working with fossils. Caperea is approximately 5-6 meters in length as an adult, dark gray, and bears a bowed rostrum with long baleen, like balaenid right whales (true right whales). Caperea feeds on copepods and euphausiids, probably employing a similar skim feeding behavior as in right whales. Unlike balaenids, the pygmy right has a falcate dorsal fin. Caperea has on rare occasions been observed in massive gregarious accumulations. The skeleton of Caperea is one of the most distinct among baleen whales: an extreme degree of cranial telescoping, a relatively short rostrum, nearly absent zygomatic processes of the squamosal, mandibles that are transversely flattened with a sinusoidal outline, bizarre earbones, posterior ribs that are expanded and flattened, and transverse processes of the lumbar vertebrae that are expanded into canoe-paddle shapes and overlap one another.

Phylogenetic results from Fordyce and Marx (2012), showing the revised phylogenetic position of Caperea marginata as a cetotheriid.

Comparison of the skulls of Caperea marginata (above) and Herpetocetus transatlanticus (below) in dorsal (left) and ventral (right) views. From Fordyce and Marx (2012).

Two previous phylogenetic hypotheses for the pygmy right whale exist. As the common name implies, morphologists have historically considered it to be related to the Balaenidae – forming a clade called the Balaenoidea. Most previous phylogenetic analyses have supported a monophyletic Balaenoidea (see summary in Churchill et al., 2012). However, molecular analyses have generally failed to yield such a relationship, and instead have found Caperea to be slightly more closely related to balaenopteroid mysticetes rather than balaenids. A recent morphological analysis by Felix Marx (2011) resulted in this intermediate position, unique among morphological analyses. In his phylogeny, Caperea showed up as a sister to the balaenopteroids, with cetotheriids, “kelloggitheres”, and balaenids further down the tree. In the new phylogeny by Fordyce and Marx (2012), Caperea was bumped down one node on the tree into the Cetotheriidae – and as a sister taxon to the Herpetocetinae in particular (Nannocetus + Herpetocetus). This resulted from the reinterpretation of several anatomical features, based on new observations of the skull morphology of Caperea. For example, cetotheriids and Caperea share a plug-like extension of the petrosal (earbone) that is exposed on the lateral surface of the skull. Like Herpetocetus, a large flange of the petrosal sticks out laterally and articulates with the squamosal bone. Certain features are obvious only in juveniles, and are obliterated during ontogeny by changes in skull shape. For example, juvenile Caperea show a rectangular extension of the maxilla that extends toward the top of the skull; this is a feature that is absent in all modern and fossil balaenids, but present in cetotheriids and balaenopteroids. Many other characters relating to the basicranium were interpreted as similar in cetotheriids, which in the analysis pulled Caperea into the Cetotheriidae.

Comparison of the earbones of Caperea marginata (left) and Herpetocetus transatlanticus (right); petrosal in articulation with squamosal above, and tympanic below. From Fordyce and Marx (2012).

So what’s so important about the reclassification of Caperea as a cetotheriid? For one, it allies a modern baleen whale with a group formerly considered to be totally extinct. The last member of the family – Herpetocetus – lasted until about 2 million years ago in the eastern North Pacific. I’m not so certain that Caperea is necessarily so closely related to the herpetocetines in particular – the fossil neobalaenid Miocaperea is contemporaneous with the oldest herpetocetine, Nannocetus eremus, and is already extremely derived; indeed, the case for it requiring a genus separate from Caperea is thin. This indicates that the hallmark pygmy right whale morphology had already evolved by the time derived herpetocetines evolved – suggesting if anything that these two groups (pygmy right whales, and herpetocetines) evolved in parallel. Neobalaenines paralleled the morphology of herpetocetines, separated from the herpetocetines in the southern hemisphere. It is unclear whether or not herpetocetines utilized a similar feeding ecology – but it is fascinating to imagine the northern hemisphere analog of Caperea going extinct at the end of the Pliocene, and the only straggler of a formerly more diverse group of dwarf baleen whales surviving in the southern ocean.

US Research trip part 8: USNM osteology and mammal halls

2012-12-19T16:48:00.002-07:00

Although a marine vertebrate specialist like myself can and will stare and drool at the mounts of fossil marine birds, reptiles, and mammals in some of the Smithsonian's halls, it is healthy to occasionally venture out and look at terrestrial mammals, other birds, and even modern fish. Well, as you'll see from the following photos, I spent most of my time taking pictures of modern marine bird and mammal skeletons anyway (oops), although I promise to my former MSU cohorts that I did spend some time looking at dinosaur skeletons (gasp!) but didn't waste any memory card space on them.

The king of the jungle, er, savannah. Beautiful mount of Panthera leo, USNM mammals hall.

The real king of the savannah, Loxodonta. It's only fair that this is the centerpiece

of the USNM rotunda.

Back to marine mammals. Skeleton of the Fransiscana/La Plata River Dolphin, Pontoporia blainvillei. My wife just calls it (and the Californian fossil Parapontoporia) "Francis". Smithsonian Osteology hall.

A menagerie of pinnipeds: a walrus skull, a Steller's sea lion skull (Eumetopias jubatus), and my favorite pinniped, the northern fur seal, Callorhinus ursinus. I love this mounted skeleton. Smithsonian Osteology hall.

Side-by-side comparison of a sea otter (Enhydra lutra) and a river otter (Lontra canadensis). I really ought to get some work done on my Pleistocene sea otter project... Smithsonian Osteology hall.

A fantastic display showing the homology of different skull bones, showing a fish, giant salamander (or is it a goliath frog?), an alligator, a bobcat, and some kind of bird. Smithsonian Osteology hall.

A member of one of my favorite groups: an alcid, the razorbill Alca torda. The closest modern relative of the extinct Great Auk, Pinguinus impennis. Smithsonian Osteology hall.

A big beautiful swordfish, Xiphias gladius. Billfish (swordfish, marlins, and sailfish) are common fossils in some sediments.

One of the most spectacular modern mammals on display at the USNM: one of the few known skeletons of the extinct Steller's sea cow, Hydrodamalis gigas. A modern Dugong dugon on the lower right for scale.

As a surrogate New Zealander, I feel obligated to include this picture of an Apteryx skeleton.

Lastly, a barndoor skate, Raja - I love mounted chondrichthyan skeletons. I like seeing mounted or preserved specimens of Raja, because I've collected numerous calcified mandibular cartilages of a Pliocene Raja from the Purisima Formation in California (see Boessenecker, 2011).

What's up next? A summary of Ewan Fordyce and Felix Marx's new paper in Proceedings B regarding the phylogenetic placement of Caperea, the Pygmy Right Whale. After, two more posts of photos from research in Charleston, South Carolina, and then we'll be back to "normal programming".

US Research trip part 7: USNM ocean hall and hall of marine life exhibits

2012-12-17T01:36:00.002-07:00

I first visited the Smithsonian Natural History Museum in 2005 when I was an undergraduate, and didn't exactly have a great camera at the time. In the time being, the new Sant Ocean Hall has been installed, which includes a number of great exhibits on modern and fossil marine organisms. Here are a collection of photos I took in the Hall of Marine Life and the Sant Ocean Hall at the Smithsonian during my trip.

A beautiful mount of a sailfish (Istiophorus) in the new Sant Ocean Hall.

A sculpture of a northern right whale (Eubalaena japonica) in the Sant Ocean Hall.

A familiar face! This is a cast of the skull of the early toothed mysticete Llanocetus denticrenatus from the latest Eocene of Seymour Island, Antarctica. The skull was collected by Ewan Fordyce in Summer 1986 on an antarctic expedition. We have the original (and a cast) here in our department, currently under study by Ewan.

The holotype mandibular fragment of Llanocetus denticrenatus, collected on an earlier expedition and named by Ed Mitchell in 1989.

A mounted cast of the skeleton of the Egyptian basilosaurid archaeocete Dorudon atrox.

A mounted skeleton of the Eocene protocetid archaeocete Maiacetus inuus from Pakistan. This is a cast of the male individual; the female - the "Good Mother Whale" - was found with the skeleton of a near term fetus inside.

A giant or Japanese spider crab, Macrocheira kaempferi, in the Sant Ocean Hall - nightmare fuel for my wife.

Dolly! Or, Dolichorhynchops as she's known to the marine reptile community. A 3-4 meter long short necked pliosaur.

Skeleton of the basilosaurid Zygorhiza from the Eocene of the southeastern US. It's about a 5 meter long animal with pretty gnarly teeth (as with all basilosaurids).

And here's the skull of Zygorhiza. It retains some primitive features, such as teeth below the orbit and heterodonty (teeth of different morphologies such as incisors, molars, etc), and several adcanced features like a posteriorly shifted bony naris and reduced hindlimbs.

The paratype skull of Diorocetus hiatus, described by Remington Kellogg in the 1960's, from the Calvert Formation of Maryland. I saw the holotype, and as mentioned in a previous post, parts of it are mostly sculpted.

Mounted skeleton of the strange Miocene pinniped Acrophoca longirostris from Peru. This long-snouted seal is well known from the Pisco Formation, and has something to do with the evolution of modern antarctic lobodontine seals.

An undescribed species of Spheniscus penguin, also from the Pisco Formation of Peru.

An early type of different flightless bird - a cast of Hesperornis, a very well known toothed swimming bird from the "middle" Cretaceous of North America, first described by O.C. Marsh from the Niobrara Formation.

Some pretty pencil urchin.

A preserved adult and juvenile coelacanth (Latimeria), a living fossil. For the uninitiated - coelacanths were known from the fossil record (Triassic, Jurassic, and Cretaceous), but thought to have gone extinct at the K/Pg boundary along with nonavian dinosaurs and other groups (e.g. ammonites, mosasaurs); a live specimen was caught off South Africa in the 1930's.

US Research trip part 6: out and about in DC

2012-12-10T17:21:00.001-07:00

As a US citizen it's pretty inspiring to walk around Washington DC and see all of these famous buildings and monuments in our nation's capitol. Unfortunately, while I did eat at this great diner across the street from Ford's Theater (where Lincoln was assassinated) I forgot to take some pictures. I also didn't get a chance to visit the house where The Exorcist was filmed, right in Georgetown. Either way, I saw plenty of other great stuff.

The white house! Being two weeks before the election, I was sincerely hoping that Obama would not have to move out soon.

Outside the White House. Maybe he was a Romney voter?

Looking down Pennsylvania Ave. towards the U.S. Capitol building.

The south lawn of the White House. Just to the left of this photo is Michelle's vegetable garden.

A look down Constitution Avenue from near the Washington Monument; the Department of Justice and IRS are based in these red-roofed buildings.

America! Flags next to the Washington Monument.

View west from the Washington Monument past the World War II monument and reflecting pool to the Lincoln Memorial.

Monument to Ulysses S. Grant, just west of the capitol building.

East side of the U.S. capitol building.

The national archives - they had an exhibit on the cuban missile crisis which I did not have time to visit. This is pretty close to the USNM, and I walked past this neat building every day to the metro station.

There was only one example of graffiti on the World War II memorial. This was a common graffiti cartoon that was done in Europe by GI's in random places. This example was intentionally engraved onto the WWII memorial.

The Lincoln Memorial - 8 hours before Hurricane Sandy made landfall.

The statue of Lincoln in the memorial.

The elegantly simple Vietnam memorial wall.