The Coastal Paleontologist returns

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

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

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

Watch the entire talk here on youtube here:

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

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

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

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

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

2025 in review: advances in marine mammal paleontology

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Viglino andPark – River dolphin cochlea has not evolved convergently.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

In 1937, Professor William B. Benham of the Department of Zoology at the University of Otago published a short paper naming the new cetacean Lophocephalus parki, based on a broken braincase from an unknown locality, but most likely the Milburn Limestone at the Milburn Lime Quarry just about 40 km southwest of Dunedin (and, for anyone flying in to the country, quite close to the airport). Professor Benham noted that the skull was clearly not from a "squalodont" - which, as you may have guessed from part 1, and will be expanded upon in part 2, most heterodont cetaceans from the Oligocene and early Miocene were identified as "squalodonts" - but did not initially consider it to be a baleen whale. Based on the sagittal crest and narrow occipital shield, he considered Lophocephalus (ridged head, after the tall muscle attachment crests) to be an archaeocete whale. Another specimen, which he thought was from Lophocephalus, included a partial mandible and some blocks of limestone with associated teeth - Benham assumed these were from the same species, writing "I think I am justified in associating these teeth with those from Waimate, and attributing them to Lophocephalus parki."

The unassuming fragmentary braincase of Lophocephalus parki, from Benham (1937).

Benham's (1937) initial interpretation of Lophocephalus parki as an enormous archaeocete. Correspondence with Remington Kellogg would pointed out that the frontoparietal suture is present in the fragment, meaning that the skull is considerably more telescoped than Benham thought, and that it represented a mysticete.

Some of the specimens that Benham (1937) initially referred to Lophocephalus parki - a completely reasonable action given that he thought it was an archaeocete. Later it would become obvious that these were in fact odontocete specimens, now considered Squalodon or something similar.

This conclusion, however, was fleeting. Benham wrote a followup paper five years later in 1942 that precipitated from letters he had received from Remington Kellogg of the Smithsonian Institution in 1940. Kellogg pointed out that the braincase was much more complete than had been assumed by Benham, who had missed the frontal-parietal suture, though clearly present in his published photographs. Kellogg wrote that the skull was rather similar to Aglaocetus moreni, redescribed and illustrated by Kellogg in 1934. Further, Benham (1942) wrote that "after distribution of reprints of that article, my attention was drawn by a zoologist in America to the devastating fact - which I confess I had overlooked - that this generic name [meaning the genus name Lophocephalus] had been bestowed already on three animals of widely different groups, viz., on a Gregnarine, on a beetle, and on a fish! Hence, it is necessary to substitute another name for this extinct whale." Benham recognized that the specimen was in fact a baleen whale, and named it Mauicetus parki. Benham (1942) was forced to essentially re-publish a basic description of the fossil owing to the fact that, at the time, it was typical for descriptions to essentially consist of a long list of comparisons, his mistaken identity in 1937 sadly resulting in some anatomical misinterpretations that made the original study practically useless in most regards. In the 1942 redescription, Benham makes extensive comparisons with Aglaocetus moreni, and concludes that, thanks to Kellogg's correspondence, Mauicetus parki is indeed a "cetothere".

Cheng-Hsiu Tsai examining the postcranial bones of ZMT 67, a very large Mauicetus-like mysticete from the very top of the Otekaike Limestone, dating to the lowermost Miocene (Aquitanian). The specimen is still undescribed and was the focus of Hiroto Ichishima's doctoral thesis at Otago.

How do you photograph a whale skull? Lots of lighting, and by using the stairwell outside Ewan's office! Ewan had a homemade wooden clamp to clamp is camera onto the wooden railing, and depending upon the size of the whale, we would use either the lower or the upper railing nearer the first floor (=second floor in America). Here Felix and Ewan have an elaborate lighting setup, including the use of foam to bounce light to maintain correct lighting from the upper left (I presume the skull was intended to be oriented with its nose pointing to the left side of the figure). This is the referred juvenile skull of Mauicetus parki.

Ewan Fordyce and colleagues would go on to find many more Mauicetus-like fossils, including some fragmentary specimens reported by Hiroto Ichishima in his (unpublished) doctoral thesis. One specimen, collected not by Ewan but by F.M. Climo and colleagues in 1971, ZMT 67, is a large, 2.5 meter long partial skull with some postcrania that represents either a species of Mauicetus or a closely related genus. This specimen is earliest Miocene in age and from the very top of the Otekaike Limestone. In 2004 or so, Ewan and field assistants excavated a partial skull of a juvenile Mauicetus parki from Haugh's Quarry in the Hakataramea Valley of South Canterbury. He presented this in his 2005 presentation at the Society of Vertebrate Paleontology meeting in Mesa (Phoenix) Arizona, my first SVP - ten of us undergraduate students from Montana State University had carpooled down from Bozeman on a group road trip, taking turns napping and driving, in a 14 hour trek. I had been interested in fossil marine mammals, and just finished my first field season of permitted field work - and eagerly attended the marine mammal session on the morning of the second day. I saw a talk by Phil Gingerich on the giant archaeocete Basilosaurus isis from Egypt, a talk by Larry Barnes on kentriodontid dolphins from Calvert Cliffs, a talk from Mark Uhen on xenorophid dolphins from Onslow Beach, North Carolina (published three years later as Albertocetus), and a talk by Ewan Fordyce on a mysticete skull from New Zealand. I was shocked as Ewan described how he would excavate these specimens from the soft, sandy limestone with a chain saw. The entire excavation - which would have taken a crew of 3-4 pick/chisel-armed graduate students 3-4 days to excavate - took Ewan only about 2-3 hours! This material is still not yet published, unfortunately, but my doctoral labmate Felix Marx is continuing Ewan's research on Mauicetus. All I can say about Mauicetus parki is that it has an acutely triangular occipital shield, and earbones and mandibles that are similar to but slightly more primitive-looking than those in American "cetotheres" like Diorocetus and Parietobalaena. One of the key features I can mention is that Mauicetus has one critical earbone feature that is shared with modern baleen whales, to the exclusion of toothed mysticetes and eomysticetids: the posterior process of the two earbones (periotic and bulla) are fused into a long, cylindrical process. Near the base of this structure, the elliptical foramen in the bulla is also closed up. Mauicetus is the oldest known mysticete with these features.

The holotype skull of "Mauicetus" lophocephalus, from Marples (1956): on the right, the skull is shown as it was discovered and excavated in the Kokoamu Greensand. On the left is the skull as it was prepared, prior to being lost sometime in the 1960s or 1970s. At first glance, the skull of Mauicetus parki looks rather similar...

The holotype tympanic bulla of "Mauicetus" lophocephalus, from Marples (1956). Very obviously an archaic mysticete given how similar it is to basilosaurid whales.

The holotype atlas and axis vertebrae of "Mauicetus" lophocephalus (left) and "Mauicetus" waitakiensis (right), from Marples (1956).

More Mauicetus, of Marples: Mauicetus lophocephalus, Mauicetus waitakiensis, and Mauicetus brevicollis

Professor Brian J. Marples of the University of Otago Zoology Department was an accidental paleontologist. He was actually an arachnologist - specializing in the zoology of trap-door spiders in New Zealand. In the 1940s, his work on these spiders brought his nose to the ground in the vicinity of the Waitaki River - and Oligocene rock layers. As a result, he and his students discovered some interesting cetacean and penguin fossils. He published on some of the fossil penguins in 1952, identifying them as Palaeeudyptes antarcticus. These identifications were determined later to be too conservative, and several were named as new species after Marples (by none other than G.G. Simposon) along with the new genus Marplesornis. Marples also found several baleen whale specimens consisting of partial skeletons, which he named in a 1956 paper, all from the Kokoamu Greensand (Duntroonian stage, 27-25 Ma). The most spectacular of these was named Mauicetus lophocephalus - amusingly re-using Benham's original genus name for Mauicetus - based on a partial skull with mandibles, periotic fragment, tympanic bullae, and some neck vertebra. A somewhat more fragmentary specimen consisting of the occipital bone, tympanic bullae, and neck vertebrae was named Mauicetus waitakiensis, and a third specimen consisting of a string of vertebrae was named Mauicetus brevicollis. Mauicetus lophocephalus was unusual in having a relatively primitive looking skull, and three images were produced: a photograph of the specimen in situ as it was discovered, a photograph of the braincase, unfortunately missing most of the rostrum which was apparently destroyed during excavation. The third image is a line drawing, which Fordyce suspected Marples drew while in the field - giving us a near-accurate view of the outline of the complete skull. The skull has a triangular rostrum, very long nasals and a bony naris (blowhole) set far out on the rostrum, large temporal fossae with medially bowed zygomatic arches, and a narrow intertemporal region of the skull with a small, narrow, posteriorly positioned occipital shield and vertex. Another skull resembling this would not be discovered again in New Zealand - or elsewhere on earth - until the 1980s.

The holotype skeleton of Horopeta umarere, from Tsai and Fordyce (2015): fossil locality, the excavation of it and a manmade cave in the Otekaike Limestone, and the specimen before and after final preparation by Tsai. I believe Craig Jones is the man in the hole.

The unusually robust sternum of Horopeta umarere. It retains an archaic rod-like structure with expansions at either end, and articular facets for multiple pairs of ribs; eomysticetids, on the other hand, had plate-like, triangular sterna with no obvious deep facets like this, implying only a single lightly attached pair of ribs as seen in the rest of Crown Mysticeti. From Tsai and Fordyce (2015).

Horopeta umarere - the oldest known gulp-feeding mysticete

A large mysticete was excavated from a cliff on the southeast side of Haugh's Quarry in 1988 by Ewan and his preparators Andrew Grebneff and Craig Jones. This specimen has a partial braincase, very well-preserved earbones, partially preserved mandibles, a sternum, and an articulated vertebral column with some ribs. This specimen served as the core specimen in my labmate Cheng-Hsiu Tsai's doctoral thesis, sort of a 'sequel' to Ichishima's 1997 thesis, and was published by Tsai and Fordyce in 2015. They named it Horopeta umarere roughly - translating from Maori to gulper with an unusual sternum . The specimen is from the base of the Duntroonian in the Kokoamu Greensand, dating to around 27-26 Ma. The skull is similar to Mauicetus, as are the earbones - yet they exhibit some features more reminiscent of eomysticetids: there is an open elliptical foramen in the bulla, and the posterior processes are not yet fused. However, the real revelation comes from the mandibles - they are robust, with a D-shaped cross-section, have a large and laterally curving coronoid process and are laterally very strongly bowed - much more strongly bowed than in eomysticetids, and resembling some Miocene "cetotheres" sensu lato ("kelloggitheres") as well as modern balaenopterid whales. This enormous mouth indicates that Horopeta was strongly adapted towards 'gulp feeding' - a more descriptively neutral term for a whale that takes in great mouthfuls of water to filter feed, like the lunge feeding behavior of modern balaenopterids. The sternum is quite robust and rod-like, with attachment points for three ribs - quite different from the plate-like sternum with an attachment for a single pair of ribs in modern mysticetes. Mysticetes tend to only have a single sternal bone - the manubrium, the anteriormost sternal bone, and all of the others, including the posteriormost one, the xiphisternum, are lost. Like other early mysticetes, there doesn't appear to ben articulation for a second sternal body. The robustness of the sternum in Horopeta is quite similar to toothed mysticetes like Llanocetus, Aetiocetus, and Mammalodon, and generally quite different from eomysticetids and modern mysticetes, suggesting a reversal or parallel evolution of a plate-like sternum.

Some of the postcranial bones and mandible segments of Horopeta umarere (OU 21982) spread out in the lab after removal from the main jacket.

Cheng-Hsiu Tsai examining the postcranial bones of Horopeta umarere on the big wooden table in the Otago Geology museum. This famous wooden table has been there for over a century and serves as a place to lay out big specimens, a space for photography, dissections of smallish cetaceans, and tea time in winter when it's too chilly to take afternoon tea on the steps outside (or, raining). Photo taken by me.

The holotype earbones of Horopeta umarere: it really, really looks like Mauicetus parki, and in many regards, the earbones are a mishmash of archaic features you might expect in an eomysticetid and derived features you would see in a middle Miocene "kelloggithere" like Parietobalaena. From Tsai and Fordyce (2015).

The holotype braincase fragment of Whakakai waipata: a very flat skull, but still poorly telescoped, somewhat more derived than eomysticetids. From Tsai and Fordyce (2016).

The deeply unusual earbones of Whakakai waipata: the periotic is just massive, generally looking like a hyperinflated eomysticetid periotic. The bulla is nearly indistinguishable from Horopeta and Mauicetus. From Tsai and Fordyce (2016).

Tsai's whales - Whakakai waipati and Toipahautea waitaki

These whales have no common name, and since both were from chapters of Cheng-Hsiu Tsai's thesis, I've always just called them "Tsai's whales". These are two very unusual species, mostly diagnosed from their earbones. They are similar to an unpublished gigantic mysticete from the Kokoamu Greensand that is not yet named, but called the "chocolate whale" - generally resembling a gigantic eomysticetid, though with quite different-looking earbones. We don't yet have a complete skull of one of these things, but I expect study of the "chocolate whale" to reveal an eomysticetid-like morphology. The earbones include a tympanic bulla that is somewhat more like Mauicetus and Horopeta, but unusual periotics that are massively inflated with unfused posterior processes, quite unlike anything else known from the early fossil record of mysticetes. Whahakai waipata (pronounced "fah-caw-kye"; "Wh" in the southern Maori dialect is an "f" sound, see the pronunciation guide in part 1) was named by Tsai and Fordyce (2016) and has a partial braincase, and the top of the skull is a bit flat relative to eomysticetids, and seems to lack a clear sagittal crest - and has an intertemporal constriction that is somewhat shorter than eomysticetids. The periotic, in many regards, looks like an eomysticetid periotic that has been inflated like a balloon - and it's not inconceivable that, with the description and coding of more specimens, these might form a clade with eomysticetids based on some of the earbone features.

The "chocolate whale" on display at the Otago Museum: perhaps the largest fossil cetacean skeleton that Ewan excavated from New Zealand. The skull block of Tokarahia was larger than the individual blocks here, but Tokarahia is a smaller whale; this thing is like four meters across from the lumbars to the rostrum. This was originally intended to be part of Tsai's thesis, but did not make it in there. This whale is something similar to Whakakai, and also bears some similarities to eomysticetids. Some aspects of the skull also remind me of Llanocetus, though it is certifiably a toothless mysticete. Photo taken by me.

The skull of the "chocolate whale", here looking a little less chocolate-y owing to overexposure from my flash. This skull is nearly a meter wide. Photo by me.

The excavation site and preparation of Toipahautea waitaki: in the upper left you can see Ewan posing with the weathered remains of the excavation pit, during the same field trip I posted photos of in part 1. The excavation hole for the "chocolate whale" is about 20 feet to the right, and the pit for Horopeta is about 100 feet to the left (just beyond the quarry equipment in the bottom photo).

The holotype skull and earbones of Toipahautea waitaki - at an early stage this was thought to perhaps be another Oligocene balaenoid, owing to the very steep occipital shield, which, admittedly, is vertical. However, phylogenetic analysis did not bear this out, and Toipahautea ended up being recovered as a Mauicetus/Horopeta-grade whale. From Tsai and Fordyce (2018).

Phylogenetic analyses of these whales from Tsai and Fordyce (2018). All analyses I'm aware of, including those conducted using my matrix and Felix Marx's matrix, show these whales as occurring between eomysticetids and Crown Mysticeti - indicating that these are likely to be the whales that crown mysticetes evolved directly from.

Two years later, Tsai and Fordyce (2018) named Toipahautea waitaki based on a slightly more complete specimen that preserves much of the base of the rostrum, parts of the braincase, periotic, bulla, mandible fragments, neck vertebrae, and scapula. Like eomysticetids, the nasal bones are long, the supraorbital process of the frontal is long and bears a large orbit, and the rostrum itself is quite wide - though we don't know how long. The braincase is poorly preserved, but the occipital shield seems to be vertical - resembling right whales - though the shield likely curved anteriorly. Like eomysticetids, the joint for the mandible is very large and shallow. The periotic is somewhat similar to Whakakai, but also shares some similarities with Horopeta.

Comparison of fossil cetaceans: Zygorhiza (A), Agorophius pygmaeus (B), "Mauicetus" lophocephalus (C) and Aglaocetus moreni (D). From Marples (1956).

Mauicetus or mistaken identity? New Zealand Eomysticetidae

In the 1980s and 1990s Ewan Fordyce excavated a number of skulls he recognized were similar to Mauicetus lophocephalus, but was not quite close to naming yet. Sadly, fossils from the Oligocene Chandler Bridge Formation of South Carolina, USA, were discovered and named Eomysticetus by Al Sanders and Larry Barnes in 2002. Ewan quickly realized that this collection of about a half dozen skulls from New Zealand represented eomysticetids, and likely several genera; this family was basically defined by the relatively primitive features outlined above: long nasal bones, long, non-telescoped intertemporal constriction, large temporal fossae, long zygomatic processes, and archaeocete-like earbones. In 2006 Ewan presented these specimens in an oral presentation at the Society of Vertebrate Paleontology meeting in Ottawa, Canada, during a symposium on the Origin of Neoceti - my second SVP meeting. I was wowed by the number of specimens, excellent preservation, and the diversity - they appeared to represent at least 3-4 species. The following year I dug up and prepared a specimen of the much younger baleen whale Herpetocetus from the Purisima Formation in Santa Cruz, California, and presented it at the 2008 SVP in Cleveland, Ohio - after which, Ewan approached me and asked if I was applying to doctoral programs yet. "Not yet! I'm only two months into my master's program!" I exclaimed. "Well, when the time comes, keep New Zealand in mind." I did, and three years later I was accepted into the doctoral program with a scholarship; Sarah and I flew down to Dunedin in March 2012, and I started my work on these specimens. At first there wasn't room to bring out all the skulls for side-by-side comparison, so Ewan encouraged me - in the rare chances we had to chat during my first few months, given that he had around 12 doctoral, master's, and P.G. Dip. Sci. students - to first look at all of the periotics and bullae. Each of the new skulls had at least one periotic and one bulla associated with it. My goal was not only to figure out 1) how many genera and species were present amongst the new specimens, but 2) which might be the same species, or same genus, as the species named by Marples (only Mauicetus lophocephalus and Mauicetus waitakiensis were considered to be eomysticetids; Mauicetus brevicollis is something much closer to Mauicetus parki); 3) determine whether any of these species belonged in the same genus or if they were 'monospecific', and 4) to determine whether any of these were assignable to an existing genus/species from elsewhere (e.g. Eomysticetus, Micromysticetus, Yamatocetus). After a couple of weeks acquainting myself with these specimens and poring over the earbone anatomy of basilosaurid whales and toothed mysticetes, I finally got some clarity and made some predictions about what skulls might be conspecific and which ones were not.

Excavation of Waharoa specimens: the "earthquakes" specimen (holotype), A; the springside cleft juvenile (OU 22075, shown in B in following image), B; and the Hakataramea quarry juvenile/paratype specimen (OU 22163, shown in C in the following image), C.

The full collection of fossil eomysticetids from New Zealand, collected by Ewan Fordyce and colleagues, along with the earbones of "Mauicetus" lophocephalus. From Boessenecker and Richards (2024).

Sadly, one development hampered my research somewhat. Sometime in the late 1950s, and prior to 1962, the Zoology Department moved buildings on Otago campus and the paleontology collections were transferred to the Otago Museum just across Cumberland street from campus. While the earbones, vertebrae, and mandible of Mauicetus lophocephalus were transferred and survive to this day, the skull - embedded in a large block of plaster - was lost, presumably discarded by university maintenance staff during the move. Ewan thought that the skull probably would have looked like a large rock on the floor, and staff may not have spoken to anyone in Zoology with direct knowledge of the specimen. Who knows what other rocks had been earmarked for the rubbish skip (=dumpster for my American readers); the skull is probably sitting in the landfill in Burnside, just south of town.

The full collection of eomysticetid earbones I had at my disposal during my Ph.D. Every single holotype specimen is in here, and each and every one of these specimens is now published.

The excavation of OU 22235, the "Island cliff" eomysticetid, aka "big scapula" mysticete, now the Tokarahia kauaeroa holotype - this hole was quite spectacular nearly 20 years later, and I'm pissed I didn't get a photograph of it. From Boessenecker and Fordyce (2015c).

Ewan posing for scale with our cast of the Tokarahia kauaeroa holotype slab (OU 22235).

The holotype skull block of Tokarahia kauaeroa as prepared. This block is huge and very difficult to move; because I couldn't get far enough away from the specimen to photograph it in one shot, I decided to photogrammetize the entire thing, and make a 3D model. This is actually the 3d model. From Boessenecker and Fordyce (2015c).

The evolution of the mysticete skeleton, skull, and tympanic bulla. From Boessenecker and Fordyce (2015c).

In the end, I came to the conclusion that there were six species present in four genera. Neither Mauicetus lophocephalus nor Mauicetus waitakiensis were assignable to Mauicetus, which likely belongs in a completely different (but as yet unnamed) family - and these species were instead identifiable as eomysticetids. The Island Cliff eomysticetid, OU 22235, was the largest single fossil that Ewan had ever excavated, and left in its 500 lb plaster jacket and prepared in relief. The tympanic bulla of this was quite similar to Mauicetus lophocephalus, and this specimen was named Tokarahia kauaeroa (Tokarahia, after Tokarahi - the Maori name for the mesa called "Island Cliff" by white settlers, and kauaroa meaning long jaw) in one of my thesis papers (Boessenecker and Fordyce, 2015c); we transferred Marples' species, with the new combination Tokarahia lophocephalus. One specimen of Tokarahia produced a putative tooth - these mysticetes were initially assumed to be toothless, and this discovery suggested that eomysticetids represented an intermediate stage between the toothed and baleen-bearing aetiocetid toothed mysticetes, and the completely toothless mysticetes of the Miocene and onward. Tokarahia, along with Waharoa (see below), suggest an intermediate stage with vestigial, functionless teeth along with baleen.

The holotype skull of Tohoraata raekohao in dorsal, ventral, and lateral view, along with a reconstruction of the skull, and the holotype braincase fragment (occiput) of Tohoraata waitakiensis (upper right). From Boessenecker and Fordyce (2015b).

The holotype periotic of Tohoraata raekohao and a diagram of the auditory region. From Boessenecker and Fordyce (2015b).

The holotype tympanic bulla of Tohoraata raekohao (left) and Tohoraata waitakiensis (right). From Boessenecker and Fordyce (2015b).

A much more partially preserved specimen consisting of a very big baby (well, juvenile) skull with distinctive earbones, known as the Harvey Farm whale, was named Tohoraata raekohao - tohoraata meaning 'dawn whale' and raekohao meaning 'forehead holes', referring to the distinctive foramina in the frontal bones. The short bullae with triangular outlines matched those of Mauicetus waitakiensis, so we recombined Marple's second eomysticetid as Tohoraata waitakiensis.

The Earthquakes eomysticetid - the holotype skull of Waharoa ruwhenua. From Boessenecker and Fordyce (2015a).

Juvenile eomysticetids - the juvenile paratype skull of Waharoa ruwhenua (left), the perinatal/young juvenile (referred skull, not a paraype) on the upper right, and the holotype perotic of Waharoa. From Boessenecker and Fordyce (2015a).

Were eomysticetids the last toothed mysticetes? Juveniles and adults of Waharoa have three suspicisously tooth socket-looking foramina in their premaxilla, which suspiciously also houses three teeth in most placental mammals (and all toothed mysticetes and archaeocetes). There are additionally similar structures in the tips of the mandibles. Are these alveoli? We cautiously interpreted them as possible alveoli. From Boessenecker and Fordyce (2015a).

Growth changes in Waharoa ruwhenua. On the left are histological samples taken from the ribs of the young juvenile (OU 22075), older juvenile (OU 22163), and the adult holotype (OU 22044); woven bone is present in the juveniles, confirming juvenile status, and there is highly remodeled haversian bone present in the holotype, confirming adult status. This is not as accurate as counting LAGS (lines of arrested growth), but is useful as a general rule of thumb: baby, subadult, or mature adult - in a relative framework. On the right, the earbones of Waharoa change: the tympanic bulla actually grows somewhat, unlike modern mysticetes where they do not grow after birth. In the periotic, the hole for the facial nerve increases in diameter, perhaps corresponding to the increase in length of the palate, jaws, and the tongue - which the facial nerve innervates. From Boessenecker and Fordyce (2015a).

More on growth in Waharoa: the rostrum lengthens considerably during postnatal (e.g. after birth) growth in eomysticetids. Modern balaenopterid whales have long snouts, but they're nearly the same proportion at birth. Eomysticetids have a considerably steeper rate of rostral growth relative to other mysticetes. This strongly suggests that the length of the rostrum is critical in feeding, and the process of acceleration is likely responsible, but to a greater degree than in balaenopterid whales. From Boessenecker and Fordyce (2015a).

Two other genera were uncovered by Fordyce's field work that were completely undetected by Marples' efforts. One of these new taxa consisted of three skulls - the "Earthquakes" eomysticetid, the Haugh's quarry eomysticetid, and the "Springside cleft" juvenile mysticete - a species somewhat more delicately built than Tokarahia or Tohoraata, with smaller earbones and a narrower skull. We named this Waharoa ruwhenua - the species name here is a bit of word play. The fossil locality is called "The Earthquakes", since the way the rocks of the Otekaike Limestone have been exposed and weathered, it looks like a cartoon rift in the ground. Ruwhenua in Maori translates to "shaking land" - the Maori word for an earthquake. Waharoa means 'long mouth', referring to the exceedingly long palate and mandible of the main specimen. Specimens of Waharoa provide some insights into the feeding morphology and growth of eomysticetids, and early mysticetes in general. There are some tooth socket like structures in two of the specimens, suggesting a handful of vestigial peg-like teeth, as potentially preserved in Tokarahia. The palate has a number of palatal foramina, strongly suggesting the presence of baleen. However, these foramina are not present at the very front of the mouth, suggesting a gap in the baleen and perhaps a skim feeding behavior like modern right whales. The growth series of Waharoa ruwhenua includes a perinatal individual likely only a few months old at the very most, a somewhat larger juvenile, and an adult - confirmed through bone histology. The growth series indicates that the rostrum and palate grow rapidly during growth, and that juveniles are born with relatively shorter snouts, with the snout growing much more rapidly than in any modern mysticete. Similarly, one of the various holes in the earbones - the canal for the facial nerve - increases in diameter during growth. The facial nerve innervates the tongue, so it's possible that the nerve increases in diameter to innervate a much larger tongue in later life.

The highly bioeroded skull of the Waihao river eomysticetid - the holotype of Matapanui waihao. Note how the middle section of the right mandible was bioeroded away, but each end stayed in its approximate location; the braincase, and posterior end of the left mandible, were reoriented by currents after considerable bioerosion by bone eating worms (Osedax). From Boessenecker and Fordyce (2017a).

The well-preserved right periotic of Matapanui waihao. The left one was accidentally sawn through with a masonry saw during the excavation. "C'est la vie" Ewan said, when he shared that with me. From Boessenecker and Fordyce (2017a).

The left tympanic bulla of Matapanui waihao, with the posterior process in articulation (held in place with clay). From Boessenecker and Fordyce (2017a).

The last eomysticetid from my thesis was Matapanui waihao - originally named Matapa waihao, but the genus name was preoccupied by a genus of butterflies from Sri Lanka. So, we quickly renamed it Matapanui - translating to "big flat face" in Maori (Boessenecker and Fordyce, 2017c). The species name is after the Waihao river where it was collected (NOT the Waihao greensand!). This species was based off of specimens from the Kokoamu Greensand, and the type specimen is the oldest eomysticetid from New Zealand, dating to the Whaingaroan stage - approximately 28-27 Ma, though only 1-2 million years older than Tokarahia and Tohoraata. Matapanui has a somewhat longer and more 'square' supraorbital process of the frontal that is dorsally quite flat, and a curved rather than pointed apex of the occipital shield. The earbones are quite distinctive, with a proportionally large 'cochlea' (to be specific, the cochlear portion of the periotic). Several specimens were collected in parallel, including a fragmentary specimen from Sisters Creek consisting of a skull fragment, periotic, and partial atlas vertebra, and a partial braincase of a much more mature individual with fragmentary periotic from either the Potikohua Limestone or the Tiropahi Limestone from an underground limestone exposure in Te Tahi Cave on the west coast of the South Island, with poor age control. One of Ewan's students reported the specimen embedded in the side of the cave, and Ewan went spelunking - and wrapped up the braincase in his coat. Based on this fragmentary specimen, Matapanui was likely the largest and most robust of all of the NZ eomysticetids.

A fragmentary juvenile eomysticetid with a distinctive mandible: the end is blocky and curved dorsally, two traits otherwise known only in Yamatocetus from Japan. We proposed that this specimen from the Otekaike Limestone indicated that Yamatocetus had an antitropical distribution in the western Pacific. From Boessenecker and Fordyce (2017b).

The semi-controversial specimen OU 22744 from the "Protula bed" of the uppermost Otekaike Limestone at Hakataramea quarry, which we identified as cf. Waharoa based on the morphology of the atlas vertebra. From Boessenecker and Fordyce (2017b).

Ewan and I reported a couple more eomysticetids in a rather short paper published in 2017. This final paper from my Ph.D. research reported a tentatively identified specimen of Yamatocetus from New Zealand, consisting of a fragmentary braincase associated with distinctive mandibles. The anterior tips of the mandibles were squared, unlike the spear-shaped profile of Tokarahia, Waharoa, and probably Matapanui, and also dorsally curved at their anterior tips - a combination of features only known in the Japanese eomysticetid Yamatocetus canaliculatus. This specimen suggests that Yamatocetus had an antitropical distribution in the western Pacific - e.g. living in both the northern and southern parts of the western Pacific, and likely the only eomysticetid with an antitropical distribution at the genus level. The second specimen was tentatively identified as Waharoa based on the similar morphology of the atlas vertebra, and is a relatively fragmentary postcranial skeleton from near the top of the Otekaike Limestone; we identified the specimen as cf. Waharoa, and owing to its stratigraphic position, it is the only eomysticetid that appears to have dated to the earliest Miocene; indeed, the horizon the specimen is from a horizon dated to 22.8-22.3 Ma, but that has recently been revised (see below). A review paper on the fossil record of New Zealand Eomysticetidae was published by Marcus Richards and I (2024) in the Fossil Vertebrates from Zealandia special volume of the Journal of the Royal Society of New Zealand, wherein we briefly summarize what we know and what the major contributions of the fossil assemblage were, in addition to figuring a couple of recently discovered (and rediscovered) specimens.

Revised Geochronology of latest Oligocene mysticetes from the Otekaike Limestone

A new study by Felix Marx et al. (2024) published in the same special volume of the JRSNZ on fossil vertebrates from Zealandia provides a slate of new Strontium isotope dates for sixteen of the mysticete (and some odontocete) specimens from the Otekaike Limestone. Strontium isotopes have varied naturally in seawater since the Cambrian, with the curve going up and down - and the curve, specifically, being formed by the ratio of Strontium 87 and 86. Both are stable isotopes (e.g. they don't undergo radioactive decay, though 87Sr is radiogenic in origin, decaying from Rubidium 87). Differences in what rocks are weathering out at the earth's surface result in changes to the ratio of 87Sr versus 86Sr, with peaks and valleys through time, but generally since the Cretaceous getting more enriched in 87Sr. In many periods of earth's history, (especially the Cenozoic) the line is steep enough that if you get a new ratio, you can get quite a good date from it - in this study, and thanks to the steepness of the curve during the Oligocene, the error can be as small as +/- 100,000-200,000 years. But, you need relatively robust, unaltered marine invertebrate shells to grind down into a powder and analyzed with an X-ray diffractor. For this study, they used Lentipecten shells - relatively robust scallop shells measuring up to about 1-2 mm in thickness and about 7-9 cm across. At Haugh's quarry, these would sometimes pop out of the limestone free of matrix, and we would unceremoniously throw these at each other like frisbees. Ewan Fordyce had a habit of keeping matrix and associated invertebrates found during the excavation and preparation of fossil cetaceans, and in this case, permitted quite a few specimens to be dated isotopically.

The record of eomysticetids and Mauicetus-Horopeta grade mysticetes from New Zealand and beyond: New Zealand has some of the only known fossil mysticetes from the earliest Miocene, making the collection at Otago one of the globally most important for studying this "dark age" in mysticete evolution. From Marx et al. (2024).

All sampled eomysticetids from the Otekaike Limestone, save one (keep reading) were found to be squarely in the Oligocene, with ages of around 25-24 Ma - slightly younger than originally considered, as some of these were thought to be Duntroonian in age, which is about 27-25 Ma; most of these all seem to be Waitakian (25-23 Ma) instead. As for the specimen that Ewan and I reported that we considered, at the time, to be an earliest Miocene eomysticetid? Marx et al. (2024) think that that specimen is actually some sort of Mauicetus-like mysticete. We were appropriately circumspect about the identification of that specimen as cf. Waharoa, based chiefly on the atlas morphology - but more recently collected Mauicetus-like specimens, including a monolith of a jacket we excavated in 2013, preserve similarly humongous, robust atlases that challenge our identification. Further, if the specimen does turn out to be an eomysticetid, the date on the specimen is somewhat older than we initially thought based on its stratigraphic position relative to the "Protula Bed" in Haugh's quarry, which suggested it was about a meter into the Miocene - instead, the date is 23.08 Ma, just slightly older than the Oligocene-Miocene boundary at 23.03 (though perhaps splitting hairs here, given that the error on this measurement is +/- 0.5 million years).

In sum, this study clarifies that there does seem to be an absence of eomysticetids from the uppermost part of the Otekaike Limestone; the upper ten or 15 meters, generally representing strata immediately at/around the Oligocene-Miocene boundary, appear to only represent Mauicetus-like taxa. There don't appear to be any of the strange mysticetes like "Tsai's whales" - e.g. Horopeta, Whakakai, and Toipahautea - most of these are from the Kokoamu Greensand, or near the base of the Otekaike Limestone. This study also raises the possibility that a couple of the marker beds we've used to identify the base of the Duntroonian might be slightly younger than originally thought, or that the Otekaike Limestone is time-transgressive. Most critically, is that it apparently demonstrates the extinction of the Eomysticetidae just before the Oligocene-Miocene boundary, leading into the Aquitanian baleen whale gap, documented well a few years earlier by Marx et al. (2019).

New Zealand fossil mysticetes and the origin of Crown Mysticeti

One thing is certain - New Zealand boasts, by a very wide margin, the greatest diversity of toothless/baleen-bearing mysticetes in the world during the Oligocene epoch. There are to date approximately six eomysticetids, three of "Tsai's whales" (and at least 1-2 additional unnamed species), Mauicetus parki, the ZMT 67 taxon (either Mauicetus or a closely related genus), a possible balaenoid represented by specimen OU 22224, and likely a couple of others - ballpark, around 12-15 species for the late Oligocene (Chattian stage; e.g. Duntroonian to Waitakian) and earliest Miocene (e.g. ZMT 67 is from the first million years of the early Miocene Aquitanian stage) alone. This sort of diversity is absurd - and, while not all of these species are present at the same horizon, at least half of them are if one takes a look at the Kokoamu Greensand, for example. Further to the point, according to the careful work of Marx et al. (2023), the eomysticetids tend to be lower down stratigraphically and do not temporally overlap with true Mauicetus-type fossils, suggesting some faunal change within the region. In addition to the sheer diversity, New Zealand also boasts the majority of the entire fossil record of Oligocene baleen-bearing mysticetes; there are between fifteen and twenty eomysticetid skulls from Japan, Washington, Oregon, Baja California, South Carolina, and Europe - combined - and at least that many eomysticetid skulls from New Zealand, plus at least that approximate number of whales in the Mauicetus and "Tsai's whales" grade. I would wager that New Zealand boasts something like half or two thirds of the fossil record of Oligocene chaeomysticetes.

The referred juvenile skull of Mauicetus parki - this specimen revealed a far more derived looking skull than Benham ever anticipated, and certainly one that would not have surprised Kellogg, for it greatly resembles Parietobalaena - but is much, much older (~23 Ma v. 16 Ma). From Tsai (2024).

A review paper by my PhD colleague and dear friend Cheng-Hsiu Tsai (2023) in the same special volume of the JRSNZ considers this to be likely evidence that crown Mysticeti - the group formed by modern baleen whales and their most recent common ancestor - likely evolved in the southern hemisphere. Tsai points out that whales in the Topiahautea-Whakakai-Horopeta complex (which I've informally called "Tsai's whales" in this blog post) have, so far, really only been found in New Zealand, and further suggests that niche partitioning was likely in effect to permit this unusual degree of diversity. Further to the point, 'toothless' mysticete "assemblages" from the North Pacific and North Atlantic tend to consist of only a single species of eomysticetid: Sitsqwayk and Maiabalaena are both from the Pacific Northwest, but are from different stratigraphic units and not contemporaneous; Yamatocetus is the only 'toothless' mysticete from the Ashiya Group of Japan; and Eomysticetus and Micromysticetus are both found in Charleston, South Carolina, but are found in the Chandler Bridge Formation and underlying Ashley Formation (respectively) and separated in time by about ~4-5 million years. Charleston rivals New Zealand for Oligocene cetacean sampling - and certainly suprasses it in terms of the odontocete assemblage, perhaps three or fourfold (there are between 50 and 80 skulls, versus perhaps one or two dozen from NZ) - but there are only about a half dozen quasi-complete 'toothless' mysticete skulls that have ever been found in Charleston (as opposed to many, many dozens of odontocetes) and they are all eomysticetids (save one, see below).

The skull of Tlaxcallicetus from the Oligocene of Baja California. From Hernandez-Cisneros (2018).

There are a few tantalizing possibilities of "Tsai's whales" being found elsewhere: I strongly suspect that Tlaxcallicetus, named by our Mexican colleague Ehecatl Hernandez-Cisneros a few years ago, may be one of these whales; the periotic is quite strange. There's a fragmentary periotic in a squamosal chunk I acid prepared from the Pysht Formation that looks like Whakakai, and is clearly not an eomysticetid, but it is in bad shape. And lastly, there is a Horopeta-like juvenile braincase I excavated from the ~30 myo Ashley Formation in South Carolina back in 2018 or so, and it remains unstudied. But, these are unconfirmed identifications and I don't put much stock in them for the time being. Even if these are accepted, they barely inflate diversity elsewhere (raising the number to 2 or perhaps 3 baleen-bearing mysticetes) and likely represent diversity 'exported' from the south. Tsai (2023) contrasts these whales, which he terms the Toipahautea-Mauicetus grade, with eomysticetids by highlighting that eomysticetids likely diversified earlier in the Oligocene, having already dispersed to all corners of the globe by the mid Oligocene. On the other hand, "Tsai's whales" and Mauicetus are found only locally, and again, are surprisingly diverse - suggesting that the NZ fossil record is preserving an 'in situ' radiation. He concludes that

One last study requires discussion, and this is analysis of the "baleen whale gap" reported by Marx et al. (2019). This study examined a wide sampling of baleen whale earbones from the Oligocene and early Miocene of New Zealand and Australia, including toothed mysticetes, along with global trends in Oligo-Miocene mysticete diversity. They found that in the more coastal deposits of Australia, the fossil record of mysticetes were dominated by small toothed mysticetes in the Mammalodontidae, which made up about 82% of the fossils altogether; 15% were eomysticetids, and only 3% were non-eomysticetid true mysticetes - e.g. Mauicetus-like species of possible records of "Tsai's whales". In New Zealand, which they considered to represent more pelagic conditions given the near-submergence of Zealandia (see first post) and the remoteness of the Zealandia shelf, the fossil assemblage is instead dominated by baleen-bearing mysticetes with non-eomysticetid mysticetes comprising a staggering 73% of the assemblage, mammalodontids only about 4%, and eomysticetids at 23% of the fauna.

Comparison of mysticete assemblages from the Oligocene of Australia (A1, B1) and New Zealand (A2, B2). Eomysticetids are similarly uncommon in both regions, but the real difference lies in toothed mysticetes and "Tsai's whales" - aka "other Chaeomysticeti" here. The former - mammalodontids - dominate the Australian record, whereas they are very rare in New Zealand, which is dominated by these "other Chaeomysticeti" - mostly members of the Mauicetus-Horopeta grade, aka "Tsai's whales" elsewhere in this post. From Marx et al. (2019).

Marx et al. (2019) infer a 'dark age', or as I call it, a baleen whale gap during the first five million years of the Miocene. We know they clearly survived, but baleen whale fossils are astonishingly rare during the Aquitanian stage and earliest Burdigalian, only becoming common again around 17-18 mya. All early Miocene mysticetes known from the Aquitanian are relatively derived species that some of us have informally called "Kelloggitheres" - also slightly less informally referred to as "cetotheres" sensu lato, stem balaenopteroids, or stem thalassotheres. I'll keep using "Kelloggitheres" as the term was devised in an SVP talk years ago by Erich Fitzgerald, in honor of Remington Kellogg, who worked on a ton of these sorts of whales from the Miocene of Maryland/Virginia, California, South America, and Oregon; these are species like the well-known Parietobalaena and Diorocetus from the Calvert Formation of Maryland. Mauicetus parki in particular shares a lot in common with these, differing chiefly in having a somewhat more archaic set of earbones and vertex, and I would argue, is the first "Kelloggithere". One thing I've noticed is that these species are all remarkably similar, and given that aside from the early right whale Morenocetus, virtually all early Miocene mysticetes have "Kelloggithere" affinities, these species are probably extremely oversplit and are in dire need of revision. As a result of this, anatomical diversity - a metric frequently called 'disparity' - tanks during the early Miocene, reflecting the fact that these are all very similar looking whales with very slight variations on a theme.

What explains the extinction of toothed mysticetes and eomysticetids at the end of the Oligocene, and the ensuing global rarity of crown mysticetes during the Aquitanian stage (earliest Miocene, 23-20 Ma)? Marx et al. (2019) suggest that a cooling event may have resulted in a temporary collapse of shallow marine food webs. The "other Chaeomysticeti" during the Oligocene are really only known from New Zealand, which they hypothesize to mean that these whales were much more pelagic, explaining their absence from Australia. Later, pelagic mysticetes would end up diversifying and once again be found as fossils in shallow marine environments starting in the Burdigalian stage (late early Miocene, ~17-20 Ma). From Marx et al. (2019).

Marx et al. (2019) correlate the extinction of toothed mysticetes and eomysticetids with a brief but drastic cooling period coinciding with a drop in sea level at the end of the Oligocene, which may have driven faunal collapse in coastal marine settings, leading to the extinction of decidedly shallow marine toothed mysticetes like the mammalodontids. Likewise, there was a crash in global diatom abundance in the earliest Miocene, which may have led to globally reduced biomass of zooplankton. They hypothesized that the whales which seemed to have survived are those from New Zealand with a more pelagic (open ocean) habitus - perhaps explaining their rarity in continental shelf deposits elsewhere for several million years. During this 'dark age', baleen whales were possibly pelagic only and likely to be numerically quite rare - only diversifying once again as climate, primary productivity, and planktonic diversity all increased during the Middle Miocene Climatic Optimum around 15 mya. Curiously, there is a potential early Miocene extinction event recorded in pelagic shark fossils around 18 mya by Elizabeth Sibert and colleagues (2021; covered in an earlier blog post, read it here), and Tsai (2024) suggests that this may be related to the baleen whale 'dark age'. I am tempted to agree, though the baleen whale record tanks several million years prior.

As always, there is more yet to do: all of these jackets in the University of Otago basement contain fossil cetaceans, chiefly from the upper Otekaike Limestone at Hakataramea Quarry (and are therefore about 22-25 Ma), and few have been prepared. Each one potentially represents a future holotype or a referred specimen of an existing species that might shed critical light on the functional anatomy and evolution of the earliest crown mysticetes. From Tsai (2023).

Cheng-Hsiu Tsai in the final stages of his Ph.D. research in late 2014, with dozens of fossil (and modern) mysticete earbones. The specimens in the foreground are mostly eomysticetids he had borrowed from my office, since I was largely done with describing and photographing them at this stage. Photo by me.

Regardless, we have a lot more to learn - even just from the collections of the University of Otago. Tsai (2024) points out that many of these early mysticetes are known within the Fordyce lab, past and present - but formally, many such specimens are only known as a trail of breadcrumbs in SVP abstracts and mentions in various papers. One such specimen is the "Oligocene right whale", OU 22224 - a mysticete close to the ancestry of Crown Mysticeti. This specimen has a vertical occipital shield and an arched rostrum - resulting in its identification as a possible Oligocene balaenid. If the identification holds, it would be the oldest known crown mysticete, and certainly the oldest member of any modern family. However, it frequently plots out amongst "Tsai's whales" - within the Toipahautea-Mauicetus complex, though in the most recent phylogeny by Tsai and Fordyce (2018), it did plot out as a sister taxon to the Balaenidae. We'll have to await study of the specimen - but aside from this, there are many other unpublished mysticetes known from partial braincases, fragmentary skulls, nearly complete skulls, and most that have been excavated in recent years seem to be Mauicetus-like whales. Recently, for example, the enormous, nearly 3 meter long jacket we nicknamed the "star destroyer" has been prepared and photos shared with me; it looks to be a large whale close to Mauicetus and ZMT 67 in its morphology. There are untold treasures awaiting study in the Otago collection - Fordyce's collecting over the past 40 years will keep us busy for decades.

Some new specimens preliminarily reported in my paper with Marcus Richards earlier this year: A new specimen of Tokarahia (C-D) and Matapanui (I), along with the identification of a partial skull (E-G) that is probably associated with a Matapanui waihao periotic (H) that were separated many years prior to my arrival in New Zealand, with the specimen sheets misplaced. This new rostrum of Matapanui (E-G) has some of the most finely preserved palatal foramina present in any eomysticetid, clearly indicating that eomysticetids in general had baleen. From Boessenecker and Richards (2024).

Three new eomysticetid specimens have either been freshly prepared or were collected entirely after my time at Otago. The first is OU 22473, the periotic of which I had described in 2017 as a specimen of Matapanui waihao. A partial skull (OU 22120) was possibly associated - however, the periotic was separated from the skull after preparation by the late preparator Andrew Grebneff and for a long while it was unclear if the partial skull really belonged. Ewan recalled a white periotic being associated with the block, and this unlabeled specimen seemed to fit the bill - as the only good candidate, we always assumed they were the same specimen. However, short of being able to demonstrate it, we cautiously assigned a new number for the periotic. A while after I left, preparator Sophie White conducted some more preparation of the skull - the skull was in a block of limestone that cracked horizontally right through the rostrum. On one block is the supraorbital process, one mandible, and the base of the rostrum, with the dorsal surface prepped out; on the other block is the ventral surface of the rest of the rostrum. While not prepared completely, the new prepwork showcases the palatal foramina quite beautifully - clearly demonstrating that eomysticetids, when well-preserved, do indeed have an extensive network of vascular channels for the arteries and nerves that feed the baleen. Likewise, it means that if specimens like the holotype skull of Maiabalaena - once championed as evidence that eomysticetids had neither baleen nor teeth - were better preserved, they would likely show something similar. But, you really do need specimens with well-preserved (and well-prepared) palates to make such claims. The other two specimens are more fragmentary. One, OU 22783, is a partial skull with periotic of Tokarahia; it preserves a partial rostrum, posterior mandible, and braincase. The other is the Smite River whale, OU 22028, is another specimen of Matapanui sp., with an even more fragmentary mandible, braincase, and partial periotic. These specimens have been figured and briefly outlined, but I'll have to make it back down to Dunedin sometime to get these specimens written up!

On that note, onto part three - fossil odontocetes from New Zealand, Ewan's true passion.

References

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Fordyce, R. E., & Hiller, N. (2014). An associated skeleton of juvenile late Eocene basilosaurid archaeocete from New Zealand. Journal of Vertebrate Paleontology, 34, 131A.

Fordyce, R. E., & Marx, F. G. (2016). Mysticetes baring their teeth: a new fossil whale, Mammalodon hakataramea, from the southwest Pacific. Memoirs of Museum Victoria, 74, 107-116.

Glaessner, M. F. (1972). Redescription of the tooth of an Oligocene whale from North Canterbury, New Zealand. Records of the Canterbury Museum, 9, 183-187.

Hector, J. (1881). Notes on New Zealand Cetacea, recent and fossil. Transactions of the New Zealand Institute, 13, 434-436.

Kellogg, R. (1936). A review of the Archaeoceti. Carnegie Institution of Washington Publication, 482, 1-366.

Keyes, I. W. (1973). Early Oligocene squalodont cetacean from Oamaru, New Zealand. New Zealand Journal of Marine and Freshwater Research, 7, 381-390.

Köhler, R., & Fordyce, R. E. (1997). An archaeocete whale (Cetacea: Archaeoceti) from the Eocene Waihao Greensand, New Zealand. Journal of Vertebrate Paleontology, 17, 574-583.

Marples, B. J. (1956). Cetotheres (Cetacea) from the Oligocene of New Zealand. Proceedings of the Zoological Society of London, 126, 565-580.

Marx, F. G., Coste, A., Richards, M. D., Palin, J. M., & Fordyce, R. E. (2024). Strontium isotopes reveal a globally unique assemblage of early Miocene baleen whales. Journal of the Royal Society of New Zealand, 54, 711-721.

Marx, F. G., Fitzgerald, E. M. G., & Fordyce, R. E. (2019). Like phoenix from the ashes: how modern baleen whales arose from a fossil "dark age". Acta Palaeontologica Polonica, 64(2), 231-238.

Marx, F. G., & Fordyce, R. E. (2015). Baleen boom and bust: a synthesis of mysticete phylogeny, diversity and disparity. Royal Society Open Science, 2, 140434.

Mitchell, E. D. (1989). A new cetacean from the late Eocene Meseta Formation, Seymour Island, Antarctic Peninsula. Canadian Journal of Earth Sciences, 46, 2219-2235.

Raine, J. I., Beu, A. G., Boyes, A. F., Campbell, H. J., Cooper, R. A., Crampton, J. S., . . . Morgans, H. E. G. (2012). New Zealand Geological Timescale v.2012/1. Lower Hutt, New Zealand: GNS Science.

Thompson, N. K., Bassett, K. N., & Reid, C. M. (2014). The effect of volcanism on cool-water carbonate facies during maximum inundation of Zealandia in the Waitaki-Oamaru region. New Zealand Journal of Geology and Geophysics, 57, 149-169.

Tsai, C.-H. (2024). In search of the origin of crown Mysticeti. Journal of the Royal Society of New Zealand, 54, 682-695.

Tsai, C.-H., & Fordyce, R. E. (2015). The earliest gulp-feeding mysticete (Cetacea: Mysticeti) from the Oligocene of New Zealand. Journal of Mammalian Evolution, 22, 535-560.

Tsai, C.-H., & Fordyce, R. E. (2016). Archaic baleen whale from the Kokoamu Greensand: earbones distinguish a new late Oligocene mysticete (Cetacea: Mysticeti) from New Zealand. Journal of the Royal Society of New Zealand, 46, 117-138.

Tsai, C.-H., & Fordyce, R. E. (2018). A new archaic baleen whale Toipahautea waitaki (early Late Oligocene, New Zealand) and the origins of crown Mysticeti. Royal Society Open Science, 5(172453).

Uhen, M. D. (2013). A review of North American Basilosauridae. Alabama Museum of Natural History Bulletin, 31(2), 1-45.

The fossil record of early cetaceans from New Zealand, 1: introduction, archaeocetes, and toothed mysticetes

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

This is part 1 of the fossil record of early cetaceans of New Zealand, with an introduction to the stratigraphy and geology, and the archaeocetes and toothed mysticetes from NZ. For toothless baleen whales, see part 2 here, and for "dolphins" (Odontoceti), see part 3 here (out next Monday!).

The holotype teeth and earbones of Kekenodon onamata - one of the earliest named fossil cetaceans from New Zealand, and by far the most consistently enigmatic. From Hector (1881).

New Zealand is a special place - a rainy, lush, cold island nation in the south Pacific. A veritable lost world - when the first Polynesians arrived around 1300 CE, the island was populated by gigantic birds. When Europeans (Pakeha) first "discovered" New Zealand, the Maori oral tradition was so strong that there were still names for these - the moa - despite having been driven to extinction centuries before. The bird fauna and plant flora are still very distinctive, despite disappearance of many of the larger species. New Zealand is just the exposed portion of the landmass Zealandia - technically a microcontinent. However, it's the largest of these, and also known as the "eighth continent" owing to its size: it's half the size of Australia, and more than six times the area of the second largest 'microcontinent', Madagascar. Most of Zealandia is underwater - about 94% - yet composed of light, silica rich continental crust that just happens to be mostly submerged, forming broad swathes of shallow continental shelf that is considerably shallower than the abyssal plain surrounding it. Other well-known islands that are parts of Zealandia include the Chatham Islands east of Dunedin, Stewart Island south of Invercargill, New Caledonia, Norfolk Island, and nearly 700 additional islands in the region.

New Zealand, that part of the world frequently left off of world maps! While few are familiar with New Zealand other than "it's near Australia, I think", the lost continent of Zealandia - here outlined in pink - is even less well known to the public. All of that shallow continental shelf is continental crust, a large chunk of Pangea that rifted apart - it's about 2/3 the land area of Australia, and also includes New Caledonia. Image credit: NOAA via Wikimedia.

New Zealand has also been largely submerged for much of its history - resulting in a fantastic marine fossil record that is nearly continuous from the late Cretaceous to the Pleistocene. Part of this marine record - the Oligocene epoch - led me to move to Dunedin with my wife Sarah in 2012 and begin my Ph.D. research on fossil whales with Dr. Ewan Fordyce in the Geology Department at the University of Otago. Much of the information I'll be covering in these posts is either based on fossils discovered by Ewan or published or otherwise studied by him and his students. Sadly, Ewan passed away in November 2023. I've decided to restrict this post to the Eocene and Oligocene record of archaeocete, mysticete, and odontocete fossils from the country, and may delve *a little* into the early Miocene - the fossil record of cetaceans from the mid-late Miocene and Pliocene is much more spotty, and the real "meat" is in the "middle" Cenozoic - approximately 40-20 million years ago. Furthermore, virtually all of these fossils are from the South Island, and specifically the southern Canterbury Basin in the vicinity of Oamaru - chiefly the Waitaki Valley and the Hakataramea Valley.

Some notes on Maori (and Polynesian) pronunciation

New Zealand is notable for being the southwestern tip of the Polynesian triangle - defined as all the islands and waters between New Zealand, Hawaii, and Rapa Nui (aka Easter Island). Maori (pronounced Maw-ri - not Mow-ri, e.g. not rhyming with 'Now') is not too dissimilar from Hawaiian or Tongan, or Tahitian* for that matter. Many of the words are very similar - for example, in Maori a 'k' would be present where in Hawaiian there would be a 't' - famous Waikiki beach would become Waititi, which happens to be the last name of the critically acclaimed director Taiika Waititi (who was still very much a local phenomenon when we were there, mostly showing up in a bunch of hilarious beer commercials).

*The 'a' in many Polynesian words is typically pronounced longer than we think if we were reading English words. Tahiti and Samoa are not "tuh-heetee" or "suh-mo-uh" but "taw-hee-tee" and "saw-moe-uh". On a family trip to Oahu in 2001 I recall learning this at the Polynesian cultural center, and the memory of it jolted back into my brain after a few days in Dunedin. To alleviate this, when you're actually in New Zealand, the 'long A' is usually identified with a macron.

The Polynesian Triangle. When most folks think about Polynesia, tropical paradises like Tahiti and Hawaii come to mind - but it also includes New Zealand, which is the furthest south and the coldest climate that Polynesians colonized. 1) Hawaii; 2) Aotearoa/New Zealand; 3) Rapa Nui/Easter Island; 4) Tonga & Samoa; 5) Tahiti. Image credit: Kahuroa via Wikimedia commons.

What's really impressive is that Polynesia was settled so rapidly and efficiently that the language has barely had any time to change - the Polynesian settling of the south Pacific started around 700 AD with their arrival in the Marquesas, Cook islands, and Tahiti; by 800-900 arriving in Samoa, Hawaii, and Tonga, and around 1000-1200 Rapa Nui (Easter Island), and lastly, exploring south and settling Aotearoa (New Zealand) by 1200 (Moa became extinct by around 1450). Contact with westerners like the Dutch explorer Abel Tasman did not occur until the 17th century (though the Spanish and Portugese made contact with the peoples of Melanesia and Micronesia further to the north, e.g. Guam, during the prior century). Captain James Cook landed in Tahiti and Tupaia, a Tahitian 'priest' of sorts, befriended the chief botanist of the expedition, Joseph Banks (who would later become the most influential president of the Royal Society), and joined the expedition. His story is remarkable - trained as a star navigator, from memory, he was able to correctly map out at least 134 islands within 2000 miles and provide the names of at least 70 of them. However, the most remarkable - and relevant - part of the story here is that once arriving in New Zealand a few months later in October 1769 - over 4,000 kilometers away - Tupaia was able to speak with the Maori and have mutually intelligible conversations. Like anywhere else in Polynesia, there were of course some dialect differences, but the recent and rapid colonization of Polynesia meant that the language is surprisingly similar over vast differences - no doubt stabilized by continuous maritime trade and voyages between islands (on Tupaia's map, for example, he indicated that he had personally visited at least 13 of the islands, and that his ancestors had visited all of them, except for an island north of Fiji, and Oahu. Anyway, there's a fabulous book titled Voyagers by Nicholas Thomas that goes into the rich history of the Polynesian colonization of the Pacific.

Now, onto some pronunciation (and take this with a grain of salt as even Pakeha living in NZ for three years cannot do a great job pronouncing everything properly):

The 'r' in Maori words is typically rolled, slightly - but not so extravagantly as in Spanish.

'i' is always an 'eee' sound.

'wh' in the South Island dialect is, strangely, pronounced as an 'f' - this is likely due to a bad translation error made by Pakeha (foreigners) in the late 19th century. Because all of the fossil cetaceans from NZ are based on fossils from the South Island, the 'wh' is always pronounced as an 'f'. So - the species name for the dolphin Waipatia maerewhenua? That's 'mare-reh-fen-you-uh'. In various North Island dialects, wh sounds identical to w.

T is always hard. Waipatia might be spelled like the name of the Hellenic scholar Hypatia, but the -tia is not pronounced 'sh'.

There are a ton of dipthongs in Maori:

'ai' is pronounced like I, e.g. 'Wai' is "why".

'ae' is pronounced like 'ai' in English, e.g. the way you would pronounce 'air', 'fair', or 'hair'.

'ua' is pronounced 'you-uh'

'ui' is pronounced 'you-eee'

'oi' is 'oy', so if you

'au' is a difficult one, but sounds like 'oh'.

'ou' is pronounced more like 'ooo'.

'eo' is pronounced 'eyyy-oh'

I'm sure I've missed some, but if you're wanting to learn more, check out resources like this: https://www.maorilanguage.net/how-to-pronounce-maori/.

Now, one major wrinkle to learning Maori pronunciation is that you have to do it while learning New Zealand pronunciation of English, which is barely English. It was one thing speaking with Fordyce at conferences in the USA and Canada, despite his very distinctive accent - he knew to use American words rather than their 'kiwi' counterparts. This kindness left me more or less completely unprepared while ordering food, drinks, taxis, etc. while speaking with New Zealanders. Ironically, exposure to Tongan accents in high school and visits to Hawaii meant that I didn't find Maori accents too difficult, but good lord, it was tough understand white New Zealanders. Aside from a completely different vocabulary for every day items and activities, the vowels are all shifted: a becomes e, e becomes i, i becomes a u of all things. Fish becomes 'fush', fashion is 'feshion', flesh becomes 'flish'. Despite being close to Australia (Ewan would deliberately draw out the aaaust, like someone here making fun of a Texan accent), New Zealand pronunciation is anything but: where vowels are drawn out into the down-under version of a southern drawl ('no' has like three different vowels in it and ends in an r, like 'naaur'), in NZ the vowels are short and clipped, meaning that innocent Americans are frequently going to look confused until a waiter will give a loud, and painfully drawn out American-ized pronunciation (this happened constantly for about the first month I was down there!). If you want some more exposure to the lovely and bizarre Kiwi accent, I encourage you to watch such films as What we Do in the Shadows, The Hunt for the Wilderpeople, or the show Flight of the Conchords.

A regional geologic map of Zealandia and surrounding trenches. For non-geologists, the lines with the black teeth on them are thrust faults/subduction zones, the teeth pointing towards the overriding slab. Note how the teeth change direction from along the Kermadec trench northeast of New Zealand (oceanic crust moving west and being subducted) versus the Puysegur trench (oceanic crust on west being subducted under east). This difference in direction is largely responsible for formation of the Alpine fault, which is *mostly* a strike-slip fault, and has resulted in shearing of New Zealand. From Schellart et al. (2006).

Major Geological Events in New Zealand

Today, Zealandia is located at the southern terminus of the Tonga-Kermadec Trenches* - a subduction zone formed where the Pacific Plate is being subducted below the eastern edge of the Australian Plate. This subduction zone transitions into a transform boundary - forming one of the largest strike-slip faults in the western Pacific: the Alpine Fault. This is sort of the southwestern Pacific equivalent of the San Andreas fault. For every four meters of lateral movement, there is an additional meter of uplift - resulting in the incredibly rugged Southern Alps on the South Island. I've been there, they are nothing short of magnificent - and if you've seen The Lord of the Rings, you'll certainly agree. Strike slip faults are of course not static - they move continental crust around horizontally - so New Zealand (the emergent, major landmass of Zealandia) has undergone quite a bit of change as it has been sheared over the course of the Cenozoic. Just as the rocks to the west of the Alpine Fault are part of the Australian Plate, the rocks to the east are part of the Pacific Plate. South of the South Island, the plate boundary goes back into the ocean, forming the Puysegur trench between the Australian and Pacific plates, which continues south (with some name changes) towards the Macquarie Triple Junction where a spreading ridge is producing more oceanic crust, resulting in the slow push of the Pacific Plate north and west, causing all of the subduction and also the slow movement of the parts of New Zealand east of the Alpine Fault north, scraping against the rest of the landmass to the west.

*There is a volcanic arc that runs northeast along the Kermadec and Tonga trenches, and this trench makes a left (westward) turn at Tonga/Fiji. Tonga marks the eastern-most volcanic arc in the south/tropical Pacific, defining a major geological boundary called the "Andesite Line". Andesite at minimum requires some continental-ish rock enriched with at least a little bit of silica to form - and andesitic volcanoes are on the bigger end of things, forming towering stratovolcanoes, also known as composite volcanoes, like Mt. St. Helens, Mt. Rainier, Crater Lake (formerly Mt. Mazama), Mt. Fuji, and Mt. Taranaki in NZ (Mt. Taranaki stood in for Mt. Fuji in "The Last Samurai" and Mt. Doom in Lord of the Rings). Stratovolcanoes tend to explode, and some of the most famous eruptions on earth - Krakatoa and Tambora - erupted west of the Andesite Line, in Indonesia. All volcanism east of the Andesite Line consists of intraplate volcanism only - volcanoes shooting up magma at hotspots, burning holes in oceanic crust, forming un-enriched heavy, iron/magnesium rich and super runny basaltic lava. East of the Andesite Line you get Hawaiian-style eruptions - eruptions you can walk, run, or drive away from. West of the Andesite Line? Explosive eruptions that might kill you by pyroclastic flow, steam explosions, tsunamis, or regional devastation that might alter the long term livability and economy of your island.

There are plenty of older rocks in the country, but the story of Zealandia really starts in the Cretaceous when it finally split apart from Australia - and no self-respecting Kiwi would want to dwell on a time period where Zealandia was simply part of Australia! Around 80 million years ago, continental rifting resulted in Zealandia breaking off the east coast of Australia and migrating eastward. A brief refresh: the famous supercontinent Pangea formed during the Carboniferous period some 300 million years ago, and began to rift apart around 200 million years ago around the Triassic-Jurassic boundary. By the late Jurassic, Pangea had rifted into two major landmasses separated by a narrow North Atlantic: Laurasia (North America, aka "Laurentia", and Europe/Asia), and Gondwana (South America, Africa, Madagascar, Antarctica, Australia, India, and Zealandia). By the early Cretaceous, the South Atlantic began to form, separating South America from Africa; Africa started drifting North, with Madagascar also separating from everyone else, and India began skittering northwards at a breakneck pace (and it would eventually collide with Asia around ~40 million years ago in the late Eocene, beginning the uplift of the Himalaya, which are of course still being uplifted today).

Continental geography of the south pole during the Paleocene and Eocene, prior to the final separation of Antarctica from South American and Australia and the resultant formation of the circum antarctic current. From Reguero et al. (2013).

What this resulted in was a big of a strange remnant of Gondwana: South America, Antarctica, Australia, and Zealandia (for a short while) remained connected in the "west" to the Antarctic Peninsula (which is in West Antarctica) and Australia to the north of East Antarctica, and Zealandia stuck on to the east coast of Australia. Zealandia separated first, and drifted at a leisurely pace (much, much, much slower than India), while Australia, and South America remained attached to Antarctica until the Eocene epoch. During the mid-late Eocene, each of these landmasses finally began to rift apart from Antarctica. It's uncertain which happened first, but what's very neat is that thanks to fossils from Seymour Island (same locality as Llanocetus, the oldest baleen whale), there were South American mammals inhabiting the Antarctic Peninsula well into the middle Eocene. Some of these fossils indicate that there were early Xenarthrans present - the group including modern armadillos, sloths, and anteaters - along with litopterns, an extinct group of placentals also unique to South America - and a host of different marsupials with South American links. Plant fossils indicate a temperate forest dominated by southern beech (Nothofagus), very similar to the native forest in New Zealand today. Given these fossils, it's likely that South America was still firmly attached - but the opening of the Drake Passage between Antarctica and South America is still unclear. The date of separation between Australia and Antarctica - the formation of the Tasmanian Seaway - is better understood, and seems to have opened to such a degree to permit deepwater circulation by 33.5 mya. This changed everything - locally, but also on a global scale - with permanent consequences for the earth since.

Geographic and climatic changes associated with the formation of the Circum Antarctic Current (aka circumpolar current) during the Eocene-Oligocene transition. From Nelson et al. (2004).

The final separation of these landmasses finally isolated Antarctica, resulting in the setup of the deep water Circum-Antarctic Current, sometimes called the circumpolar current, or the Antarctic Circumpolar Current (ACC). The ACC is the world's refrigerator: this west to east current prevents a southern hemisphere version of the gulf stream from delivering any warm, moist air - and seawater - to Antarctica. Antarctica, formerly a temperate forest teeming with life similar to its former neighbor continents, became rapidly glaciated at the Eocene-Oligocene boundary. With no possibility of interference of warm air and water, each winter became slightly cooler until it was cold enough to snow year-round, eventually forming the first continental ice sheets on the continent.* The famous La Meseta Formation on Seymour Island, where marine faunal change at the south pole during the Eocene has been best studied - terminated sedimentation, as sea level was lowered considerably below. In many places in the world, the Eocene marine record simply ends and rocks of late Eocene age are overlain by terrestrial rocks, or incised into by erosional surfaces (as nonmarine sedimentation on coastal plains is scattered and unreliable, often haphazardly causing widespread erosion and limited nonmarine deposition). At the famous Egyptian locality Wadi-Al-Hitan ("Valley of the Whales"), for example, the spectacularly fossiliferous marine sequence from which ~10 million years of incredible fossils chronicling whale evolution, ends with the deposition of the shallow marine to lagoonal Qasr el Sagha Formation of latest Eocene age, and is overlain by the nonmarine Oligocene Gebel Qatrani Formation - which produced some pretty famous land mammals like the early proboscideans Moeritherium and Phiomia and the double-horned embrithopod Arsinoitherium. While I would prefer some Oligocene cetaceans of course, maybe it's OK to have gotten some early afrothere 'weirdos' like these, I'd call that a solid tradeoff between marine/nonmarine fossils!

*This is the traditional model of Antarctic glaciation - however, there's some evidence of a smaller ice cap earlier, perhaps during the middle Eocene and even the late Paleocene has been suggested - and the glaciation has also been hypothesized to stem from a decrease in atmospheric CO2 - formerly in the thousands, it dipped below the 600 ppm tipping point, triggering a rapid transition from greenhouse to icehouse conditions. Within the last decade, we recently exceeded 400 ppm CO2, transitioning from a pre-industrial ~280 ppm.

In Europe the Eocene-Oligocene boundary marks an extinction event where many endemic mammals became extinct, and were replaced by invading mammalian species of Asian origin - this faunal difference has been called "Grande Coupure", or "the big break". Cooling during the Oligocene led to limited expansion of grasslands and more temperate forests, and a bit of a reduction in tropical rainforest/jungle habitat that was so common during the Eocene.

Geographic and tectonic evolution of New Zealand, with modern shorelines superimposed. It used to look quite a bit different, and is only elongated into the two islands now because of shearing along the Alpine fault. From Reilly et al. (2015).

In New Zealand, there isn't as much of a stark difference because most of Zealandia remained underwater. middle-late Eocene rocks are plentiful, though sparsely fossiliferous and with sparse outcrops. Terrestrial pollen from NZ shows a transition from warm, humid forests to more temperate forests during this time, but as far as marine rocks are concerned, little much of a difference. In fact, around the Eocene-Oligocene boundary, the sequence is interrupted along the Otago coast by volcanic rocks. The Ototara Limestone - a thick, monotonous tan to white limestone mostly composed of bryozoan fragments* - preserves the Eocene-Oligocene Boundary, marked by the extinction of the foraminifer ("plankton") Hantkenina.

*Also known commercially as Oamaru-stone or Totora-stone, virtually all pre-WW1 buildings in the town of Oamaru are carved from this limestone, making it quite bright/reflective on a rare sunny day, and also a popular source of stone for local sculptors. I still regret not purchasing a Muri Paraoa (whale flukes) I saw for sale at a farmer's market in Dunedin, but it would have come at the cost of a week's groceries and any heat we would have needed.

Highly burrowed unconformities in the middle Oligocene of New Zealand, with the Oligo-Miocene Kokoamu Greensand, Otekaike Limestone and Gee Greensand overlying the Ototara Limestone (early Oligocene). From Thompson et al. (2014).

The first noticeable perturbation in the marine record of NZ is a widespread erosional surface, called by earlier stratigraphers as the "Marshall Paraconformity". An unconformity is an erosional surface, and a paraconformity is one such type - it's basically similar to a disconformity, where there is a difficult-to-identify erosional surface present between rock layers above and below that are parallel in bedding, differing from an angular unconformity where the rocks below have been tilted. The "Marshall Paraconformity" itself has been a locally controversial topic amongst NZ stratigraphers (summarized here by Mike Pole) and in reality might be two or more different unconformities, which seem to have erased 2-3 million years of the marine record in parts of NZ. In the whale-bearing rocks of the south Canterbury Basin, the top of the Ototara Limestone is heavily bored/bio-eroded and even shows evidence of karst dissolution. It has been overlain by the Kokoamu Greensand. Further inland, the Ototara Limestone transitions into the deeper marine Earthquakes Marl, and further inland yet, the Wharekuri Greensand - also overlain by the Kokoamu Greensand. The cause of this erosion is unclear, but may have been driven by some "glacioeustatic" fluctuations in sea level - brief expansions of the Antarctic Ice sheet that temporarily lowered sea level during the middle Oligocene.

Maps of likely emergent land from the Oligocene onward, modified from work by Charles Fleming. From https://slideplayer.com/slide/16841854/.

The last relevant geological event may or may not have happened - but during the Oligocene there was a period of rather high sea level - that may, or may not, have completely submerged Zealandia. This debate was raging just as I got to New Zealand. During the Oligocene, there are basically no terrestrial sediments, and all known Oligocene aged marine rocks are marine. Many geologists argued that this indicated the entire landmass was completely underwater for at least a few million years - highlighting many lineages of terrestrial organisms that seem to have been post-Oligocene arrivals, and the complete absence of native terrestrial mammals, aside from bats, which almost certainly flew across the Tasman sea. However, plenty of scientists - Fordyce included - fervently disagreed, pointing out that there's no shortage of lineages that either 1) are endemic today and have molecular divergence dates from other endemic species pre-dating the Oligocene and 2) some animals like the Tuatara, Sphenodon punctatus - a strange lizard-like reptile that is today unique to New Zealand. This group, the Rynchocephalia, were formerly globally distributed during the Mesozoic (and were quite diverse here in North America during the Triassic), but declined during the early Cretaceous, restricted to what remained of Gondwana (South America, Antarctica, Australia, Zealandia) after becoming extinct in North America, Europe, Asia, and Africa during the early and late Cretaceous. Though no pre-submergance Tuatara are known from NZ, their last occurrence outside Zealandia is from the earliest Paleocene of Patagonia, strongly suggesting that they've been endemic to Zealandia since the Paleocene.

Ewan Fordyce teamed up with Ken Rose, Hans Dieter-Sues, Carolina Loch, and Mike Gottfried for a project called "The Lost Mammals of Zealandia", a search for Paleogene fossil land mammals in shallow marine sediments where he had found some evidence that terrestrial fossils might be found. As of 2014, no precious mammal teeth had been discovered during the pilot project, but a single crocodylian tooth had been recovered - the oldest from the continent. The hope was, if any land mammal teeth were found, they would be readily identifiable and with likely biogeographic signal (e.g., these teeth clearly resemble species from Australia, which, all nationalistic joking aside, is the most predictable affinity for any Paleogene Zealandian mammals). The search continues.

The New Zealand Geological Time Scale and mid-Cenozoic Stages

In a characteristic display of independence, New Zealand proudly boasts its own Geologic Time Scale. I had some knowledge of this prior to my arrival in 2012, but had a bit of a baptism by fire my first few months. New Zealand is so isolated, that many of the correlations of marine rocks in Zealandia require careful comparisons between other NZ localities, rather than Australia or further afield - necessitating to a degree its own time scale. Australia has its own time scale, for similar reasons, though it is less widely used than the international scale.* These are chronostratigraphic units, relating physical rock layers to specific periods of time. Most chronostratigraphic units are based on a reference section somewhere on earth. In the case of the Duntroonian Stage - one that we're going to talk about the most in this series, I think - is based on exposures of the Oligocene Otekaike Limestone in the vicinity of Duntroon, New Zealand. More on Duntroon later.

*Along the west coast of North America, we have several timescales for each type of microfossil - the diatom zones, initially divided into stages with roman numerals, and benthic foraminiferal stages like the Eocene-Oligocene Narizian, Refugian, and Zemorrian stages - sadly, best a cudgel-like biostratigraphic tool rather than a scalpel. In the past two decades Pacific coast stratigraphers have more completely adopted the international stages defined by the ICS, largely defined on European localities.

The New Zealand geologic time scale: from Raine et al. (2012).

For the period of time concerning fossil whales, we're really focused on the Bortonian, Kaiatan, Runangan, Whaingaroan, Duntroonian, and Waitakian stages. The Bortonian through Runangan are Eocene in age, with the Bortonian confusingly being broadly equivalent to the Bartonian middle Eocene stage; the Kaiatan and Runangan are generally late Eocene in age, roughly equivalent with the international Priabonian stage. These three stages comprise the Arnold Series - named after strata exposed along the Arnold River in the West Coast district of the South Island. Likewise, the Runangan is

The next three are roughly coincident with the Oligocene, but actually include the last million years of the Eocene and the first two million years of the Miocene. The Whaingaroan stage is broadly equivalent to the Rupelian of international usage (early Oligocene), while the Duntroonian represents the early Chattian (late Oligocene), and the Waitakian stage represents the latest Oligocene and first million years or so of the Miocene. These three stages make up the Landon Series, named after Landon Creek, between Oamaru and the mouth of the Waitaki River. The Whaingaroan is named after strata in the vicinity of Whaingaroa, south of Auckland on the North Island, whereas the Duntroonian derives its name from the hamlet of Duntroon along the Waitaki River in South Canterbury - which also happens to give its name to the following Waitakian stage.

Generalized stratigraphy of the southern Canterbury Basin (occasionally called the Waitaki Basin by some authors, but not Otago geologists). From Thompson et al. (2014).

A Brief Introduction to mid-Cenozoic Stratigraphy of the Canterbury Basin

Deposition of the Canterbury Basin starts in the Cretaceous, and the late Cretaceous Katiki Formation has produced spectacular fossils like Kaiwhekea - the "shag point" plesiosaur*, and a sparsely fossiliferous sequence from the Paleocene and early Eocene.

*'Shag' is an archaic English name for cormorants. Fordyce always called this specimen "Shagosaurus" to get some laughs.

Some panoramic shots of some of the more important Oligocene paleocetological localities in North Otago and South Canterbury. The holotypes of Waipatia, Aureia, Horopeta, Waharoa, Tokarahia, Tohoraata, Whakakai, Toipahautea, Kairuku, and Plotornis archaeonautes (and more) all came from within these photos or slightly out of frame. Photos by me, 2012-2014.

Waihao Greensand: The Waihao Greensand is middle to late Eocene in age, and best exposed in the vicinity of Waihao in south Canterbury. This unit is a massively bedded glauconitic sandstone, frequently a grayish green color. Invertebrates are rare but include a fossil lobster. Many bony fishes are reported form otoliths. The leatherback sea turtle Psephophorus terrypratchetti was reported, along with specimens of Zygorhiza (see below), are the best known vertebrates from the Waihao Greensand.

Ototara Limestone: One of the more important sedimentary units, historically used as a source of building stone; most of the older buildings in the coastal town of Oamaru are built out of this material, colloquially called "Oamaru Stone" (some of the parts of the Geology and Registry buildings at Otago are made of this material as well). It's also used for stone carvings, quite common on the South Island. The Ototara Limestone is dominated by bryozoan fragments, giving it a medium to coarse sandy texture. It's frequently massively bedded, and in the vicinity of Kakanui, interfingers with lavas from small marine cinder cones. The Ototara Limestone is Eocene through early Oligocene in age. The very first fossil penguins ever reported were discovered in the Ototara Limestone in the 1840s - indeed, Palaeudyptes antarcticus was named in 1847 by none other than Darwin's bulldog, Thomas Huxley. Later, the titanic penguin Pachydyptes was also named from the Ototara. The only cetacean to be reported from this unit is the "Protosqualodont" of Keyes (1973).

Amuri Limestone: This unit is a lateral equivalent of the Ototara Limestone, and exposed in North Canterbury. It is a chalky unit consisting mostly of coccoliths and foraminifera deposited in outer shelf to slope settings. So far only one fossil cetacean is known from this unit, ZMT 62.

Earthquakes Marl: This unit is poorly exposed and has not produced much in the way of significant vertebrates, but is a lateral equivalent of the Ototara Limestone, typically exposed further inland. It is the lowermost unit exposed at "The Earthquakes" and Waipati. It consists of gray calcareous siltstones

Kokoamu Greensand: This unit is a sandy, invertebrate rich outer shelf deposit consisting of pervasively burrowed, massively bedded glauconitic sandstone. It is considerably more friable and tends to weather away rapidly at the base of cliffs, and natural exposures typically include only the uppermost couple of meters below the Otekaike Limestone. The Kokoamu is uppermost Whaingaroan in age to upper Duntroonian (~28-26 Ma). Common fossil invertebrates include brachiopods and scallops, especially at the top of the unit, where it becomes more calcareous - leading to a gradational contact with the overlying Otekaike Limestone. Fossil sharks, penguins, and cetaceans are common; fossil cetaceans include Mammalodon hakataramea, Kekenodon onamata, Tohoraonepu nihokaiwaiu, Tokarahia lophocephalus, Tohoraata waitakiensis, Matapanui waihao, and Toipahautea waitaki. Two species of dolphins have been named from the Kokoamu, both waipatiids - Awamokoa tokarahi as well as Nihohae matakoi, though there is an unnamed squalodontid as well; doubtless there are others. Penguins include the giants Kairuku waitaki and Kairuku grebneffi, and the earlier named Archaeospheniscus lowei, and Platydyptes marplesi. The Wharekuri Greensand and "Kekenodon beds" are lateral equivalents of the Kokoamu Greensand.

Otekaike Limestone: This unit overlies the Kokoamu Greensand and the two units constitute a depositional package. The Oteikaike Limestone is glauconitic at the base and grades up into a sandy, foraminiferal limestone, representing middle shelf deposition and preserves abundant invertebrates - most common are bivalves, bryozoans, brachiopods, gastropods, and tube worms, but crinoids, basket stars, and cold water corals (including octocorals) are also present. The Otekaike Limestone is massively bedded and a ridge former, and many spectacular cliffs are developed in North Otago and South Canterbury; some of these cliffs even appeared in the first Hobbit movie (though possibly could have been the Weka Pass Limestone). It dates to the late Oligocene, being about 26-22 million years old, or Duntroonian through Waitakian. Locally it is an important source of agricultural lime, and Hakataramea Quarry is a critical source of such lime. The Weka Pass Limestone in North Canterbury is a northern equivalent of this unit (the cliffs in the final battle in The Lion, the Witch, and the Wardrobe were filmed at a famous Weka Pass Limestone exposure) - though it is nowhere near as rich in fossil vertebrates. This unit is easily the most heavily studied in New Zealand. Many fossil fish and sharks, including the giant shark Carcharocles angustidens, the giant moonfish Megalampris keyesi, and the billfish Aglyptorhynchus hakataramea are all known from the Otekaike Limestone (though far down in the lower, glauconitic limestone in the case of the former two). Penguins include Platydyptes and the recently named dwarf penguin Pakudyptes. Fossil cetaceans are common and include a kekenodontid archaeocete (new genus and species), waipatiid dolphins (Waipatia maerewhenua, Waipatia hectori, Nihoroa reimaea, Aureia rerehua, Otekaikea marplesi, Otekaikea huata), at least one squalodontid (the Earthquakes squalodontid), eomysticetids (Tokarahia kauaeroa, Tohoraata raekohao, Waharoa ruwhenua), "Tsai's whales" (Whakakai waipata, Toipahautea waitaki, Horopeta umarere), Mauicetus and friends (Mauicetus parki, and ZMT 67). There are other "interesting" (to put it extremely mildly) cetaceans I can't talk about, but at least one has been reported in a conference abstract: a mysticete with an arched rostrum, OU 22224, which Ewan originally considered to be an Oligocene balaenoid (right whale), but at present, might instead be something more archaic (see part 2).

Gee Greensand: The Gee Greensand is a thin, friable glauconitic sandstone of early Miocene (Otaian stage, ~19-21 Ma) age and is mostly exposed close to the coast, such as in the vicinity of Kakanui (and poorly exposed at that). The Gee Greensand has produced a single fossil cetacean, Tangaroasaurus kakanuiensis.

Mt. Harris Formation: The Mt. Harris Formation conformably overlies the Otekaike Limestone and consists of somewhat deeper marine siltstone; in the vicinity of Awamoa Beach, numerous light gray siltstone concretions have been collected that contain cetacean bones. Few fossil cetaceans have been reported from this unit, other than a partial skull of Prosqualodon. Many others are sure to follow. The Mt. Harris Formation is Otaian to Altonian, roughly 21-18 Ma in age.

Caversham Sandstone: The Caversham Sandstone is a lateral equivalent of the Mt. Harris Formation, and is a thick, massively bedded yellow sandstone that forms the spectacular coastal cliffs southwest of Dunedin as well as further north of the Otago Peninsula from Karitane nearly to Shag Point. Only one fossil odontocete has been formally named from this unit, "Prosqualodon" hamiltoni, a large Phoberodon-like beast (see part 3); several smaller dolphins, including kentriodontids, were studied by Gabriel Aguirre-Fernandez as part of his Ph.D. thesis and await formal publication. The Caversham Sandstone is Otaian to Altonian in age (21-17.5 Ma).

The southeast cliff at Hakataramea Quarry, aka Haugh's Quarry - this was the original natural exposure, quarrying is to the left. The holotypes of Toipahautea and Horopeta were collected between where I was standing and where Ewan (red shirt) is, and the large hole he's examining is where the unnamed "Chocolate whale" was excavated. The grass-filled hole in the quarry at the upper left is where the paratype skull of Waharoa was collected. The olive green layer at the base of the cliff is the top of the 'mid' Oligocene Kokoamu Greensand, and the rest is all upper Oligocene Otekaike Limestone. Photo by me, 2013.

Tunnel Beach, South Otago, New Zealand - these impressive cliffs are exposures of the somewhat younger Caversham Sandstone (early Micoene). No mysticetes (or archaeocetes) from this unit, but I'll cover some of the odontocetes from this unit in part three. Photo by me, 2013.

The Fossil Record of Archaeocete Whales in New Zealand: Basilosauridae

Archaeocete whales - the ancestors of baleen whales and toothed whales - are predominantly known from the Eocene epoch, and document how hoofed mammals began experimenting with a semiaquatic existence, rapidly changing from an herbivory to carnivory, and the slow transition from a running mammal to one that swam, first quadrupedally, and then eventually with flukes and flippers. The earliest groups of archaeocetes, the semiaquatic raoellids, pakicetids, ambulocetids, are known only from India and Pakistan. The remingtonocetids were the first to be found preserved in marine strata, and have been found slightly further afield in Egypt (Rayanistes) and possibly eastern North America. The protocetids, the last group to have any ability to support their weight on land - have now been found in Indo-Pakistan, Egypt, Morocco, Europe, Togo, the southeastern USA, and most recently, Peru. The last group, the Basilosauridae, have a near-worldwide distribution - most famously they are known from Egypt and the southeastern USA, but there have been a number of amazing discoveries in Peru, such as well-preserved Cynthiacetus peruvianus and the titanic whale Perucetus colossus, and many additional as-yet undescribed species and specimens from the "valley of the archaeocetes".

The very first archaeocete fossils (1-5) collected form New Zealand in the late 19th century - identified as Dorudon by Fordyce (1985). From Fordyce (1985).

This latter group is the only classical group of Eocene archaeocetes known from New Zealand. The first known specimen was a collection of three associated teeth from the Waihao Greensand of South Canterbury, described by Ewan Fordyce (1985). This specimen has a bit of an interesting post-collection history. One of these teeth, a single premolar similar to Saghacetus osiris, was present in the collections of the NMNZ collections at what is now Te Papa Tongarawea - the NZ national museum in Wellington (I'll just call it Te Papa if it comes up again), and mixed in with the type specimen of the problematic early whale Kekenodon onamata (keep reading), but morphologically and having some preservational differences. Fordyce noticed this in 1975 and concluded it was from a different specimen, but it bore no markings or associated notes to indicate exactly where it was from. Two years later, while visiting the Canterbury Museum in Christchurch (the other big city on the South Island other than Dunedin, and where Ewan did his Ph.D. research), he found a specimen consisting of a canine-like tooth and a fragment of a root, bearing the identification of "Crocodile Waihao". These other two specimens were preservationally similar to the mystery tooth found at Te Papa, but also share similar enamel thickness and surface tecture, along with similar rock attached - which happened to be similar looking greensand. What really clinched the identification was the fact that the three tooth fragments have identical glue attached to them, and were at one point affixed to a sheet of card and evidently put on display, and sunlight damaged the card but left little shadows showing the outlines of the teeth - and there was an outline matching the premolar found at Te Papa. The specimen was united and assigned a new specimen number at Canterbury Museum after this detective work. It is thought to have been collected very, very early - perhaps by the early geologist-explorer Julius von Haast, and Fordyce speculated that the premolar may have been taken to Te Papa in the 1880s during James Hector's study of what he later named Kekenodon onamata - the specimen was not figured or considered part of the type specimen by Hector. Fordyce concluded that these teeth are assignable to some sort of "dorudontine"* basilosaurid, and made comparisons with Saghacetus osiris from the uppermost Eocene of Egypt, and indicated that the tooth is a bit smaller than Zygorhiza from the USA. Critically, Fordyce also summarized other fragmentary records that had been assigned from the Oligocene of Australia and New Zealand and concluded that most of these other specimens represent archaic toothed mysticetes and odontocetes - the New Zealand specimens of which I'll review in this same series. As a result of this revision, Fordyce (1985) pointed out that this was the first definitive record of an archaeocete as well as the oldest known cetacean from NZ.

*The taxonomy of the Basilosauridae has been revised several times - most notably by Kellogg (1936), but later by Barnes and Mitchell (1978), who left lasting definitions of the "Dorudontinae" and "Basilosaurinae" - two subfamily names, placed here tactically in scare quotes - which have in recent years become less-than-useful ideas. Essentially, the Basilosaurinae was used to contain Basilosaurus cetoides and Prozeuglodon isis, gigantic species with elongated thoracic and lumbar vertebrae. However, P. isis was later reassigned to Basilosaurus and recombined as Basilosaurus isis, essentially making gigantic size and elongated vertebrae unique to the genus Basilosaurus - and making the subfamily not needed, because the "Dorudontinae" ended up including all other basilosaurids. With Perucetus, Cynthiacetus, Tutcetus, and the Basilotritus-Platyosphys-Pachycetus-Aithacetus quagmire, the situation has changed somewhat, and pending phylogenetic analysis of the family, perhaps some subfamilies may still be useful, but not until then.

The first truly significant archaeocete fossil from New Zealand, a well-preserved braincase with periotic and associated teeth from the Bortonian Waihao Greensand of south Canterbury, identified as Zygorhiza. From Kohler and Fordyce (1997).

Closeup of the periotic and tooth of the Waihao Greensand Zygorhiza, from Kohler and Fordyce (1997).

Further Eocene archaeocete material would not be discovered until 1991, when collector P.A. Maxwell found a partial basilosaurid skull, and further field trips from 1992-1995 recovered a few additional specimens including teeth and some vertebrae. Owing to the rarity of specimens in the Waihao Greensand, and their close association, these specimens - though assigned different numbers - were considered to be one specimen. These specimens formed part of the basis for Richard Kohler's PhD thesis at Otago, and were formally published by Kohler and Fordyce (1997). These specimens were assigned to Zygorhiza, previously known only from the uppermost Eocene Yazoo Clay and equivalent units on the gulf coast of the USA - chiefly Louisiana, Mississippi, and Alabama. Zygorhiza has been differentiated from other basilosaurids only based on one major dental feature: having a well-developed ridge or cingulum at the base of the cheek teeth, absent in other basilosaurids. An additional dental feature seems to define Zygorhiza: a thick posterior root on the premolars, a vestige of the two posterior roots in earlier archaeocetes and land mammals that fused together. One other key feature is possessing a slightly "telescoped" skull - with the occipital shield, the bone that makes up the back of the braincase - shifted further like as is seen in early mysticetes and odontocetes, and a nuchal crest that forms a slight shelf. In other basilosaurids, it is instead vertical. Uhen (2013) found the top of the skull to be quite variable in Zygorhiza. Regardless, the Waihao basilosaurid possesses all three of these features, and was identified as Zygorhiza sp. by Kohler and Fordyce (1997).

More recently, a neonatal or perinatal archaeocete skeleton was discovered in the upper Eocene Ashley Mudstone of Canterbury and reported by Fordyce and Hiller (2014) in an SVP conference abstract. I saw the specimen in person during my Ph.D. - it is tiny - but has adult-sized periotics, and a skull measuring only about 30 cm, with a number of milk teeth. The specimen has not yet been published.

The holotype fragments of Kekenodon onamata from the "Kekenodon beds" (=Kokoamu Greensand), from Hector (1881).

The Fossil Record of Archaeocete Whales in New Zealand: Kekenodontidae

In November 1880, a fragmentary archaeocete-like whale was discovered by Alexander McKay in the vicinity of Wharekuri Creek in the Waitaki Valley, from an Oligocene aged unit later called the Kekenodon beds, and later correlated with the Kokoamu Greensand. The specimen consists of a set of rather large teeth including incisors, a canine, premolars, and molars, along with the right frontal bone, a periotic, and a bulla. It seems likely to me, and when I suggested this, Ewan seemed to agree - that the original specimen as found in the field likely had rather crumbly, fragmentary bone that did not survive primitive collecting methods. As a result, only relatively durable parts remain. This specimen was named Kekenodon onamata by James Hector in 1881, who thought it may be similar to archaeocetes like Basilosaurus, but also compared it with modern seals; Hector ultimately named it Kekenodon, meaning seal tooth in combined Maori and Greek. Kellogg considered Kekenodon to likely represent a basilosaurid in his 1936 monograph, and Mitchell (1989) generally agreed, but noted the teeth were quite distinct and would necessarily represent a highly derived "dorudontine" - the cheek teeth trend towards having single roots with a trilobate cross-section rather than widely divided double roots, lack a cingulum on the lingual side of the enamel crown, generally more complex surface texture on the cheek tooth roots, and lower molars that have mesial cusps and critically lack this vertical groove called the 'reentrant groove'.

The holotype right frontal bone of Kekenodon onamata - the only non-earbone part of the skull that was preserved. From Corrie and Fordyce (2022).

The holotype periotic of Kekenodon onamata. From Corrie and Fordyce (2022).

The holotype tympanic bulla of Kekenodon onamata. From Corrie and Fordyce (2022).

As early as 2004, Ewan Fordyce considered kekenodontids to be archaeocetes that were very close to Neoceti, and called them "transitional Neoceti". This is quite significant, as prevailing wisdom held that the basilosaurids, specifically the dorudontines if you believed Barnes and Mitchell - were the immediate ancestors of Neoceti. This was informed partially by the holotype of Kekenodon, but also greatly influenced by a suite of new fossils from the Kokoamu Greensand and basal Otekaike Limestone found by Fordyce and his earlier students and museum staff, chiefly in the 1990s (I'll discuss these below). In 2022, Josh Corrie and Ewan Fordyce published the first chapter of Josh's PhD thesis, reevaluating the type specimen of Kekenodon onamata. Though belonging to Te Papa Tongarewa National Museum of New Zealand, the specimen had been on loan to Fordyce for years - all of the really significant whale remains under one roof. I examined the teeth and earbones of the specimen several times during my Ph.D.

The holotype teeth of Kekenodon onamata - top image shows the anterior incisors/canines, and the bottom image shows the premolars and molars. From Corrie and Fordyce (2022).

The above-mentioned differences in tooth shape are rather trivial when compared to most toothed mysticetes, however: the teeth are rather enormous and generally basilosaurid-like in most respects, with a similar pattern of heterodonty - amongst toothed mysticetes, premolars and molars look nearly alike, but within basilosaurids, each tooth position can be picked apart and this is true of Kekenodon: each premolar position is obvious, as are the molars. Slight differences by position in toothed mysticetes are further smeared by having an increase in tooth count (polydonty). As for tooth size, the only toothed mysticetes with similarly enormous teeth are Coronodon (not known until the 1990s), Llanocetus, and Mystacodon (not known until the late 2000s).

The spectacular skull of OU 22294 - an unnamed genus and species of kekenodontid currently under study by my former labmate Josh Corrie. He's in the final stages of getting this beast named. This is the only published image of the specimen, so I'll stick to features that are clear from the image: it obviously has an un-telescoped skull and is most similar to small basilosaurids like Zygorhiza, but the occipital shield is positioned much further anteriorly, the bony naris further posteriorly, it lacks a sagittal crest, and has an open mesorostral groove - all features linking it more closely with the Neoceti. From Clementz et al. (2014).

The most spectacular specimen, however, is OU 22294 - a nearly complete skull that in outline and general morphology looks quite a bit like a small basilosaurid, but does have a bunch of features shared with toothed mysticetes like Coronodon and especially Mystacodon. The specimen is still under study by my Otago labmate and colleague Josh Corrie, so I will refrain from remarking on anything about this specimen that isn't already in the literature somehow, or what is clear from published images (e.g. Clementz et al., 2014, above). Ewan told us during our program that when they first came upon the specimen in the field, sticking out of an overhang in a cliff, he suspected it was a squalodontid. However, during the initial excavation, a fracture developed in the rostrum, revealing that the mesorostral groove was roofed over - indicating that it was some sort of archaeocete. In early mysticetes and all odontocetes, there is a continuous groove present along the rostrum - the left and right premaxillae never really contact. In the early dolphin Xenorophus, the groove is narrow but the bones do not contact; a similar situation is present in Mystacodon. In Coronodon havensteini, the premaxillae contact at the tip but only for a few centimeters; aetiocetids are similar. In virtually all Oligocene dolphins diverging after xenorophids, the mesorostral groove is quite wide and continuously separated - then this groove is variably narrowed in modern odontocetes, and occasionally secondarily closed. The bony nares are also positioned further posteriorly - along the middle third of the snout rather than the anterior third - unlike basilosaurids. The braincase of this specimen is quite interesting as it has a Neocete-like degree of telescoping, with the vertex thrust forward; the skull is also quite low in height, much like a mysticete, with a broad occipital shield. The periotic is critically amastoid - in other words, the posterior process - also called the mastoid process - is shortened and not exposed on the lateral skull wall. There are some other fascinating features I'd love to discuss, but will wait until Josh's paper is published (and, will necessarily devote an article or two on this blog to the strange kekenodontids).

The holotype skull fragments of Tohoraonepu nihokaiwaiu, including the right frontal, right squamosal with articulated periotic, and the right tympanic bulla. From Corrie and Fordyce (2024).

The holotype teeth of Tohoraonepu nihokaiwaiu. From Corrie and Fordyce (2024).

Somewhat more recently, Josh published a paper in the Journal of the Royal Society of New Zealand naming a new fragmentary kekenodontid, Tohoraonepu nihokaiwaiu, from the Kokoamu Greensand (Corrie and Fordyce, 2024). Tohoraonepu translates to "sand whale", referring to the occurrence of this whale in greensand; nihokaiwaiu translates to "baby teeth". This specimen consists of an associated dentition and partial braincase with bulla and periotic, cervical, thoracic, and lumbar vertebrae, scapulae, partial humerus, radius, and ulna. The specimen is a juvenile, but also clearly much smaller than Kekenodon onamata as the teeth are quite smaller - suggesting a skull and body length (at least at death) that was about half (skull size) to one third the size (estimated body length). The teeth are the most interesting parts of the specimen - they are all developmentally young, and though they have hollow pulp cavities not yet filled, and an apparently diphyodont dentition in general: there are a mix of deciduous (milk) teeth with permanent molars, recording the only known occurrence of diphyodonty in a post-Eocene cetacean. The teeth are much more basilosaurid-like than in Kekenodon onamata, with widely separated root lobes, but have similar molars with mesial cusps that also lack the 'reentrant groove' to accommodate the upper molars. The enamel is extremely smooth - there are no apparent ridges or bumps, aside from a few subtle striations along the caniniform teeth and a few along the lingual (tongue side) of the cheek teeth), and also completely lack cingulum. There's no remnant of a third root, like Kekenodon. The teeth actually quite closely resemble Coronodon in many regards, but differ in having lower crowns and shorter roots (and their smaller size). The bulla looks very similar to aetiocetids, squalodontids, and eomysticetids, and more closely resembles these than basilosaurid bullae (or even the admittedly archaeocete-like bulla of Llanocetus, for that matter). The periotic is amastoid, and generally more similar to Coronodon than to any basilosaurid, especially in lacking a tall superior process.

Two southerners: Ewan Fordyce (left) speaking with his old friend and colleague Al Sanders (right), while examining what would become the holotype specimen of Coronodon havensteini five years later. Photo taken by me, 2012.

One last word on kekenodontids - I had seen some line drawings of the "Charleston toothed mysticetes" (now the family Coronodonidae), but unlike most other visitors to the Charleston Museum who examined these and never inspected a kekenodontid, I saw these specimens in 2012 after having seen Kekenodon onamata and other kekenodontids from New Zealand earlier in the year when I started my Ph.D. When I saw the periotic of the juvenile specimen of Coronodon havensteini, ChM PV 4745, and the specimen that would five years later become the holotype of the same species (CCNHM 108) - I immediately noticed how similar in morphology they were. From that point on I began wondering if the "Charleston toothed mysticetes" were North Atlantic kekenodontids.

The Fossil Record of Toothed Mysticetes in New Zealand

A handful of notable specimens that are clearly identifiable as toothed mysticetes have been collected from New Zealand. They are not quite as spectacular as some of the toothless mysticetes or the kekenodontids, but hold some promise of further, future discoveries and hint at some pretty neat looking critters. I'll note that, prior to Josh Corrie's thesis, Ewan considered certain specimens now recognized as kekenodontids to be possible toothed mysticetes - like the holotype of Tohoranepu. However, that changed once Josh started working on these specimens and finding more similarities with Kekenodon, and sure enough - they form a tightly supported clade in all of his phylogenetic analyses.

The teeth of OU GS 10897, the "protosqualodont" of Keyes (1973). This enigmatic specimen, likely to be a llanocetid, also includes a partial skull that is still under study by Felix Marx and the late Ewan Fordyce. This image is from Keyes (1973).

The earliest published specimen is the "protosqualodont" of Keyes (1973), otherwise known only as OU GS10897. This specimen consists of a couple of teeth reported by Keyes - and these teeth are seriously unique amongst cetaceans. They are robust, rather large teeth and relatively low-crowned, with radially oriented, stout accessory cusps with rugose enamel resembling Llanocetus denticrenatus. The premolar possesses one very archaeocete-like feature - there is a large 'protocone shelf' and a bulge on the posterolingual part of the tooth - and the posterior tooth root is thick, with a vertical groove - greatly resembling protocetid whale teeth, perhaps to a degree more than many basilosaurids. Though Keyes reported only on two teeth from the specimen, there was a partial skull embedded in a slab of limestone that was cut from Gay's Limestone Quarry - a quarry in the lower Oligocene Ototara Limestone, aka the famous 'Oamaru stone'. The specimen has an interesting post-collection history, and if memory serves, the quarry manager had the limestone slab tipped up against the wall years after Keyes reported on the teeth, and Ewan convinced the manager to donate the specimen. I won't comment on the skull anatomy, other than to mention it is similar to Llanocetus - and typically plots out in Felix Marx's various phylogenetic analyses as the sister taxon to Llanocetus. Predictably for the time, like many of these problematic strange teeth from the Oligocene, Keyes identified the specimen as some sort of squalodontid.

The holotype tooth of "Squalodon" serratus from the Weka Pass Stone of Canterbury, New Zealand - this specimen is likely to be something like Janjucetus from Australia. from Glaessner (1972).

The second is "Squalodon" serratus, which is an isolated tooth reported from North Canterbury by Davis (1888). This tooth has cusps like a basilosaurid, but is rather small, and narrow, rather than being a large, serrated triangle. The specimen was collected from the Weka Pass Stone of Canterbury, which is a lateral equivalent of the Otekaike Limestone. Glaessner (1972) reassigned the specimen to Squalodon - something later works by Fordyce disputed. Fordyce and Marx (2016) considered the specimen to possibly represent a southern hemisphere aetiocetid, though Ewan privately told me in 2013 or 2014 that it was likely to be from a mammalodontid, being particularly similar to Janjucetus - and I'm quite inclined to agree.

The jaw fragment of ZMT 62 - a possible small bodied llanocetid from the Whaingaroan (early Oligocene) Amuri Limestone. This specimen is not very big, slightly smaller than Zygorhiza. From Fordyce (1989).

The third is an unnamed specimen, ZMT 62 - an isolated mandible fragment with some partial teeth from the Amuri Limestone of North Canterbury. This fragment has a relatively shallow mandible with a nearly circular cross-section, clearly differentiating it from basilosaurids with deeper, oval cross-sections - however, the teeth are quite large, relatively and absolutely. Fordyce (1989) described this specimen and made comparisons with archaeocetes as well as Oligocene odontocetes and toothed mysticetes, concluding that the specimen most likely represented a toothed mysticete of some sort. In our 2017 paper on Coronodon, we actually coded the specimen into our analysis, and into our 2023 matrix for the Coronodon monograph, and in each case this specimen has formed a sister-taxon relationship with Llanocetus denticrenatus. The teeth are large and do have elongate cusps, similar apicobasal striations, and in all likelihood, a high number of accessory cusps. The specimen is likely to be a llanocetid, but further specimens are needed. Though of similar age and affinities, the specimen is almost certainly a different llanocetid than the "protosqualodont" of Keyes, outlined above - suggesting that the early Oligocene of New Zealand likely had two different llanocetids.

The holotype braincase, tooth fragments, and tympanic bulla of Mammalodon hakataramea, with the skull (H on left side) and tympanic bulla (G-K on right side) of Mammalodon colliveri from Australia for comparison.

The fourth and last example is actually named, like "Squalodon" serratus, but is also reasonably complete so as to be diagnosable - like the unnamed "protosqualodont". This specimen consists of the 'vertex' part of a braincase associated with a complete tympanic bulla and some partial teeth - collected by Ewan Fordyce and his field assistant/student Craig Jones and preparator Andrew Grebneff in 1987 from a stream exposure of the Kokoamu Greensand in Sisters Creek, nearby the unusually productive "Haugh's Quarry" in Hakataramea Valley in south Canterbury (many more finds from Haugh's Quarry to be covered in the next two posts). Felix Marx and Ewan Fordyce published this specimen in 2016 and named it Mammalodon hakataramea. Though fairly incomplete, the specimen is quite clearly referable to Mammalodon, with a similarly shaped cranial vertex but that is somewhat narrower and subtriangular. Along with some subtle differences in the shape of the tympanic bulla, M. hakataramea also has teeth that are worn down to the gumline - the teeth being reduced to roots. Along with specimens like "Squalodon" serratus, Mammalodon hakataramea indicates that mammalodontids inhabited the continental shelves of Zealandia along with Australia. Thus far, mammalodontids have not been reported outside these regions (aside from a partial dentition from the lowermost Miocene of Malta), and I hope at some point we might hear of similar finds made from the Oligocene of South America or even the North Pacific.

A partial tooth of Llanocetus sp. from the Chatham Islands. From Marx and Campbell (2025).

Most recently, Felix Marx and Hamish Campbell have published a short article on a fragmentary tooth from the Chatham Islands that superficially resembles a basilosaurid tooth - collected by Bob Weston, but from an unknown locality. The Chatham Islands are about 800 km east of the South Island and expose rocks of Cretaceous, Paleogene, and Neogene age. Based on the preservation of the specimen, it is considered most likely to originate from Manganui Beach. Most of the rocks here belong to the Tioriori Group, which is mostly Paleocene in age (and has produced an important assemblage of earliest Paleocene sharks from the Takatika Grit). Instead, there are deposits of the upper Eocene Te Whanga Formation. The specimen is admittedly not spectacular, but preserveds enamel ridges like Llanocetus, and a low, 'palmate' crown - rather than a high triangular one seen in basilosaurids. The tooth is quite a bit larger than the holotype of Llanocetus denticrenatus, but matches the size of gigantic teeth of Llanocetus sp. reported more recently from the same rocks in Antarctica.

Next up: baleen-bearing whales from the 'mid' Cenozoic of New Zealand.

References Cited