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).
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).
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.
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.
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.
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.
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.
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).
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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 19th 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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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