What a year! Jesus. This year has really sucked for a lot of folks, and given how stressed I've been and how much effort it has taken to do even a minimal amount of research - and still be very, very backlogged on reading new papers (I am about five months behind for the first time in my life) - I imagine that this year's summary of new research may be more useful to most folks than prior years. One thing I can thank 2020 for is the time stuck at home, giving me an opportunity to reflect - and realize I probably should get back to blogging. So, 2020 has been better for blogging than prior years (and this post is going up on time instead of like... May). As per usual - please let me know if I have forgotten something. However, please double check the 2019 post to make sure that it wasn't actually published 'online early' in 2019 with a formal publication date of 2020, in which case I probably already covered it last year. Also, don't you dare suggest I try to standardize formatting... on a blog post. Don't be daft.
Bell et al. 2020 - First fossil manatees in Texas, USA: Trichechus manatus bakerorum from Pleistocene beach deposists along the Gulf of Mexico. Palaeontologia Electronica.
Link: https://palaeo-electronica.org/content/2020/3178-pleistocene-manatees-in-texas
Extant manatees were documented on the Texas coastline as early as 1853, but their reported occurrence in Texas waters has been sporadic and poorly documented until relatively recently. We report eight specimens that document the first occurrence of fossil manatees in Texas, and the westernmost fossil occurrence of manatees in the United States. Seven of the specimens were collected along McFaddin and Caplen beaches on the northwest coast of the Gulf of Mexico; one was recovered from Corpus Christi Bay. The fossil specimens reported here include a mandibular symphysis fragment diagnosable as the extinct morphotype denoted by the trinomial Trichechus manatus bakerorum Domning, 2005. Other specimens are diagnosed as Trichechus manatus or as Sirenia. They were found on beaches that are known to produce mammalian taxa characteristic of Pleistocene faunas, and our age assessment is based on that association, and the comparable preservation, color, and density of the manatee bones and bones of extinct taxa of Pleistocene age from the beaches. It is not clear whether the fossils represent remains of a resident population, or the fortuitous preservation of vagrant individuals. However, assuming that the ecological tolerances of manatees in the Pleistocene were comparable to the tolerances of extant populations, the presence of manatees in the northwest Gulf of Mexico in the Pleistocene adds an interesting, if enigmatic, data point for paleoenvironmental reconstructions of the region.
Benites-Palomino et al. 2020. Miocene freshwater odontocetes from La Venta, Huila, Colombia suggest independent invasions of riverine environments in tropical South America. Journal of Vertebrate Paleontology.
Link: https://www.tandfonline.com/doi/full/10.1080/02724634.2020.1812078
The two extant genera of strictly freshwater dolphins Inia and Platanista are the result of convergent evolution to freshwater environments with reduced visibility. Characterized by their long snout and small melon, these extant taxa are clustered into two clades, Iniidae in South America and Platanistidae in Southern Asia. Their evolutionary history leading to freshwater environments remains mostly unknown, because many of their related fossil species have been found in marine environments. Here, we report riverine dolphin remains (two rostral fragments and a periotic) from two stratigraphic levels of the late middle Miocene (ca. 12.5 Ma) from La Venta, Colombia. The periotic has a reduced cochlear aqueduct mediodorsally oriented, the anterior process is relatively thin, and the dorsal opening of the facial canal is located lateral to the spiral cribriform tract. The rostral fragments are dorsoventrally flattened; the mandible features two longitudinal ventral grooves, and the premaxilla-maxilla suture of the rostrum is located in a deep lateral groove. These characteristics indicate that the specimens belong to Platanistidae, the lineage of the Ganges river dolphin Platanista. Platanistids had also been recorded on coeval strata from the Fitzcarrald arch, Peru. The occurrence of middle Miocene platanistids in both the La Venta and Fiztcarrald localities suggests that members of this lineage moved into freshwater environments in South America earlier than the ancestors of the modern Amazon river dolphin Inia. The subsequent collapse of the Pebas ecosystem could have played a role in the extinction of non-marine Platanistoidea in South America.
Benites-Palomino et al. 2020. Scaphokogia totajpe, sp. nov., a new bulky-faced pygmy sperm whale (Kogiidae) from the late Miocene of Peru. Journal of Vertebrate Paleontology.
Link: https://www.tandfonline.com/doi/full/10.1080/02724634.2019.1728538
The modern pygmy and dwarf sperm whales (Physeteroidea, Kogiidae) are remnants of a highly diverse group, which flourished in the Miocene oceans. Unlike their modern suction-feeding, deep-diving relatives, the past diversity of this family includes animals with disparate ecological habits. Here, we describe Scaphokogia totajpe, sp. nov., a new species of kogiid based on a well-preserved skull from the upper Miocene strata of the Pisco Formation, Peru. A phylogenetic analysis places S. totajpe as sister taxon of S. cochlearis and divides Kogiidae into two clades: the first including both species of Scaphokogia and the second including Kogia, Koristocetus, Praekogia, and Nanokogia. Similar to S. cochlearis, S. totajpe has a tubular rostrum with a hypertrophied mesorostral canal, a large supracranial basin, and a leftward deviated facial sagittal crest, but it differs by possessing a proportionately shorter rostrum, a reduced projection of the lacrimojugal between the frontal and the maxilla, and a flat occipital shield. The cranial morphology of Scaphokogia indicates that the extent of the nasal complex was greater than in modern kogiids. Furthermore, the overall rostrum shape and the reconstructed muscle insertion sites indicate that Scaphokogia retained some plesiomorphic features related to a more generalist ecology. Inclusion of S. totajpe into the context of the Pisco Formation indicates that during the late Miocene, the Peruvian coastal system was a hot spot for the diversification of physeteroids, with at least four species coexisting. Finally, Scaphokogia totajpe highlights a late Miocene diversity peak for sperm whales in the global oceans, before the Pliocene odontocete turnover.
Benites-Palomino and Urbina, 2020. Physeteroidea (Cetacea: Mammalia) hyper-diversification from the late Miocene of South Pacific, new fossils from the Sacaco area, Arequipa, Peru. Revista Peruana de Biologia.
Link: https://revistasinvestigacion.unmsm.edu.pe/index.php/rpb/article/view/16507
Sperm whales (Physeteroidea) are a group of cetaceans with a restricted modern ecology. The three extant species are a remnant of a group that reached its diversity peak during the Miocene, including five already-described species from the Pisco Formation, Ica-Arequipa, Peru. We report two isolated teeth from the upper Miocene localities of Sacaco and Sud-Sacaco, which correspond with the typical morphology of Physeteridae. This morphology is similar to the one present in northern hemisphere taxa as Orycterocetus or Aulophyseter. Because of this the remains could be related to physeterids with piscivorous habits, so there would not be a niche overlap with other coeval sperm whales. This new registry expands the fossil cetacean community of Sacaco, which was favored by the great diversity of shallow environments that dominated the Peruvian coast until the final establishment of the Humboldt System.
Berta, 2020. Art revealing science: marine mammal palaeoart. Historical Biology.
Link: https://www.tandfonline.com/doi/full/10.1080/08912963.2020.1834541
Apart from mythological drawings (e.g. unicorns and mermaids), some appearing during classical times, marine mammals have been the subject of palaeoart since the seventeenth century. Whales were the first marine mammals to be portrayed in detailed pencil and ink scientific illustrations printed as woodcuts and copper engravings. The early and mid twentieth century witnessed an increase in number of paleoartists, such as Zdenêk Burian and Charles Knight painting in rich, vibrant colours. Later, more attention was focused on portraying the ecologies and environments inhabited by fossil marine mammals based on analogies with living species resulting in restorations of entire animal and plant communities. In the late twentieth and twenty-first centuries, traditional illustrations were complemented by digital art with an emphasis on accurate, realistic portrayals of fossil marine mammals based on new interpretations of their anatomy, ecology, behaviour and habitat. Apart from the inextricable connection of palaeontology and art, palaeoart also serves a vital role in visually communicating science and evolution to the public as portrayed in museum exhibitions and other venues.
Berta and Lanzetti, 2020. Feeding in marine mammals: an integration of evolution and ecology through time. Palaeontologia Electronica.
Link: https://palaeo-electronica.org/content/2020/3136-feeding-in-marine-mammals
Marine mammals are key components of aquatic ecosystems. Feeding strategies identified in extant cetaceans, pinnipeds, sirenians, marine otters, and polar bears are associated with anatomical specializations of the head (rostrum, palate, temporomandibular joint, teeth/baleen, mandible). Genetic and ontogenetic evidence of skull and tooth morphology provide the mechanisms that underlie patterns of feeding diversity. Based on a comprehensive diversity data set derived from the Paleobiology Database, we considered feeding strategies (suction, biting, filter feeding, grazing), prey type (squid, fish, benthic invertebrates, zooplankton, tetrapods, sea grasses), tooth pattern and cusp shape (homodont, heterodont, pointed, rounded, edentulous), and habitat (marine, riverine, estuarine) in fossil and extant marine mammals. These variables were then tested for correlation and their changes through time examined in relation to productivity and climate variables.
We provide an integrated analysis of the evolution of feeding and trophic structure in marine mammals and explore the origin and timing of particular feeding strategies over the last 50 million years. In agreement with earlier reports, updated generic counts reveal that the greatest diversity of pinnipedimorphs and cetaceans occurred during the late Miocene (Tortonian), following the Mid-Miocene Climatic Optimum. These historical data are used as a framework to inform past and present structure and trophic interactions and enable predictions about future marine ecosystems.The drivers of diet and feeding patterns are both environmental (sea level fluctuations, climate change) and biotic (anatomical specializations, competition, predator-prey). The influence of these processes on paleodiversity varies depending on taxonomic group, timing, and geographic scale.
Bianucci et al. 2020. Extensive diversity and disparity of the early Miocene platanistoids (Cetacea, Odontoceti) in the southeastern Pacific (Chilcatay Formation, Peru). Life.
Link: https://www.mdpi.com/2075-1729/10/3/27
Several aspects of the fascinating evolutionary history of toothed and baleen whales (Cetacea) are still to be clarified due to the fragmentation and discontinuity (in space and time) of the fossil record. Here we open a window on the past, describing a part of the extraordinary cetacean fossil assemblage deposited in a restricted interval of time (19–18 Ma) in the Chilcatay Formation (Peru). All the fossils here examined belong to the Platanistoidea clade as here redefined, a toothed whale group nowadays represented only by the Asian river dolphin Platanista gangetica. Two new genera and species, the hyper-longirostrine Ensidelphis riveroi and the squalodelphinid Furcacetus flexirostrum, are described together with new material referred to the squalodelphinid Notocetus vanbenedeni and fragmentary remains showing affinities with the platanistid Araeodelphis. Our cladistic analysis defines the new clade Platanidelphidi, sister-group to Allodelphinidae and including E. riveroi and the clade Squalodelphinidae + Platanistidae. The fossils here examined further confirm the high diversity and disparity of platanistoids during the early Miocene. Finally, morphofunctional considerations on the entire platanistoid assemblage of the Chilcatay Formation suggest a high trophic partitioning of this peculiar cetacean paleocommunity.
Biewer et al. 2020. Insights on the dental evolution of walruses based on new fossil specimens from California. Journal of Vertebrate Paleontology.
Link: https://www.tandfonline.com/doi/full/10.1080/02724634.2020.1833896
Twelve new specimens of fossil walruses are described from four Miocene units in California. The new material represents five taxa: (1) a specimen from the Santa Margarita Formation referred to Imagotaria downsi; (2) a specimen from the Valmonte Diatomite Member of the Monterey Formation referred to cf. Pontolis magnus; (3) six specimens from the Monterey Formation referred to a new species of Pontolis (Pontolis barroni, sp. nov.); (4) one specimen from the Oso Member of the Capistrano Formation referred to a new species of Pontolis (Pontolis kohnoi, sp. nov.); (5) three specimens from the Oso Member referred to a new genus and species (Osodobenus eodon, gen. et sp. nov.). A phylogenetic analysis suggests that both the Dusignathinae and an expanded concept of the genus Pontolis represent monophyletic groups. We provide phylogenetic definitions for clade names of odobenids. Two of the new species are represented by specimens of males, females, and juveniles. Analysis of these specimens shows that the dental anatomy of later diverging basal odobenids is more variable than previously considered. The specific pattern of variation is lineage specific and likely corresponds to the intermediate dental morphology of late Miocene odobenids. Osodobenus eodon, gen. et sp. nov., is the first basal odobenid with tusk-like canines, a longitudinally arched palate, and an enlarged infraorbital foramen. These features are plausibly correlated with benthic suction feeding in the odobenins (Pliocene to Recent) and so Os. eodon may represent a case of convergent evolution of benthic feeding in the late Miocene.
Comments: I still need to read this in detail (long backlog and all) but this is a pretty exciting paper and fills a lot of holes in the walrus fossil record. I saw some of this material back in 2013 (like the Osodobenus skull above). This paper is extremely dense, so it will take some time to digest. These were all specimens in Larry Barnes' 'vault', so to speak, that few researchers ever got a chance to look at. Prior to Barnes' retirement, visiting marine mammal paleontologists were not allowed to peruse collections: you were asked to provide a list of specimens numbers (which you would only know about from published papers) and museum staff would go off and retrieve them for you while you waited at the long wooden table near the prep lab. This system ensured that pesky students and competitors wouldn't happen across one of however many new genera were hiding in LACM collections. Fortunately, it's a new day there, the vault has been cracked open, and new papers like this are finally being published on an incredible 'backlogged' collection.
Bisconti et al., 2020. Marzanoptera tersillae, a new balaenopterid genus and species from the Pliocene of Piedmont, north-west Italy. Zoological Journal of the Linnean Society.
Marzanoptera tersillae gen. & sp. nov., a new balaenopterid from the Pliocene of the Piedmont in north-west Italy, is described based on a partial skeleton and compared with other living and fossil baleen whales. Marzanoptera tersillae shares characters, such as the shape of the supraoccipital, glenoid fossa of the squamosal and zygomatic process of the squamosal, with ‘Balaenoptera’ bertae. We used a computed tomography scan to view parts of the skull that were otherwise impossible to observe, such as the periotic. A phylogenetic analysis based on 355 character states scored from 87 taxa revealed a well-resolved hypothesis of relationships for Balaenopteridae and a general phylogenetic hypothesis for chaeomysticetes. The monophyly of all superfamily- and family-rank clades and of crown balaenopterid species was confirmed. In addition, a monophyletic group including most basal thalassotherian taxa was recovered. The mollusc fauna associated with the specimen was autochtonous and constituted a residual fossil assemblage indicative of an environmental context located below the base of the storm wave, characterized by a low-energy hydrodynamic regimen. Many shark teeth have been found in close association or embedded within the bones, suggesting a possible scavenging action by two shark species on the whale carcass.
Comments: This is an interesting paper, but there's no way that Balaenoptera bertae is a species of Marzanoptera: the two taxa admittedly share some features of the occipital shield, but B. bertae has short zygomatic processes that are aligned anteroposteriorly (a feature fairly unique to Balaenoptera spp.) and also bears a squamosal crease (a feature certainly unique to, and a probable synapomorphy of Balaenoptera). I'm certain that the species I described was properly placed into the extant genus Balaenoptera, and most cladistic analyses by myself and Felix Marx support that.
Bisconti et al. 2020. The earliest baleen whale from the Mediterranean: large-scale implications of an early Miocene thalassotherian mysticete from Piedmont, Italy. Papers in Palaeontology.
Link: https://onlinelibrary.wiley.com/doi/abs/10.1002/spp2.1336
The discovery of an early Miocene chaeomysticete from the Pietra da Cantoni Group in Piedmont (north‐western Italy) allowed for the establishment of Atlanticetus lavei gen. et sp. nov. The new species is represented by a partial skeleton including the periotic and tympanic bullae and has an anatomical resemblance to Atlanticetus patulus (comb. nov.) from the western North Atlantic. The early Miocene age of the new specimen supports the view that it represents the oldest record of Chaeomysticeti from the Mediterranean. A new phylogenetic analysis showed that both A. patulus and A. lavei belong to a radiation of basal thalassotherian taxa. The basal thalassotherians are monophyletic to the exclusion of Cetotheriidae and Balaenopteroidea. The reconstruction of ancestral characters at selected nodes indicates that the group including Atlanticetus and living balaenopterid taxa independently evolved rostra wide at the base, an anterolateral expansion in the tympanic bulla, and a peculiar arrangement of the endocranial foramina of the periotic, exhibiting a noteworthy phenomenon of convergent evolution in feeding and hearing functions with Balaenopteridae. Palaeobiogeographical analysis shows that the North Pacific was the centre of origin of Balaenomorpha (crown mysticetes), Thalassotherii and Balaenoidea. The recurrent invasion of the Mediterranean by balaenomorph mysticetes occurred from both the North Atlantic and North Pacific.
Bisconti et al. 2020. A new species of rorqual whale (Cetacea, Mysticeti, Balaenopteridae) from the late Miocene of the southern North Sea basin and the role of the North Atlantic in the paleobiogeography of Archaebalaenoptera. PeerJ.
Link: https://peerj.com/articles/8315/
The rich fossil record of rorqual and humpback whales (Cetacea, Mysticeti, Balaenopteridae) is mainly characterized by monotypic genera since genera including more than one species are extremely rare. The discovery of new species belonging to known genera would be of great importance in order to better understand ancestor-descendant relationships and paleobiogeographic patterns in this diverse group. Recent discoveries in the southern North Sea Basin yielded a number of reasonably well preserved fossil balaenopterids from the Late Miocene; this sample includes a balaenopterid skull from Liessel, The Netherlands, which shares key characters with Archaebalaenoptera castriarquati from the Pliocene of Mediterranean. This skull is permanently held by Oertijdmuseum, Boxtel, The Netherlands, with the number MAB002286 and is investigated here.
A detailed comparative anatomical analysis of the skull MAB002286 is performed in order to understand its relationships. The age of the skull is determined by dinocyst analysis of the associated sediment. A paleobiogeographic analysis is performed to understand paleobiogeographic patterns within the balaenopterid clade the new skull belongs to.
Our work resulted in the description of Archaebalaenoptera liesselensis new species. The geological age of the holotype skull is between 8.1 and 7.5 Ma. The phylogenetic relationships of this species reveals that it is monophyletic with Archaebalaenoptera castriarquati from the Italian Pliocene. Moreover, in combination with a more basal species of Archaebalaenoptera from the late Miocene of Peru, our paleobiogeographic analysis suggests that the North Atlantic ocean played a major role as a center of origin of a number of balaenopterid clades including Protororqualus, Archaebalaenoptera and more advanced balaenopterid taxa. From a North Atlantic center of origin, two dispersal events are inferred that led to the origins of Archaebalaenoptera species in the South Pacific and Mediterranean. The distribution of Archaebalaenoptera was antitropical in the late Miocene. The role played by the Mediterranean salinity crisis is also investigated and discussed.
Bisconti et al. 2020. A natural endocast of an early Miocene odontocete and its implications in cetacean brain evolution. Journal of Comparative Neurology.
Link: https://onlinelibrary.wiley.com/doi/abs/10.1002/cne.25015
The natural endocast Museo di Geologia e Paleontologia of the Università degli Studi di Torino (MGPT)‐PU 13873 is described and analyzed in order to interpret its taxonomic affinities and its potential significance on our understanding of cetacean brain evolution. The endocast is from the early Miocene of Piedmont (between ca. 19 and 16 million years ago), Northwestern Italy, and shows a number of plesiomorphic characters. These include: scarcely rounded cerebral hemispheres, cerebellum exposed in dorsal view with little superimposition by the cerebral hemispheres, short temporal lobe, and long sylvian fissure. The distance between the hypophysis and the rostral pons is particularly high, as it was determined by the calculus of the hypothalamus quotient, suggesting that the development of a deep interpeduncular fossa was not as advanced as in living odontocetes. The encephalization quotient (EQ) of MGPT‐PU 13873 is ~1.81; therefore, this specimen shows an EQ in line with other fossil whales of the same geological age (early Miocene). Comparative analysis shows that there is a critical lack of data from the late Miocene and Pliocene that prevents us to fully understand the recent evolution of the EQ diversity in whales. Moreover, the past diversity of brain size and shape in mysticetes is virtually unknown. All these observations point to the need of additional efforts to uncover evolutionary patterns and processes on cetacean brain evolution.
Bisconti and Bosselaers 2020. A new balaenopterid species from the Southern North Sea Basin informs about phylogeny and taxonomy of Burtinopsis and Protororqualus (Cetacea, Mysticeti, Balaenopteridae). PeerJ.
Link: https://peerj.com/articles/9570/
An extensive radiation can be
inferred among balaenopterid mysticetes in the last 10 million years based on a
rich fossil record. Many extinct genera and species have been established in
the past by the study of fossil rorquals from northern and southern hemispheres.
In many cases, the new fossils are used to create new genera. However, in very
recent times, new species of known genera have been described that help our
understanding of the speciation processes and the biogeography of these whales.
Here, a new species of balaenopterid whales is described in order to better
understand the past diversity of Balaenopteridae and to analyze its
paleobiogeographical implications. As the new species closely resembles a taxon
established in the 19th century (i.e., Burtinopsis), a detailed
analysis of this taxon was necessary to support the new taxonomic statements of
this article.
A new partial skeleton including
skull and earbones is described and compared to an extended sample of living
and fossil mysticete species. A phylogenetic analysis including 355 character
states scored in 88 taxa was performed to understand its relationships within
the genus Protororqualus, to allow paleobiogeographic inferences
and to better understand the relationships of Protororqualus within
Balaenopteridae. Maximum parsimony analyses of character evolution were
performed to understand morphological transformations within Balaenopteridae.
The revision of Burtinopsis was carried out based on detailed
descriptions and comparisons of the type materials that were figured and
measured.
Protororqualus wilfriedneesi sp. nov. was established based on a comparative analysis of the skull and earbone morphology. The specimen is dated back to the Zanclean (Lower Pliocene, between c. 5.3 and 3.6 Ma). A taphonomical study of the holotype skeleton revealed evidence of interactions with sharks and fishes before the definitive burial of the carcass. Based on the phylogenetic analysis, the monophyly of the genus Protororqualus was confirmed. Protororqualus wilfriedneesi sp. nov. was more derived than Protororqualus cuvieri suggesting that it resulted from an invasion of the North Sea Basin (and the North Atlantic ocean) from the Mediterranean basin. Several specimens from western and eastern sides of the Atlantic Ocean are described that suggest that Protororqualus wilfriedneesi had a trans-Atlantic distribution in the Pliocene.
Comments: This is a pretty interesting paper as it reports specimens of this new species from both sides of the Atlantic. We've got these funky bullae with a triangular-ish anterior margin from the Pliocene of the Lee Creek Mine (and beyond) that I did not know how to identify - and they were referred to this new species of Protororqualus.
Modern whales and dolphins are superbly adapted for marine life, with tail flukes
being a key innovation shared by all extant species. Some dolphins can exceed speeds
of 50 km/h, a feat accomplished by thrusting the flukes while adjusting attack angle
with their flippers
. These movements are driven by robust axial musculature anchored to a relatively
rigid torso consisting of numerous short vertebrae, and controlled by hydrofoil-like
flippers. Eocene skeletons of whales illustrate the transition from semiaquatic to aquatic
locomotion, including development of a fusiform body and reduction of hindlimbs, but the rarity of Oligocene whale skeletons has hampered efforts to understand the evolution of fluke-powered, but forelimb-controlled,
locomotion. We report a nearly complete skeleton of the extinct large dolphin
Ankylorhiza tiedemani comb. n. from the Oligocene of South Carolina, previously known only from a partial
rostrum. Its forelimb is intermediate in morphology between stem cetaceans and extant
taxa, whereas its axial skeleton displays incipient rigidity at the base of the tail
with a flexible lumbar region. The position of
Ankylorhiza near the base of the odontocete radiation implies that several postcranial specializations
of extant cetaceans, including a shortened humerus, narrow peduncle, and loss of radial
tuberosity, evolved convergently in odontocetes and mysticetes. Craniodental morphology,
tooth wear, torso vertebral morphology, and body size all suggest that
Ankylorhiza was a macrophagous predator that could swim relatively fast, indicating that it was
one of the few extinct cetaceans to occupy a niche similar to that of killer whales.
Comments: Arguably my biggest accomplishment of 2020, and only first-authored research this year. This paper took three years of hard work to get finished, and I don't think I'll be submitting anything for a high profile journal again for some time. To read more about it on coastal paleo, read here and here.
Bosio et al. 2020. Mineralogical and geochemical characterization of fossil bones from a Miocene marine Konservat-Lagerstatte. Journal of South American Earth Sciences.
Link: https://www.sciencedirect.com/science/article/abs/pii/S0895981120304673
Fossil bones, together with teeth, are the most common remains of vertebrates that could manage to get preserved over geological times, providing information on the diagenetic and fossilization processes that occurred in the depositional paleoenvironment. Fossil bones from the marine vertebrate Konservat-Lagerstätte in the East Pisco Basin and Sacaco area (Peru) show a high variety of different textural and chemical features, suggestive of different processes variably contributing to the fossilization path. At the macroscopic scale, bone samples can be grouped into six different categories on the basis of the color (red to gray to white) and hardness (which relates to the mineralization degree); a variety of case studies can be found between these categories. Microscopically, the original microstructure of the bone tissue, both compact and cancellous, is well preserved in all the studied samples, with differences in cavity fillings, distribution of microcracks, and presence of Fe oxides in the diverse bone types. The bone composition and mineralogy correspond to fluorapatite. Differences in color, mineralization degree and geochemistry can be interpreted in terms of different fossilization paths, from burial at the seafloor to exposure in the present-day desert environment. The fossilization paths are strongly conditioned by the factors controlling the interplay of the mechanisms of apatite dissolution-recrystallization and dolomite precipitation (formation of carbonate concretions) as well as the fixation of iron in finely disseminated sulfides in the very early stages of fossilization.
Carone and Rizzo 2020. A new record of fossil sirenians from the Miocene of
The first diagnostic sirenian material from Sardinia is reported and the fossil record of Miocene Sardinian sirenians is reviewed through an updated geological and stratigraphic framework. The new specimens are referred to Metaxytherium cf. M. krahuletzi Deperet, 1895, indicating the diffusion of the species into the mid-southern Tethys. We also state that the other specimens from the earlymiddle Miocene previously found on the island should be assigned to the same species. We regard the holotype of Metaxytherium lovisati Capellini, 1886 as not diagnostic and consider it a nomen dubium. This conclusion is consistent with the taxonomic analysis given by Sorbi (2008) which winnowed the nominal taxa into four Miocene and Pliocene species.
Link: https://sciencepress.mnhn.fr/fr/periodiques/comptes-rendus-palevol/19/5
Nowadays, the odontocete family Kogiidae is monotypic and only includes two species of diminutive relatives of the great sperm whale Physeter Linnaeus, 1758. Conversely, a growing body of extinct species indicates that kogiids were diverse and disparate during the late Neogene. The fossil record of Kogiidae is, to date, represented by several cranial specimens from Mio-Pliocene localities of the Northern Hemisphere, with the significant Southern Hemisphere exception of the Pisco Formation of Peru, from which two genera were known so far, including Scaphokogia Muizon, 1988, a highly idiosyncratic form characterised by a distinctly spoon-shaped dorsal surface of the neurocranium and a downturned semicylindrical rostrum, which is even placed in its own subfamily Scaphokogiinae. Here, we report on two skulls of Kogiidae from the Messinian (upper Miocene) portion of the Pisco Formation exposed in the East Pisco Basin. These two skulls are referred to the new taxon Platyscaphokogia landinii n. gen., n. sp., which our phylogenetic analysis recovers as sister group of Scaphokogia, within the subfamily Scaphokogiinae. Although Platyscaphokogia n. gen. shares with Scaphokogia a remarkably spoon-like dorsal aspect of the neurocranium, it retains a non-pachyostotic, dorsoventrally thin rostrum that distinctly points anteriorly; as such, Platyscaphokogia n. gen. might be regarded as testifying an early stage in the evolution of the scaphokogiine cranial anatomy. Morphofunctional and palaeoecological considerations allow for hypothesising that Platyscaphokogia n. gen. was a raptorial physeteroid that foraged along the water column in relatively open-sea palaeoenvironments. In conclusion, our finds expand the palaeodiversity of Kogiidae, as well as our knowledge on the late Miocene sperm whales of the southeastern Pacific, and further suggest that the fossil content of the East Pisco Basin is crucial for reconstructing the Neogene evolutionary history of physeteroids.
Collareta et al. 2020. The shark-toothed dolphin Squalodon (Cetacea: Odontoceti) from the remarkable Montagna della Majella marine vertebrate assemblage (Bolognano Formation, central Italy). Carnets Geology.
Link: http://paleopolis.rediris.es/cg/20/02/index.html
The extinct family Squalodontidae consists of heterodont, medium-sized odontocetes, featuring a long rostrum that houses large, procumbent incisors and heavily ornamented postcanine teeth carrying accessory denticles, hence their vernacular name, "shark-toothed dolphins". These longirostrine toothed whales are often seen as bridging the anatomical gap between archaic Oligocene odontocetes and their late Miocene to Holocene relatives. Possibly among the major marine predators of their time, the shark-toothed dolphins are important components of several lower Miocene marine-mammal assemblages from the North Atlantic and Mediterranean/Paratethysian realms. In the present work, a partial skull of Squalodontidae is described from the strata of the Bolognano Formation cropping out in the northeastern sector of the Montagna della Majella massif (Abruzzo, central Italy), which has previously yielded a rich lower Miocene marine-vertebrate assemblage, including eleven taxa of elasmobranchs as well as subordinate teleosts and very fragmentary remains of marine reptiles and mammals. The specimen consists of the anterodorsal portion of a rostrum, preserving parts of both premaxillae and left maxilla, and the anteriormost seven upper left teeth. This partial skull is here identified as belonging to the genus Squalodon, whose presence in the Montagna della Majella vertebrate assemblage had already been tentatively proposed on the basis of two fragmentary teeth. The paleontological significance of this find is discussed in the broader framework of the Euromediterranean record of Squalodon.
Collaerta et al. 2020. On Leonardo and a fossil whale: a reappraisal with implications for the early history of palaeontology. Historical Biology.
A recent reappraisal of two passages in Leonardo da Vinci’s Codex Arundel, in which the then young Leonardo reports on visiting a cave and on some sort of ʽmarine monster’, has led to the proposition that Leonardo observed and wrote on fossil remains of a whale preserved in a cave. Whereas this hypothesis appears reasonable overall, some problems persist in accepting the purported location in which Leonardo would have observed the fossil. Here we provide a new analysis of the aforementioned passages by Leonardo which allows us to confirm that Leonardo saw a fossil whale and recognised it as such. However, his observation did not occur in a cave, but likely along the flank of a hill, as relatively common for Tuscan Pliocene fossil cetaceans. Leonardo seemingly made taphonomic observations on the fossil whale and inferred that a considerable amount of time must have passed from the death of the whale in the sea to allow for its eventual discovery on land – an observation that likely contributed to shaping Leonardo’s later thoughts on sedimentation and fossilisation. This might represent Leonardo’s earliest text devoted to a palaeontological theme. Moreover, it comprises the first known description of a cetacean fossil.
Coombs et al. 2020. Wonky whales: the evolution of cranial asymmetry in cetaceans. BMC Biology.
Link: https://bmcbiol.biomedcentral.com/articles/10.1186/s12915-020-00805-4
Unlike most mammals, toothed whale (Odontoceti) skulls lack symmetry in the
nasal and facial (nasofacial) region. This asymmetry is hypothesised to relate
to echolocation, which may have evolved in the earliest diverging odontocetes.
Early cetaceans (whales, dolphins, and porpoises) such as archaeocetes, namely
the protocetids and basilosaurids, have asymmetric rostra, but it is unclear
when nasofacial asymmetry evolved during the transition from archaeocetes to
modern whales. We used three-dimensional geometric morphometrics and
phylogenetic comparative methods to reconstruct the evolution of asymmetry in
the skulls of 162 living and extinct cetaceans over 50 million years.
In archaeocetes, we found asymmetry is prevalent in the rostrum and also in
the squamosal, jugal, and orbit, possibly reflecting preservational
deformation. Asymmetry in odontocetes is predominant in the nasofacial region.
Mysticetes (baleen whales) show symmetry similar to terrestrial artiodactyls
such as bovines. The first significant shift in asymmetry occurred in the stem
odontocete family Xenorophidae during the Early Oligocene. Further increases in
asymmetry occur in the physeteroids in the Late Oligocene, Squalodelphinidae
and Platanistidae in the Late Oligocene/Early Miocene, and in the Monodontidae
in the Late Miocene/Early Pliocene. Additional episodes of rapid change in
odontocete skull asymmetry were found in the Mid-Late Oligocene, a period of
rapid evolution and diversification. No high-probability increases or jumps in
asymmetry were found in mysticetes or archaeocetes. Unexpectedly, no increases
in asymmetry were recovered within the highly asymmetric ziphiids, which may
result from the extreme, asymmetric shape of premaxillary crests in these taxa
not being captured by landmarks alone.
Early ancestors of living whales had little cranial asymmetry and likely
were not able to echolocate. Archaeocetes display high levels of asymmetry in
the rostrum, potentially related to directional hearing, which is lost in early
neocetes—the taxon including the most recent common ancestor of living
cetaceans. Nasofacial asymmetry becomes a significant feature of Odontoceti
skulls in the Early Oligocene, reaching its highest levels in extant taxa.
Separate evolutionary regimes are reconstructed for odontocetes living in
acoustically complex environments, suggesting that these niches impose strong
selective pressure on echolocation ability and thus increased cranial asymmetry.
Davydenko et al. 2020. A small whale reveals diversity of the Eocene cetacean fauna of Antarctica. Antarctic Science.
Cetacean fossils have been recorded from middle and late Eocene deposits on Seymour Island since the beginning of the twentieth century and include fully aquatic Basilosauridae and stem Neoceti. Here, we report a small cetacean vertebra tentatively referred to as Neoceti from the late Eocene of Seymour Island. It shows a mosaic of traits, some of which are characteristic of early Neoceti (anteroposteriorly long transverse processes; a ventral keel on the ventral side of the centrum; thin pedicles of the neural arch), whereas others are shared with Basilosauridae (low-placed bases of the transverse processes). However, some traits are unique and may be autapomorphic: presence of separate prezygapophyses on the vertebra at the thoracic/lumbar boundary and a proportionally short centrum. Both traits imply a fast swimming style, which is characteristic of modern dolphins rather than Eocene cetaceans. Thus, this specimen can be identified as Neoceti indet., with some hypothetical odontocete affinities. Along with a few other Eocene whale taxa, it seems to be among the earliest known members of Neoceti on Earth. The finding of small and fast-swimming Neoceti in Antarctica also demonstrates early diversification of cetaceans and ecological niche partitioning by them dating back as early as the late Eocene.
Comments: Interesting paper that speculates perhaps beyond the bounds of the fossils. The ventral keel observation is a new one, but I might not be surprised if a small basilosaurid with this condition was discovered. A tantalizing find - but we'd need much more than this to confirm the existence of odontocetes in the Eocene. Ironically, this paper came just about a month or so after I updated my post on the Eocene origin of Neoceti and speculated that there is likely more to be found in Antarctica. I'll have to update it again...
Diaz-Berenguer et al. 2020. The hind limbs of Sobrarbesiren cardieli (Eocene, Northeastern Spain) and new insights into the locomotion capabilities of the quadrupedal sirenians. Journal of Mammalian Evolution.
Link: https://link.springer.com/article/10.1007/s10914-019-09482-9
In the transition from a terrestrial to an aquatic environment, sirenian marine mammals reduced and lost their hind limbs and developed a horizontal caudal fin, the main propulsive organ in extant sirenians. Quadrupedal forms are only known from the Eocene and are represented by three different clades: the amphibious “prorastomids,” the aquatic quadrupedal protosirenids, and Sobrarbesiren cardieli, a four-legged sirenian from the middle Eocene of Spain, considered the sister taxon of the fully aquatic Dugongidae. This ecological shift from terrestrial to an aquatic environment was naturally associated with adaptations, among others, of the skeleton. However, sirenian hind limb bones have been poorly studied because of the scarce material available in the fossil record. Here, we describe in detail the hind limb bones of Sobrarbesiren, analyzing their functional morphology and comparing them with other basal sirenians and cetaceans, and with related terrestrial mammals such as proboscideans and hyracoids. The hind limbs of Sobrarbesiren were capable of a great variety of movements. Based on the presence of a strong sacroiliac articulation, we propose that it swam by dorsoventral pelvic undulation combined with pelvic paddling analogous to extant otters and the “prorastomid” Pezosiren. We also conduct the first microanatomical analysis of hind limb bones of an Eocene sirenian. Data reveal extreme inner compactness in the Sobrarbesiren innominate and femur, with the first description of osteosclerosis in an amniote innominate combined with the highest degree of osteosclerosis observed in amniote femora. The results confirm that the microanatomical changes precede the external morphological changes in such ecological transitions. The process of adaptation of sirenians to an aquatic life was thus a more complex process than previously thought.
Gavazzi et al. 2020. Carpal morphology and function in the earliest cetaceans. Journal of Vertebrate Paleontology.
Link: https://www.tandfonline.com/doi/full/10.1080/02724634.2020.1833019
During the land-to-water transition in the Eocene epoch, the cetacean skeleton underwent modifications to accommodate life in the seas. These changes are well-documented in the fossil record. The forelimb transformed from a weight-bearing limb with mobile joints to a flipper with an immobile carpus. We used micro-CT imaging to assess evolutionary changes in carpal size, orientation, and articulation within Eocene cetacean taxa associated with the transition from a terrestrial to amphibious niche. We compared Ambulocetus natans, a well-preserved amphibious archaeocete, with other archaeocetes, and with Eocene terrestrial artiodactyls, the sister group to Cetacea. A cylindrical carpus in terrestrial taxa evolved into a mediolaterally flattened, cambered carpus in the semi-aquatic and fully aquatic cetaceans. Specifically, the pisiform bone shifted from a ventral orientation in terrestrial taxa to a lateral orientation, in plane with the carpus, within semi-aquatic and fully aquatic taxa. Flattening of the carpus, including lateral rotation of the pisiform, likely relates to functional shifts from weight-bearing terrestrial locomotion to aquatic locomotion. This laterally projecting pisiform morphology is retained in all extant cetaceans. Our results suggest this shift, along with other modifications to the carpus, predominantly occurred during the middle Eocene and facilitated an obligatorily aquatic lifestyle in late Eocene cetaceans.
Gol'din et al. 2020. The Volhynian (late middle Miocene) marine fishs and mammals as proxies for the onset of the eastern Paratethys recolonization by vertebrate fauna. Palaeontologia Electronica.
Link: https://palaeo-electronica.org/content/2020/3152-the-volhynian-late-middle-miocene
The late Middle Miocene of South-Eastern Europe was the time of major basin-wide physical and biogeographic transformations of marine environments with mass extinction and faunal replacement. We examined new material comprising marine fishes and mammals, re-examined earlier finds, and analysed previously published data on the marine vertebrate assemblage that lived along the western and northern edges of the Eastern Paratethys. The studied materials represent marine fishes that belong to at least four families (Clupeidae, Sparidae, Bothidae, and Scombridae), including Sarmatella doljeana, Sparus brusinai, Bothus parvulus, and indeterminate scombroids; true seals (Phocinae), the earliest seal record in the area; small toothed whales of the family Kentriodontidae, including Kentriodon fuchsii, whose presence in the Volhynian is confirmed here, and two other dwarf forms; a bizarre toothed whale Pachyacanthus, the first record in the area between the Vienna Basin and Central Asia; baleen whales, including an indeterminate member of the family Cetotheriidae, and “Archaeocetus fockii”. The material found so far hints to a low taxonomic diversity and biogeographical connections to both the synchronous Sarmatian fauna of the Central Paratethys and the later Bessarabian Eastern Paratethyan fauna. The taxonomic composition of the faunal assemblage and its biogeographical connections indicate that it has Central Paratethyan origin and shows an overall west to east direction of gradual dispersal, from the Central Paratethys through the Fore-Carpathian Basin and further east. The taxonomic composition of described Volhynian fish and mammal assemblages supports the idea of faunal connection and transition between the Central and Eastern Paratethys.
Hafed et al. 2020. Current status of pinnipeds phylogeny based on molecular and morphological data. Historical Biology.
Link: https://www.tandfonline.com/doi/full/10.1080/08912963.2020.1795649
The disagreement surrounding the relationship within pinnipeds as well as their phylogenetic affinities still remains unresolved. Molecular-based studies neglect significant morphological data and ignore the entire fossil record, which demonstrates why there are such contradicting results from morphology-based studies. There still remains a difference of opinion about the origin of pinnipeds, with research supporting origination from either Ursid (bear-like) or Mustelid (weasel-like) ancestors, even extending down to familial and subfamilial levels.
This study examines certain morphological characters in the three pinniped families: Otariidae (sea lions and fur seals), Odobenidae (walruses), and Phocidae (true seals), with extra emphasis on the four phocid subfamilies: Phocinae, Monachinae, Cystophorinae, and Devinophocinae. Morphological characters of the cranium (skull, dentition and mandible) and post cranium (humerus and femur) are the basis for understanding pinnipeds’ movement, body size, and sexual dimorphism, and all are ignored when only molecular analyses are used. Biomolecular based studies involve larger sample sizes and incorporate more phylogenetic characters, but ignore the significant data from the fossil record (which can only be examined through morphology). Therefore, the origin of pinnipeds cannot be resolved by depending only on molecular (genetic) or morphological approaches independently and future studies need to integrate both morphology and molecular data.
Hernandez Cisneros and Velez-Juarbe 2020. Palaeobiogeography of the North Pacific toothed mysticetes (Cetacea, Aetiocetidae): a key to Oligocene cetacean distributional patterns. Palaeontology.
Link: https://onlinelibrary.wiley.com/doi/abs/10.1111/pala.12507
Biogeographical distributional patterns of cetaceans reflect dispersal events and colonization of the oceans from their ancestral area in the ancient Sea of Tethys ̃53 Ma. Likewise, they reveal several vicariance events throughout the evolutionary history of this group. However, our understanding of how these processes took place and what biogeographical scenarios occurred among the different groups of cetaceans through time is limited. Consequently, this work focuses on explaining the distributional patterns of the well‐known North Pacific toothed mysticetes, Aetiocetidae, through the power of retrodiction offered by track analysis (panbiogeography) and cladistic biogeography, using the approach of evolutionary biogeography. Our results show that the distributional patterns of Aetiocetidae explain their endemism in the North Pacific, as well as indicating that their hypothetical ancestor probably colonized the Pacific from the Atlantic Ocean by a dispersal event (founder effect) via the Central American Seaway. Furthermore, their biogeographical history shows that the adaptive radiation (cladogenesis) of Aetiocetidae is result of peripatric speciation followed by sympatric speciation within a heterogeneous environment. Finally, the biogeographical framework of Aetiocetidae further supports the relevant role that the Pacific Ocean has played in the evolution of Oligocene cetaceans as a geographical area that promoted endemism, dispersal and colonization. At more local scales, environmental conditions further promoted increased diversity and disparity amongst Mysticeti.
Comments: A very interesting paper from our colleague Ehecatl Hernandez Cisneros, who stayed with our lab for a couple of months in New Zealand. My inability to learn Spanish severely hampered our discussions. I'm very glad to see another great article come out - and I expect more on his work with El Cien Formation Oligocene cetaceans in the future. This paper interprets the controversial toothed mysticete family Aetiocetidae as being biogeographically restricted to the North Pacific - which I believe based on the published fossil record. I've seen some unpublished things that might make me question this, but they don't count yet and besides, that's for someone else to demonstrate.
Kimura and Hasegawa 2020. Norisdelphis annakaensis, a new Miocene delphinid from Japan. Journal of Vertebrate Paleontology.
Link: https://www.tandfonline.com/doi/full/10.1080/02724634.2020.1762628
Two well-preserved delphinid crania have been recovered from the Haraichi Formation, Annaka Group, Gunma Prefecture, Japan (earliest late Miocene, Tortonian; 11.29–11.25 Ma). The specimens represent a new genus and species of delphinid, Norisdelphis annakaensis. The new species is characterized by transversely narrow and anteroposteriorly elongated external bony nares, and a wider proximal extremity of the left premaxilla. Phylogenetic analysis suggests that Norisdelphis is the most basal member of the Delphinidae. The previous oldest known described delphinid, Eodelphinus kabatensis, is from the upper Miocene (ca. 9 Ma), and other reliably dated and described fossil delphinids are no older than Pliocene; thus, N. annakaensis is the oldest convincingly dated and well-diagnosed fossil delphinid species yet described. Norisdelphis annakaensis expands the geological range of the family Delphinidae.
Comments: There's a well-preserved skull at LACM that was discovered in the Monterey Formation, and Larry Barnes published a couple of conference abstracts about it being the oldest known delphinid in the world. It's now on display upstairs in the mammal hall, and when I saw it in 2012, photographed it - it is indeed very similar, but has a less asymmetrical facial region - and may be congeneric with Norisdelphis.
Kimura et al. 2020. Fossil allodelphinids from the early Miocene Tomikusa Group, Arakida Formation, Nagano Prefecture, Japan. Bulletin of the Gunma Museum of Natural History.
Link: http://www.gmnh.pref.gunma.jp/research_no24
We describe four individuals of the fossil odontocetes from the lower Miocene Tomikusa Group, Nagano Prefecture, Japan. All the specimens were from the Arakida Formation. The geologic age of the upper part of Tomikusa Group (i.e., Arakida and Awano Formations) has been estimated as ca 18.1~17.2 Ma by magnetostratigraphy. The specimens represent the following combination of morphological characters and here we identify the specimens as Allodelphinidae gen. et sp. indet.: atlas vertebra bearing separate dorsal and ventral transverse process, and the vertebra is compressed dorsoventrally; the occipital condyles are large and they protrude prominently posteriorly.
Lambert et al. 2020. A new longirostrine sperm whale (Cetacea, Physeteroidea) from the lower Miocene of the Pisco Basin (southern coast of Peru). Journal of Systematic Palaeontology.
Link: https://www.tandfonline.com/doi/full/10.1080/14772019.2020.1805520
The modern sperm whales Kogia and Physeter (superfamily Physeteroidea) represent highly disparate, relict members of a group of odontocetes that peaked in diversity during the middle to late Miocene. Based on a highly informative specimen (including the cranium with ear bones, mandibles, teeth and some postcranial elements) from the lower Miocene (early Burdigalian, 19–18 Ma) of the Chilcatay Formation (Pisco Basin, Peru), we describe here a new genus and species of physeteroid, Rhaphicetus valenciae gen. et sp. nov. The latter is one of the geologically oldest physeteroids. This medium-sized species (estimated body length between 4.7 and 5.7 m) differs from all other physeteroids by the following, probably autapomorphic, features: a narrow, cylindrical rostrum comprising nearly 75% of the condylobasal length; the two main dorsal infraorbital foramina located posterior to the antorbital notch; an upper tooth count of at least 36 teeth per quadrant; and anterior-most upper alveoli filled by thick bony pads. Our phylogenetic analysis recovers R. valenciae as one of the earliest branching stem physeteroids. The highly unusual filling of the anterior upper alveoli by bony pads is interpreted as part of a mechanism leading to the loss of apical and subapical upper teeth. By comparison with other odontocetes displaying some degree of anterior reduction of the dentition, this condition may have corresponded to the rostrum being anteriorly longer than the mandible. The elongated rostrum with a circular cross-section, the long temporal fossa, and the high number of slender, pointed upper and lower teeth all suggest that R. valenciae used its dentition to grasp relatively small prey, possibly via rapid movements of the head. On the one hand, this new Peruvian record increases our knowledge of the morphological disparity of sperm whales during the Miocene. On the other hand, it may provide clues to the ancestral morphotype for all physeteroids.
Lambert et al. 2020. A new small, mesorostrine inioid (Cetacea, Odontoceti, Delphinida) from four upper Miocene localities in the Pisco Basin, Peru. Papers in Palaeontology.
Link: https://onlinelibrary.wiley.com/doi/abs/10.1002/spp2.1332
The moderately rich past diversity of the superfamily Inioidea (Cetacea, Odontoceti) in both the Atlantic and Pacific oceans contrasts with the present survival of a single genus (Inia, Amazon river dolphin, family Iniidae) in freshwater deposits of South America and of a single species (Pontoporia blainvillei, franciscana, family Pontoporiidae) along the eastern coast of that continent. However, part of the late Miocene – Pliocene inioid fossil record consists of relatively fragmentarily known species, for which systematic affinities remain poorly understood. Based on a sample of six cranial specimens from lower upper Miocene (Tortonian, 9.5–8.6 Ma) marine deposits of the Pisco Formation exposed at four localities of the East Pisco Basin (southern coast of Peru), we describe a new genus and species of inioid, Samaydelphis chacaltanae. This mesorostrine, small‐sized species is characterized by an upper tooth count of c. 30 teeth per row, a moderately elevated vertex of the cranium displaying a long anteromedial projection of the frontals and interparietal, and the plesiomorphic retention of a premaxilla–nasal contact. Recovered as a member of the family Pontoporiidae in our phylogenetic analysis, S. chacaltanae falls as sister group to Meherrinia isoni, from the upper Miocene of North Carolina (USA), which has previously been tentatively referred to the Iniidae or regarded as a stem Inioidea. Originating from the P1 allomember of the Pisco Formation, the mesorostrine S. chacaltanae was contemporaneous and sympatric with two other inioids, the brevirostrine pontoporiid Brachydelphis mazeasi and the longirostrine iniid Brujadelphis ankylorostris.
de Lavigerie et al. 2020. New Pliocene right whale from Belgium informs balaenid phylogeny and function. Journal of Systematic Palaeontology.
Link: https://www.tandfonline.com/doi/abs/10.1080/14772019.2020.1746422
Right whales (Balaenidae) are the most distinctive family of extant baleen whales, thanks to their highly arched rostrum, tall lips and robust body shape. They are also the oldest, originating as much as 20 million years ago (Ma). Nevertheless, their fossil record is patchy and frequently understudied, obscuring their evolution. Here, we describe a new stem balaenid, Antwerpibalaena liberatlas, from northern Belgium, adding to the rich but historically problematic baleen whale assemblage of the Pliocene North Sea. Within right whales, Antwerpibalaena forms a clade with two previously described extinct genera, Balaenella and Balaenula. The holotype preserves much of the postcranial skeleton, and informs the emergence of typical balaenid traits like fused neck vertebrae and paddle-shaped flippers. Its size is intermediate between that of extant right whales and most of their extinct forebears revealing a more complex pattern of balaenid size evolution than previously thought.
Comments: This is one of two papers fundamentally altering the state of balaenid (right whale) paleontology. Antwerpibalaena, five years ago, would've just been called Balaenula - the monophyly of which some folks have rightly been skeptical of. Interestingly is that this taxon has a free atlas - most balaenids have fused all seven cervicals together, but the atlas is still free here - a bit like a sperm whale. This further indicates that the six v. seven rule is no longer useful for identifying fragmentary, poorly preserved syncervical specimens. This was published within 24 hours of the paper on Archaeobalaena, which felt like a Twilight Zone episode.
Montanez-Rivera and Hampe. 2020. An unfamiliar physeteroid periotic (Cetacea: Odontoceti from the German middle-late Miocene North Sea basin at Groß Pampau. Fossil Record.
Link: https://fr.copernicus.org/articles/23/151/2020/
The Miocene mica clay locality of Groß Pampau, known for numerous and partly spectacular finds of marine mammals is becoming more and more a prominent site that bears the potential to resolve questions regarding taphonomic relationships and to interpret life communities of the ancient North Sea because of its rich faunal assemblage including invertebrates and other remains of various vertebrate organisms. In the present work we describe a right periotic of Physeteroidea with morphological characters so far unknown from other sperm whales. The periotics of the middle Miocene Aulophyseter morricei demonstrate the closest resemblance to the Groß Pampau specimen in their overall appearance and in the general arrangement and proportions of single structures, particularly of the anterior process and pars cochlearis. A great similarity is also documented with periotics of the living sperm whale, Physeter macrocephalus, especially regarding the shape and disposition of the anterior process and the bony element located dorsally to the accessory ossicle. Kogiid periotics differ strongly from that of the Groß Pampau specimen by having an inflated and short anterior process and, typically, three well-defined spines on it. A new taxonomic naming of the Groß Pampau periotic is not appropriate at this stage, although it might demonstrate the existence of a so-far undescribed physeteroid species. Additionally, its systematic position remains yet unclear and it is unknown at this point if it could belong to Hoplocetus ritzi, another physeterid, whose fragments were discovered in the same locality, or to another, already-described taxon, of which the periotic is still unknown.
Nelson et al. 2020. A new platanistoid, Perditicetus yaconensis gen et sp. nov. (Cetacea, Odontoceti) from the Chattian-Aquitanian Nye Formation of Oregon. Journal of Systematic Palaeontology.
Link: https://www.tandfonline.com/doi/full/10.1080/14772019.2020.1783379
The Platanistoidea is a large superfamily of odontocetes whose sole surviving member is Platanista gangetica, the Ganges river dolphin. Despite the diversity of the Platanistoidea, it remains poorly understood and in need of revision. As one of the earliest-diverging clade of crown odontocetes, understanding their distribution, morphology, and phylogeny is crucial to understanding the radiation of archaic odontocetes in the late Oligocene to the middle Miocene. Here we describe an archaic odontocete, named Perditicetus yaconensis, gen. et. sp. nov., from the latest Oligocene–earliest Miocene Nye Formation in Oregon. Perditicetus yaconensis, represented by the holotype USNM 335224, possesses several synapomorphies of the Platanistoidea. Intriguingly, strong morphological similarities exist between P. yaconensis and other archaic odontocetes in the ‘Chilcacetus clade’ especially in the vertex and pterygoid region. However, the results of our phylogenetic analyses failed to capture any phylogenetic relationships between Perditicetus and Chilcacetus. In this analysis, P. yaconensis is sister taxon to the clade Allodelphinidae + Squalodelphinidae + Platanistidae and we consider that P. yaconensis is one of the basal-most derived platanistoids. The type locality of the holotype specimen, in the Nye Formation, provides a window into the diversity of archaic odontocetes, especially platanistoids, during the latest Oligocene to earliest Miocene.
Paterson et al. 2020. A total evidence phylogenetic analysis of pinniped phylogeny and the possibility of parallel evolution within a monophyletic framework. Frontiers in Ecology and Evolution.
Link: https://www.frontiersin.org/articles/10.3389/fevo.2019.00457/full
In the present study, a series of phylogenetic analyses of morphological, molecular, and combined morphological-molecular datasets were conducted to investigate the relationships of 23 extant and 44 fossil caniforme genera, in order to test the phylogenetic position of putative stem pinniped Puijila within a comprehensive evolutionary framework. With Canis as an outgroup, a Bayesian Inference analysis employing tip-dating of a combined molecular-morphological (i.e., Total Evidence) dataset recovered a topology in which musteloids are the sister group to a monophyletic pinniped clade, to the exclusion of ursids, and recovered Puijila and Potamotherium along the stem of Pinnipedia. A similar topology was recovered in a parsimony analysis of the same dataset. These results suggest the pinniped stem may be expanded to include additional fossil arctoid taxa, including Puijila, Potamotherium, and Kolponomos. The tip-dating analysis suggested a divergence time between pinnipeds and musteloids of ~45.16 million years ago (Ma), though a basal split between otarioids and phocids is not estimated to occur until ~26.52 Ma. These results provide further support for prolonged freshwater and nearshore phases in the evolution of pinnipeds, prior to the evolution of the extreme level of aquatic adaptation displayed by extant taxa. Ancestral character state reconstruction was used to investigate character evolution, to determine the frequency of reversals and parallelisms characterizing the three extant clades within Pinnipedia. Although the phylogenetic analyses did not directly provide any evidence of parallel evolution within the pinniped extant families, it is apparent from the inspection of previously-proposed pinniped synapomorphies, within the context of a molecular-based phylogenetic framework, that many traits shared between extant pinnipeds have arisen independently in the three clades. Notably, those traits relating to homodonty and limb-bone specialization for aquatic locomotion appear to have multiple origins within the crown group, as suggested by the retention of the plesiomorphic conditions in early-diverging fossil members of the three extant families. Thus, while the present analysis identifies a new suite of morphological synapomorphies for Pinnipedia, the frequency of reversals and other homoplasies within the clade limit their diagnostic value.
Comments: I've been waiting for this paper for a couple years - and a paper like it for nearly a decade. The most critical thing is that this paper does support the idea that Puijila - the "walking seal" - is related to pinnipeds, and Potamotherium with it. It also supports a similar relationship with Kolponomos - the "oyster bear". However, in the analysis, Kolponomos is reconstructed as nested within Enaliarctos - which can't be right. Species of Enaliarctos are remarkably consistent in skull morphology and mostly distinguished from each other by minor changes in dental features. I think some of the details are a bit muddled, and likely would benefit from some double checking of character codings in the matrix, but on the whole I think it really moves pinniped paleontology forward. I'm also particularly smug about the findings with Kolponomos as an early pinniped relative or sister taxon as I predicted that it would be recovered there if Puijila and Potamotherium were found to be early pinnipeds, since they share some of the same pinniped-like features.
Paolucci et al. 2020. 'Aulophyseter' rionegrensis (Cetacea: Odontoceti: Physeteroidea) from the Miocene of Patagona (Argentina): a reappraisal. Zoological Journal of the Linnean Society.
Link: https://academic.oup.com/zoolinnean/advance-article-abstract/doi/10.1093/zoolinnean/zlaa137/6030877
The giant sperm whale (Physeter macrocephalus) and the dwarf (Kogia sima) and pygmy (Kogia breviceps) sperm whales represent the only three extant species of physeteroids. This group has diversified during the Miocene, and the Miocene marine sediments of Patagonia (Argentina) hold one of the most important fossil records of physeteroids. In particular, ‘Aulophyseter’ rionegrensis (Gran Bajo del Gualicho Formation, Miocene), described based on two subcomplete skulls nearly a century ago, has been a problematic taxon because its generic assignation has been questioned in different works. Besides, recent phylogenetic analyses have also failed to recover the putative congeneric sister-group relationship between ‘A.’ rionegrensis and A. morricei (the type species). In this contribution, we re-describe ‘A.’ rionegrensis, evaluate its phylogenetic position and provide a taxonomic review of Aulophyseter. A detailed morphological comparison between ‘A.’ rionegrensis and A. morricei reveals several anatomical differences between them. Phylogenetic analyses recover ‘A.’ rionegrensis as a crown physeteroid, nested within Physeteridae, but not closely related to A. morricei. We provide the new generic name Cozzuoliphyseter gen. nov. for its reception. A preliminary re-assessment of material previously referred to Aulophyseter indicates that A. mediatlanticus, and also historical material of A. morricei, need to be reviewed.
Peri et al. 2020. A new record of Physeteroidea from the upper Miocene of the Pietra Leccese (Southern Italy): systematics, paleoecology, and taphonomy of a fossil macroraptorial sperm whale. Rivista Italiana di Paleontologia e Stratigrafia.
Link: https://riviste.unimi.it/index.php/RIPS/article/view/14284
We report on a partial skeleton of sperm whale (Cetacea, Odontoceti, Physeteroidea) from the Pietra leccese, a Miocene limestone widely exposed in the Salento Peninsula (southern Italy). This specimen was found in Tortonian strata cropping out at the Cisterna quarry, not far from the holotype of the stem physeteroid Zygophyster varolai. The presence of a deep and rectilinear groove medial to the tympanosquamosal recess of the squamosal, the bowed mandibles, and some dental features suggest that this specimen belongs to a still undescribed new genus and species of macroraptorial sperm whale that displays some affinities with the late Miocene Acrophyseter from Peru. Nevertheless, due to the incompleteness and poor preservation state of the skull, we abstain from creating a new taxon. The teeth exhibit both apical wear and deep occlusal facets, and three teeth even lost their crowns. These dental modifications suggest that the studied specimen used a raptorial feeding strategy for preying upon food items such as large-sized bony fishes or diminutive marine mammals. The bones are mostly disarticulated and broken, and some of them preserve traces hinting at the action of macro-scavengers, possibly including both sharks and bony fishes. Furthermore, the skull is pervasively encrusted by oysters, which suggests that it laid on the seafloor for a long time before being buried. This find provides new clues about the composition of the Miocene vertebrate assemblage of the Pietra leccese and indicates that various macroraptorial sperm whale species inhabited the Mediterranean Basin during the Tortonian.
Perini et al. 2020. A new species of Trichechus Linnaeus, 1758 (Sirenia, Trichechidae), from the upper Pleistocene of southwestern Amazonia, and the evolution of Amazonian manatees. Journal of Vertebrate Paleontology.
Link: https://www.tandfonline.com/doi/full/10.1080/02724634.2019.1697882
The genus Trichechus (Mammalia, Sirenia, Trichechidae) harbors a modest diversity, comprising only three living species of manatees, and no species currently recognized as fossil. Herein, we report a new extinct species of manatee from the late Pleistocene of the Brazilian Amazonia, Trichechus hesperamazonicus, sp. nov. It comes from the alluvial deposits of the Rio Madeira Formation along the Madeira River, state of Rondônia, western Brazil, and is represented by a partial palate with both molar series and two partial right dentaries. The new taxon shows a mosaic of characteristics resembling those of other manatee species, as well as some unique characters. It differs from all other Trichechus species by possessing a wide space between the posterior lower tooth row and ascending ramus of dentary, and by having the anterior border of the ascending ramus covering the posterior end of the tooth row in lateral view. The results of morphometric analyses (principal component analysis and discriminant analysis) further support the distinctiveness of the new species. A phylogenetic analysis recovers the new species in a polytomy with T. inunguis and the clade formed by T. senegalensis and T. manatus. The levels from which the remains were recovered produced a radiocarbon date of 44,710 ± 880 years before present; together with molecular clock estimates, this date suggests that until recently at least two species of manatees coexisted in the fluvial systems of western Amazonia.
Rule et al. 2020. First monk seal from the southern hemisphere rewrites the evolutionary history of true seals. Proceedings B.
Link: https://royalsocietypublishing.org/doi/10.1098/rspb.2020.2318
Living true seals (phocids) are the most widely dispersed semi-aquatic marine mammals, and comprise geographically separate northern (phocine) and southern (monachine) groups. Both are thought to have evolved in the North Atlantic, with only two monachine lineages—elephant seals and lobodontins—subsequently crossing the equator. The third and most basal monachine tribe, the monk seals, have hitherto been interpreted as exclusively northern and (sub)tropical throughout their entire history. Here, we describe a new species of extinct monk seal from the Pliocene of New Zealand, the first of its kind from the Southern Hemisphere, based on one of the best-preserved and richest samples of seal fossils worldwide. This unanticipated discovery reveals that all three monachine tribes once coexisted south of the equator, and forces a profound revision of their evolutionary history: rather than primarily diversifying in the North Atlantic, monachines largely evolved in the Southern Hemisphere, and from this southern cradle later reinvaded the north. Our results suggest that true seals crossed the equator over eight times in their history. Overall, they more than double the age of the north–south dichotomy characterizing living true seals and confirms a surprisingly recent major change in southern phocid diversity.
Comments: I actually saw some of these specimens while they remained in private collections in New Zealand. These are all found in concretions - and one of the only phocid-bearing fossil assemblages in the world to be preserved in nodules. We have a serious problem with headless phocid taxa in the fossil record - very few fossil phocids are known from skulls, and most are known either only from a mandible or postcrania, especially from the North Atlantic, where the record is numerically richest - with a couple of exceptions. The situation in Peru is very different since skeletons are often found out in the desert and can be excavated carefully. For some reason, the skulls of North Atlantic specimens both on the east coast and the low countries in Europe are always fractured prior to discovery and tend to be very fragmentary. Anyway, this paper reports some fantastically preserved specimens of the extinct monk seal Eomonachus from New Zealand - and demonstrates that even the monachines must have undergone a period of southern hemisphere evolution.
Rule et al. 2020. A new large-bodied Pliocene seal with unusual cutting teeth. Royal Society Open Science.
Link: https://royalsocietypublishing.org/doi/10.1098/rsos.201591
Today, monachine seals display the largest body sizes in pinnipeds. However, the evolution of larger body sizes has been difficult to assess due to the murky taxonomic status of fossil seals, including fossils referred to Callophoca obscura, a species thought to be present on both sides of the North Atlantic during the Neogene. Several studies have recently called into question the taxonomic validity of these fossils, especially those from the USA, as the fragmentary lectotype specimen from Belgium is of dubious diagnostic value. We find that the lectotype isolated humerus of C. obscura is too uninformative; thus, we designate C. obscura as a nomen dubium. More complete cranial and postcranial specimens from the Pliocene Yorktown Formation are described as a new taxon, Sarcodectes magnus. The cranial specimens display adaptations towards an enhanced ability to cut or chew prey that are unique within Phocidae, and estimates indicate S. magnus to be around 2.83 m in length. A parsimony phylogenetic analysis found S. magnus is a crown monachine. An ancestral state estimation of body length indicates that monachines did not have a remarkable size increase until the evolution of the lobodontins and miroungins.
Rule et al. 2020. Colonization of the ancient southern oceans by small-sized Phocidae: new evidence from Australia. Zoological Journal of the Linnean Society.
Most of the diversity of extant southern true seals (Phocidae: Monachinae) is present in the Southern Ocean, but a poor fossil record means that the origin of this fauna remains unknown. Australia represents a large gap in the record bordering the Southern Ocean that could possibly inform on the origins of the extant Antarctic monachines, with most known fossils remaining undescribed. Here we describe the oldest Australian fossil pinniped assemblage, from the Late Miocene to the Early Pliocene of Beaumaris. Two fossils are referrable to Pinnipedia, five (possibly six) to Phocidae and a humerus is referrable to Monachinae. The humerus is not referrable to any extant tribe, potentially representing an archaic monachine. The description of this assemblage is consistent with the Neogene pinniped fauna of Australia being exclusively monachine before the arrival of otariids (fur seals and sea lions). The Beaumaris humerus, along with other Neogene phocids from the Southern Ocean margins, were smaller than their extant Antarctic relatives, possibly driven by longer food chains with less energy efficiency between trophic levels. This suggests that small archaic phocids potentially used the Southern Ocean as a means of dispersal before the arrival of extant Antarctic monachines.
Rule et al. 2020. Pliocene monachine seal (Pinnipedia: Phocidae) from Australia constrains timing of pinniped turnover in the southern hemisphere. Journal of Vertebrate Paleontology.
Link: https://www.tandfonline.com/doi/full/10.1080/02724634.2019.1734015
A turnover of the pinniped fauna took place in the Southern Hemisphere during the Pliocene, based on evidence from South America and South Africa. This resulted in the extinction of early phocids, which were replaced by otariids dispersing from the North Pacific. There is currently a lack of evidence of a similar event from Australia, with the only confirmed phocids from the Miocene–Pliocene boundary and the earliest confirmed otariids from the late Pleistocene. Here, we report a fossil monachine tooth from the Pliocene Whalers Bluff Formation of Portland (Victoria). The tooth represents an extinct monachine seal; it does not resemble either crown lobodontins or miroungins. This is the geologically youngest pre-Holocene occurrence of Phocidae in Australia, and one of the youngest pre-Pleistocene records of phocids in the Southern Hemisphere. It extends the maximum known geochronological range of monachines in the fossil record of Australia to between 6.2 and 2.67 Ma. It is possible that pinniped faunal turnovers in the Southern Hemisphere all occurred during the late Pliocene, with the turnover in Australia occurring sometime after 4.31 Ma. The description of additional Australasian fossil pinnipeds will further constrain this faunal turnover event.
Shinmura and Kimura. 2020. Digital 3D model of natural history museum specimens and its application: creating an illustration of the Kentriodon nakajimai (Odontoceti, Kentriodontidae). Bulletin of the Gunma Museum of Natural History.
Link: http://www.gmnh.pref.gunma.jp/research_no24
[no english abstract]
Tanaka et al. 2020. A new member of fossil balaenid (Mysticeti, Cetacea) from the early Pliocene of Hokkaido, Japan. Royal Society Open Science.
Link: https://royalsocietypublishing.org/doi/10.1098/rsos.192182
The family Balaenidae includes two genus and four extant species. Extinct balaenids are known for at least four genus and 10 species. The oldest known record of members of the Balaenidae is known from the early Miocene, but still need more early members of the family to provide better phylogenetic hypotheses. FCCP 1049 from the lower part of the Chippubetsu Formation, Fukagawa Group (3.5–5.2 Ma, Zanclean, early Pliocene) was preliminary described and identified as Balaenula sp. by Furusawa and Kimura in 1982. Later works discussed that FCCP 1049 is different from the genus, and is placed in different clade from Balaenula astensis. The result of our phylogenetic analysis places FCCP 1049 basal to Balaenella brachyrhynus, and is again separated from B. astensis. In this study, FCCP 1049 is re-described and named as Archaeobalaena dosanko gen. et sp. nov. Archaeobalaena dosanko is distinguishable from other balaenids by having a deep promontorial groove of the pars cochlearis of the periotic. Archaeobalaena dosanko can be differentiated from other balaenids, except Morenocetus parvus by having a slender zygomatic process, and posteriorly oriented postorbital process in dorsal view. Archaeobalaena dosanko adds detailed skull, periotic and bulla morphologies for the earlier balaenids.
Comments: The paper that broke the camel's back - and by camel, I mean Balaenula, the extinct dwarf right whale. Archaeobalaena was named off of a partial skull that had been under study for a couple of decades, and I am relieved to finally see it published. This was long known as the "Japanese Balaenula" but now appears to sit in a different phylogenetic position as a stem Balaenid, complicating identification of small balaenids in the fossil record. This paper was published within 24 hours of the paper on Antwerpibalaena, which was quite strange!
Tanaka et al. 2020. A new skull of an early diverging rorqual (Balaenopteridae, Mysticeti, Cetacea) from the late Miocene to early Pliocene of Yamagata, northeastern Japan. Palaeontologia Electronica.
Link: https://palaeo-electronica.org/content/2020/2943-fossil-rorqual-from-japan
The family of rorquals and humpback whales, Balaenopteridae includes the largest living animal on Earth, the blue whale Balaenoptera musculus. Many new taxa have been named, but not many from the western Pacific, except Miobalaenoptera numataensis from Japan. Here we describe an early balaenopterid, cf. M. numataensis from a late Miocene to early Pliocene sediment in Yamagata Prefecture, northeastern Japan. The species has a straight and sharp lateral ridge of the fovea epitubaria at the ventral surface of the periotic, and a dorsoventrally thin pars cochlearis. The new specimen provides knowledge of supposed ontogenetic variation and periotic morphology in poorly known fossil balaenopterids.
Tate-Jones and Peredo. 2020. The dawn of Desmatophocidae: a new species of basal desmatophocid seal (Mammalia, Carnivora) from the Miocene of Oregon, USA. Journal of Vertebrate Paleontology.
Link: https://www.tandfonline.com/doi/full/10.1080/02724634.2020.1789867
Desmatophocidae (Mammalia, Carnivora) represents the first of the four major pinniped clades to appear in the fossil record. However, the majority of its known diversity consists of derived species and little is known about the nascence of this early pinniped lineage. Here we report the discovery of Eodesmus condoni, gen. et sp. nov., represented by a nearly complete cranium from the Burdigalian Iron Mountain Bed of the Astoria Formation from the central coast of Oregon, U.S.A. Notably, this specimen possesses nasolabialis fossae, a plesiomorphic trait shared with stem pinnipedimorphs and the basal phocid Devinophoca sp., but not with any other desmatophocid. Phylogenetic analysis (98 characters, 27 taxa) resolved Eodesmus condoni as the most basal desmatophocid yet described. Poor support for the monophyly of Otarioidea, Odobenidae, and Phocoidea demonstrate that high-level relationships within Pinnipedia have yet to be conclusively resolved. The identification of another desmatophocid species at the already pinniped-rich Iron Mountain Bed suggests that the approximately synchronous mid-Miocene Climatic Optimum played a role in this increase in pinnipedimorph species diversity.
Tonomori et al. 2020. Large-sized cetacean fossils from Tonohama Group in the Iwado area, Muroto City, Kochi Prefecture, Japan. Bulletin of the National Museum of Natural Sciences Series C.
Link: https://www.kahaku.go.jp/english/research/publication/geology/v46.html
Two cetacean specimens (humerus and lumber vertebrae) derived from the latest Miocene to early Pliocene shallow marine deposit (ca. 5.6–3.8 Ma) in the Iwado area, Muroto City, Kochi Prefecture, Shikoku, Japan, are reported. Owing to the partially preserved state of the specimens, it is difficult to identify them even at the suborder level. However, on the basis of their morphological features and a comparison of extant cetaceans, the humerus specimen was derived from a large-sized (11 to 15 m) cetacean and the lumbers also as large as, or larger medium-sized (4 to 10 m) cetacean, indicating both specimens of whale-sized cetacean provenance. This is the first report of large-sized cetacean fossil from Shikoku. At present, some species of large-sized cetaceans inhabit offshore waters around Kochi (e.g., Eden's whale (Balaenoptera edeni) in Tosa Bay). Therefore, this study indicates that large-sized cetaceans have lived in the area since at least the early Pliocene (Zanclean: ca. 3.8 Ma). Although the divergence of cetaceans in Japanese waters during the middle Miocene to Pliocene is considered to be associated with the development of the Kuroshio Current, which flows along the southern coast of Japan with its northern limit being located off the coast of the Boso Peninsula in Chiba Prefecture, this is only supported by fossil fauna from limited areas: the Kakegawa fauna of Okinawa Pref., southernmost Japan. This study indicates that the distribution of cetaceans around the southern coast of Japan was more extensive along the Kuroshio Current during the late Miocene to Pliocene.
Tsai et al. 2020. A Pliocene gray whale (Eschrichtius sp.) from the eastern North Atlantic. Rivista Italiana di Paleontologia e Stratigrafia.
Link: https://riviste.unimi.it/index.php/RIPS/article/view/13040
The gray whale Eschrichtius robustus, the only living member of the eschrichtiid lineage, currently inhabits only the North Pacific. Interestingly, however, the holotypes of both E. robustus and the late Miocene Archaeschrichtius ruggieroi (the oldest known eschrichtiid species) come from the North Atlantic and the Mediterranean, respectively. Here we describe a partial mysticete mandible from the Pliocene (3.71–2.76 Ma) of Belgium (Eastern North Atlantic). This new fossil displays a combination of morphological features that makes it nearly identical to modern E. robustus. Nevertheless, given its incomplete nature, the studied specimen is here identified in open nomenclature as belonging to Eschrichtius sp. The recognition of such an early record of Eschrichtius in the North Atlantic suggests that this genus developed a circum-Northern Hemisphere distribution not later than in Pliocene times, thus complicating our understanding of its origin, evolutionary history, and palaeobiogeographic patterns.
Tzuzuku and Kohno. 2020. The oldest record of the Steller sea lion Eumetopias jubatus (Scheber, 1776) from the early Pleistocene of the North Pacific. PeerJ.
Link: https://peerj.com/articles/9709/
The extant genera of fur seals and sea lions of the family Otariidae (Carnivora: Pinnipedia) are thought to have emerged in the Pliocene or the early Pleistocene in the North Pacific. Among them, the Steller sea lion (Eumetopias jubatus) is the largest and distributed both in the western and eastern North Pacific. In contrast to the limited distribution of the current population around the Japanese Islands that is now only along the coast of Hokkaido, their fossil records have been known from the middle and late Pleistocene of Honshu Island. One such important fossil specimen has been recorded from the upper lower Pleistocene Omma Formation (ca. 1.36–0.83 Ma) in Kanazawa, Ishikawa Prefecture, Japan, which now bears the institutional number GKZ-N 00001. Because GKZ-N 00001 is the earliest fossil having been identified as a species of the sea lion genus Eumetopias, it is of importance to elucidate the evolutionary history of that genus. The morphometric comparisons were made among 51 mandibles of fur seals and sea lions with GKZ-N 00001. As results of bivariate analyses and PCA based on 39 measurements for external morphologies with internal structures by CT scan data, there is almost no difference between GKZ-N 00001 and extant male individuals of E. jubatus. In this regard, GKZ-N 00001 is identified specifically as the Steller sea lion E. jubatus. Consequently, it is recognized as the oldest Steller sea lion in the North Pacific. About 0.8 Ma, the distribution of the Steller sea lion had been already established at least in the Japan Sea side of the western North Pacific.
Uhen and Taylor 2020. A basilosaurid archaeocete (Cetacea, Pelagiceti) from the late Eocene of Oregon, USA. PeerJ.
Link: https://peerj.com/articles/9809/
Basilosaurid archaeocetes are known from the Late Eocene of virtually all coastlines bearing coeval marine rocks except the North Pacific Basin, until now. Here we report on three consecutive posterior thoracic vertebrae of a large, basilosaurid archaeocete from a Late Eocene horizon in the Keasey Formation in Oregon.
These vertebrae were morphologically and morphometrically compared to other vertebrae of similar age from around the world.
The specimens were determined to be different from all currently named species of fossil cetacean, but most similar to those found in the Gulf Coast region of North America. These vertebrae represent the first confirmed specimen of a Late Eocene basilosaurid from the North Pacific. These and other basilosaurids known only from vertebrae are reviewed here in the context of Late Eocene paleoceanography and cetacean evolution.
Comments: Finally! Kellogg reported a basilosaurid like vertebra from Vancouver Island back in the 30s, but it was subsequently reidentified as a mysticete based on its Oligocene age. There aren't a whole lot of vertebrate-bearing Eocene rock units on the west coast - and those in the Pacific Northwest are generally deep water, so fossils are very few and far between, and poorly exposed (e.g. cliffs along rivers and creeks, and occasional coastal cliffs). It's about damn time.
Valenzuela-Toro and Pyenson. 2020. Extreme dispersal of human transport? The enigmatic case of an extralimital freshwater occurrence of a southern elephant seal from Indiana. PeerJ.
Link: https://peerj.com/articles/9665/
Elephant seals (Mirounga spp.) are the largest living pinnipeds, and the spatial scales of their ecology, with dives over 1 km in depth and foraging trips over 10,000 km long, are unrivalled by their near relatives. Here we report the discovery of an incomplete Holocene age Southern elephant seal (M. leonina) rostrum from Indiana, USA. The surviving material are two casts of the original specimen, which was collected in a construction excavation close to the Wabash River near Lafayette, Indiana. The original specimen was mostly destroyed for radiometric dating analyses in the 1970s, which resulted in an age of 1,260 ± 90 years before the present. The existence of sediments in the original specimen suggests some type of post depositional fluvial transportation. The prevalent evidence suggests that this male Southern elephant seal crossed the equator and the Gulf of Mexico, and then entered the Mississippi River system, stranding far upriver in Indiana or adjacent areas, similar to other reported examples of lost marine mammals in freshwater systems. Based on potential cut marks, we cannot exclude human-mediated transportation or scavenging by Indigenous peoples as a contributing factor of this occurrence. The material reported here represents by far the northernmost occurrence of a Southern elephant seal in the Northern Hemisphere ever recorded. The unusual occurrence of a top marine predator >1,000 km from the closest marine effluent as a potential extreme case of dispersal emphasizes how marine invasions of freshwater systems have happened frequently through historical (and likely geological) time.
Comments: Definitely the weirdest paper out this year!
Van Vliet et al. 2019. A Palaeogene cetacean from Maastricht, southern Limburg (the Netherlands). Cainozoic Research.
Van Vliet et al. 2020. Eocene cetaceans from the Helmstedt region, Germany, with some remarks on Platyosphys, Basilotritus, and Pachycetus. Cainozoic Research.
Link: Not online yet.
New archaeocete remains from the Helmstedt region, Germany, are reported. The first series of bones is from the open cast mine at Alversdorf, 2 km to the northwest of Offleben, consisting of isolated vertebral centra, rib fragments and two teeth. The second series of bones, a skull fragment, an unidentifiable, triangular bone, vertebrae and rib fragments, as well as a distal tibia fragment, has been found in the open cast mine Treue, about 5 km to the northeast of Schöningen. Historically, from the same Helmstedt region, cetacean vertebrae and rib fragments have been described by Van Beneden in 1883 (and also published by Geinitz, 1883b). He regarded the remains as belonging to mysticetes from the Oligocene, for which he erected the genus Pachycetus. Here, Pachycetus robustus Van Beneden, 1883 is assigned as type species. Vertebra NsT90 is herein assigned as lectotype for that species. Kuhn (1935) ascribed these fossils to archaeocetes and added some newly found vertebrae in his description. Lienau (1984) figured additional cetacean remains from the same region. Presumably all these finds (the older as well as the new material here reported for the first time) have been derived from marine beds of the Gehlberg Formation, which is Bartonian to Priabonian in age. At least two taxa are recognised: a large one (consistent with Pachycetus Van Beneden, 1883), and a smaller one (consistent with a small ‘dorudontine’). A comparison is made between the new material and the earlier described finds, as well as with archaeocete fossils from eastern Europe (Ukraine and southwestern Russia). Some notes are added on the validity of the genus names Platyosphys Kellogg, 1936 and Basilotritus Gol’din & Zvonok, 2013, which are here referred to as Pachycetus.
Comments: The fossils are reasonably unspectacular, though some serious taxonomic changes have been made based off of them. I still haven't had a chance to read this, but when I do, I'll have to update my 'obscure controversies I' post on basilosaurid taxonomic conflicts.
Viglino et al. 2020. First toothless platanistoid from the early Miocene of Patagonia: the golden age of diversification of the Odontoceti. Journal of Mammalian Evolution.
Link: https://link.springer.com/article/10.1007/s10914-020-09505-w
Lower Miocene outcrops from Patagonia (Gaiman Formation, Burdigalian) may reveal more clues for the yet unknown aspects for this period in the evolution of odontocetes. Here, we present the first toothless platanistoid dolphin from the lower Miocene of Patagonia, Dolgopolis kinchikafiforo, gen. et sp. nov. The specimen includes an incomplete skull, with no mandibles or earbones, but sufficiently different from other named odontocetes to propose a new genus and species. Phylogenetic analyses indicate it is a platanistoid of uncertain position within the group, and that it shares some homoplastic characters with physeteroids and ziphioids. Given the absence of defined alveoli and teeth and an inferred moderately short and wide rostrum, we interpreted this new species as most likely a capture suction feeder. Based on our phylogenetic hypothesis, the optimization of feeding strategies recovered raptorial feeding as the plesiomorphic method, and convergent evolution of capture suction feeders in at least four lineages. Platanistoids recorded all feeding strategies during the late Oligocene-early Miocene, although raptorial is the predominant method. This suggests a partitioning of the ecological niches in the early phases of platanistoid evolution, as well as a high diversification of feeding methods previously underestimated for this period. Thus, ecological adaptations have a strong evolutionary pressure in odontocete communities and should be further explored.
Voss 2020. Re‑evaluation of the taxonomic and systematic status of “Halitherium” antillense Matthew, 1916 (Mammalia, Sirenia). Pal Z.
Link: https://link.springer.com/article/10.1007/s12542-020-00532-9
Halitherium antillense Matthew, 1916 was established on a left
mandibular fragment and two vertebrae from late Oligocene deposits of
Puerto Rico. This species was only provisionally referred to the genus Halitherium and its taxonomic status and systematic affinities remained doubtful. In the course of the revision of the Halitherium-species complex and the meanwhile invalid generic name “Halitherium”,
the holotype, and only known specimen, is re-investigated. A number of
morphological characters usually diagnostic in sirenians are determined.
However, the holotype material of “H.” antillense is not
informative enough and, as such, neither can be assigned to any known
species nor is it possible to define a taxon that can be clearly
distinguished from other species. Unlike other, now revised species
originally grouped under “Halitherium”, the establishment of a new taxonomic combination for “H.” antillense is not possible. As a nomenclatural consequence, the name “H.” antillense is only applicable to a single specimen, the holotype, and declared as a nomen dubium.
Zalmout et al. 2020. Marine mammals (Cetacea and Sirenia) from the middle and late Eocene of Jordan. Neues Jarbuch fur Geologie und Palaontologie.
Link: https://www.ingentaconnect.com/content/schweiz/njbgeol/2020/00000298/00000002/art00001
Marine mammals including archaeocete Cetacea and dugongid Sirenia are reported from two Eocene localities in Jordan. The first locality, Jebal eth Thuleithuwat, is Lutetian or Bartonian middle Eocene in age. Jebal eth Thuleithuwat has yielded the astragalus and other skeletal elements of a protocetid archaeocete, possible fragments of basilosaurid teeth, and the virtually complete rib of a dugongid (all gen. et sp. indet.). The second locality, Qa' Faydat ad Dahikiya is Priabonian late Eocene in age. Qa' Faydat ad Dahikiya has yielded teeth or postcranial remains of four basilosaurid archaeocetes (Stromerius nidensis, Dorudon atrox, Masracetus markgrafi, and Basilosaurus isis) and postcranial remains of a dugongid (Eotheroides sp).
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