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First virtual endocasts of two Paleocene arctocyonids: a glimpse into the behavior of early placental mammals after the end-Cretaceous extinction
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Placentals are by far the most diverse group of mammals today, with 6,111 species. They occupy a plethora of ecological niches worldwide and display a broad range of body masses. The vacant niches left by non-avian dinosaurs and other vertebrates after the end-Cretaceous mass extinction provided a crucial opportunity for placentals to diversify; however, intrinsic factors also may have played a role. The general neurosensory organization exhibited by extant mammals has been maintained since the early Mesozoic. Much later, early members of extant placental groups from the Eocene and Oligocene including rodents, primates and artiodactyls—display neurosensory innovations such as a proportionally larger neocortex and higher encephalization quotient compared to their Mesozoic ancestors. However, between these two well-known intervals of mammalian neurosensory evolution, there is a gap: few studies have focused on the brains of the oldest placentals living during the early Paleogene, in the Paleocene. We focus on the ‘Arctocyonidae’, a likely polyphyletic group of ‘condylarths’, including species potentially implicated in the origins of some extant orders. ‘Arctocyonids’ were among the first placentals to diversify after the end-Cretaceous extinction. They have been reconstructed as small-tomedium sized, mainly omnivorous and terrestrial. We obtained cranial and bony labyrinth endocasts for Chriacus baldwini and C. pelvidens from the lower Paleocene of the San Juan Basin, New Mexico, and Arctocyon primaevus from the upper Paleocene of the Paris Basin, France, via high resolution computed tomography. Both share plesiomorphic brain features with previously described early Paleocene mammals. They have small lissencephalic brains with an EQ range of 0.12-0.43 and 0.16-0.31, respectively. The olfactory bulbs and the paraflocculi represent 6% and less than 1% of the total endocranial volume, respectively and the neocortical height ratio represents ~25% of the total endocranial height. Based on cochlear measurements, both taxa had hearing capabilities similar to those of extant wild boars. Agility scores between 2 and 3 were obtained for both taxa, similar to the modern American badger and crab-eating raccoon, suggesting that C. pelvidens and A. primaevus were ambulatory. These results support growing evidence that early placentals had lower EQs and less expanded neocortices compared to Eocene and later taxa, potentially indicating that high intelligence was not key to the placental radiation after the End-Cretaceous extinction. Grant Information: Marie Sklodowska-Curie Actions: Individual Fellowship, European Research Council Starting Grant, National Science Foundation, and Belgian Science Policy Office.
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RBINS Staff Publications 2019
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Paleocene and Eocene bird assemblage from the Southern North Sea Basin
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Numerous bird bones from the Paleocene and early Eocene of the Belgian and Paris basins have been collected by amateur paleontologists. Four bones from the early-middle Selandian of Maret, Belgium are among the earliest Cenozoic avian remains from Europe and include the oldest temporally well constrained records of the Gastornithidae, as well as tentative records of the paleognathous Lithornithidae and the Ralloidea. Another assemblage from the middle Thanetian of Templeuve, France contains multiple bones of the Lithornithidae as well as a record of the Pelagornithidae. Specimens from the latest Thanetian of Rivecourt-Petit Pâtis, France are tentatively assigned to the Ralloidea and Leptosomiformes. An assemblage of 54 bones from the middle Ypresian of Egem, Belgium represents at least 20 species in more than 11 higher-level taxa. Well-identifiable specimens are assigned to the Odontopterygiformes, Galliformes, Messelornithidae, Apodiformes, Halcyornithidae, Leptosomiformes, and Coraciiformes. Further specimens are tentatively referred to the phaethontiform Prophaethontidae and to the Accipitridae, Masillaraptoridae, and Alcediniformes. These three-dimensionally preserved fossils provide new data on the osteology of taxa that are otherwise mainly known from compression fossils with crushed bones. They also further knowledge of the composition of early Paleogene avifaunas of the North Sea Basin. Paleocene avifaunas of Europe and North America appear to have had different compositions and only a few taxa, such as the paleognathous Lithornithidae, are known from both continents. This suggests that the very similar early Eocene avifaunas of Europe and North America are the result of early Cenozoic dispersal events. The well-represented small galliform species from Egem most closely resembles Argillipes aurorum, an ignored galliform species from the London Clay. The tentatively identified fossils of Accipitridae and Alcediniformes would represent the earliest fossil records of these clades. The birds from Egem include few seabirds (Odontopterygiformes, cf. Prophaethontidae) and is dominated by terrestrial species (Galliformes, Messelornithidae). Arboreal birds (Halcyornithidae, Leptosomiformes, cf. Alcediniformes, Coraciiformes) are less abundant and aerial insectivores (Apodiformes) very scarce, which either indicates a taphonomic bias in the composition of the avifauna or particular paleoenvironmental characteristics of the nearshore habitats in that area of the southern North Sea Basin. Grant Information: Funded by Belgian Science Policy Office (project BR/121/A3/PalEurAfrica).
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RBINS Staff Publications 2019
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Large-scale and small-scale population genetic structure of the medically important gastropod species Bulinus truncatus (Gastropoda, Heterobranchia)
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RBINS Staff Publications 2022
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Reevaluating the timing of Neanderthal disappearance in Northwest Europe
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Understanding when Neanderthals disappeared is a hotly debated topic. When radiocarbon dating placed the Spy Neanderthals amongst the latest surviving in Northwest Europe, questions were raised regarding the reliability of the dates. Using a procedure more efficient in removing contamination and ancient genomic analysis, we show that previous dates produced on Neanderthal specimens from Spy are too young by up to 10,000 y. Our direct radiocarbon dates on the Neanderthals from Spy and those from Engis and Fonds-de-Forêt show a reduction of the uncertainty for the time window corresponding to Neanderthal disappearance in Northwest Europe. This population disappeared at 44,200 to 40,600 cal B.P. (at 95.4% probability). This is also earlier than previous suggestions based on dates on bulk collagen.Elucidating when Neanderthal populations disappeared from Eurasia is a key question in paleoanthropology, and Belgium is one of the key regions for studying the Middle to Upper Paleolithic transition. Previous radiocarbon dating placed the Spy Neanderthals among the latest surviving Neanderthals in Northwest Europe with reported dates as young as 23,880 ± 240 B.P. (OxA-8912). Questions were raised, however, regarding the reliability of these dates. Soil contamination and carbon-based conservation products are known to cause problems during the radiocarbon dating of bulk collagen samples. Employing a compound-specific approach that is today the most efficient in removing contamination and ancient genomic analysis, we demonstrate here that previous dates produced on Neanderthal specimens from Spy were inaccurately young by up to 10,000 y due to the presence of unremoved contamination. Our compound-specific radiocarbon dates on the Neanderthals from Spy and those from Engis and Fonds-de-Forêt demonstrate that they disappeared from Northwest Europe at 44,200 to 40,600 cal B.P. (at 95.4% probability), much earlier than previously suggested. Our data contribute significantly to refining models for Neanderthal disappearance in Europe and, more broadly, show that chronometric models regarding the appearance or disappearance of animal or hominin groups should be based only on radiocarbon dates obtained using robust pretreatment methods.All the radiocarbon data generated at the ORAU are archived internally and are also available on the laboratory’s website, along with a link to the paper. The mitochondrial genome from Fonds-de-Forêt is deposited in GenBank with the accession number PRJEB39136. All other study data are included in the article and/or SI Appendix.
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RBINS Staff Publications 2021
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Chapter 12 - New Specimens of Frugivastodon (Mammalia: Apatotheria) from the Early Eocene of India Confirm Its Apatemyid Status and Elucidate Dispersal of Apatemyidae
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We here describe 18 new specimens of the sole apatemyid mammal known outside North America and Europe: Frugivastodon cristatus from the early Eocene Cambay Shale Formation of Vastan Lignite Mine, Gujarat, India. This mammal was previously represented by a single isolated lower molar, which hindered the establishment of its relationships among Apatemyidae. The new fossils show that the Indian apatemyid is unique and represents a new morphotype among this family. It is notably characterized by mesiodistally elongated lower molars with a reduced m3, a small hypocone on the upper molars, and a transversely wider M1 than in other apatemyids. The new data supports the inclusion of the enigmatic Uintan Aethomylos within Apatemyidae. The Indian Frugivastodon and the North American Aethomylos might represent a distinct clade of Apatemyidae that originated around the Paleocene-Eocene boundary. A paleobiogeographic analysis suggests that Frugivastodon dispersed from Europe into India during the early Ypresian. We also review the dispersal events that characterized the history of Apatemyidae.
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RBINS Staff Publications 2020
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Recent advances in heteromorph ammonoid palaeobiology
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RBINS Staff Publications 2021
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A fossil heron from the early Oligocene of Belgium : the earliest temporary well-constrained record of the Ardeidae
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We describe the earliest temporally well-constrained fossil that can be assigned to the Ardeidae (herons), from the lowermost Oligocene (32.0–33.0 million years ago) of Belgium. The specimen, a partial tarsometatarsus, belongs to a small species and is described as Proardea? deschutteri n. sp. It exhibits the characteristic tarsometatarsus morphology found in extant heron species, but a confident assignment to one of the ardeid subclades is not possible and even the assignment of the new fossil species to the crown group (the clade including the extant species) cannot be established. The fossil indicates a divergence of herons from their sister taxon by at least the earliest Oligocene, and current paleontological data suggest that herons arrived in Europe shortly after a major faunal turnover at the Eocene/Oligocene boundary. We consider that dispersal is the likely reason for the sudden appearance of herons in the earliest Oligocene of Europe but it is uncertain from where exactly this took place, with Asia and Africa being among the candidate areas.
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RBINS Staff Publications 2018
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A peculiar fish jaw with molariform teeth from the early Eocene of Tadkeshwar Mine, India highlights diversity and evolution of early gymnodont tetraodontiforms
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Excavations during 2015 at a channel deposit in the early Eocene Cambay Shale Formation of the Tadkeshwar open cast lignite mine near Vastan in Gujarat Province, western India, have yielded terrestrial mammals, lizards, snakes, frogs, and birds as well as a few marine/brackish-water animals, predominantly teeth of the shark Physogaleus and Myliobatis rays. Among these is a jaw of an unusual teleost. This lower jaw of a gymnodont has fused dentaries, lacks a beak, and shows a remarkable series of teeth that are unique among all known fossil and living Tetraodontiformes. The teeth are molariform with raised “spokes” radiating inward from the emarginated peripheral edge of the crown. Tooth development is intraosseous, with new teeth developing in spongy bone before they erupt and attach to the dentary by pedicels. Although many of the 110 tooth loci in the fossil specimen have lost their teeth, in life the teeth would have grown to fit tightly together to form a broad and continuous crushing surface. The estimated age of the early Eocene Cambay Shale vertebrate fauna is ca. 54.5 Ma, making the jaw the second oldest confirmed gymnodont fossil. Comparisons to extant taxa of gymnodonts with fused dentaries (e.g., Diodon, Chilomycterus, and Mola) offer few clues about evolutionary relationships of the new fossil. Although the fused dentaries suggest affinities to diodontids and molids among living tetraodontiforms, it remains challenging to interpret phylogenetic relationships of the new Indian gymnodont because no living or fossil tetraodontoid has similar tooth morphology. We describe it as a new genus and species, and place it in its own new family of Gymnodontes. Grant Information: National Geographic Society, Leakey Foundation, Belgian Science Policy Office, Tontogany Creek Fund, National Science Foundation, Wadia Institute of Himalayan Geology.
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RBINS Staff Publications 2017
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An enigmatic ungulate from the early Eocene of India
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The early Eocene Cambay Shale Formation in Gujarat State, India has produced a rich mammalian fauna, including the earliest artiodactyls, perissodactyls, primates, hyaenodonts, rodents, lagomorphs, chiropterans, and tillodonts from the Indian Subcontinent. While some of these groups show endemism at the generic or familial level, all belong to clades that are widely distributed across Laurasian continents, and some show particularly close similarities to contemporary taxa from other continents, particularly Europe. We report here a distinctive new taxon, represented by a mandible with p3-m3 and a second mandibular fragment with m3. The morphology of the new taxon is broadly comparable to diverse early ungulates from around the world but shows a unique suite of features including a strongly fused mandibular symphysis, enlarged anterior tooth alveolus, simple premolars lacking paraconids and with only a rudimentary metaconid on p4, progressive size increase of the molars distally, molar exodaenodonty/unilateral hypsodonty, molar paraconids absent, hypoconulids absent on m1-2, incipient development of selenodont buccal cusps and an incipient entolophid formed by a transverse entoconid, well-developed, and prominent m3 hypoconulid. One particularly distinctive feature is the presence of large, cuspate ectostylids on molar hypoflexids. While there are similarities to a variety of taxa, most notably periptychids, louisinids, early African “ungulates” (Abdounodus, Ocepeia), and even early anthracotheres, none of these is detailed enough to indicate a close relationship, and all appear to be better interpreted as convergence. Our present understanding suggests that these fossils represent a new family of “condylarth”-grade ungulates perhaps endemic to India. Although their overall adaptations are very different, there are some intriguing similarities to another group of enigmatic Eocene mammals from the Indian Subcontinent, Quettacyonidae. While more material is needed to test this possible relationship, quettacyonids and the new taxon may represent remnants of the eutherian fauna present in India prior to its first faunal exchange with the northern continents, and the new taxon likely has a lengthy, undocumented history in the Indian Paleocene. Grant Information: Fieldwork and research supported by Leakey Foundation, National Geographic Society, Wadia Institute of Himalayan Geology, and Belgian Science Policy Office.
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RBINS Staff Publications 2017
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Taxonomic Revision of the Genus Trictenotoma Gray, 1832 (Coleoptera: Trictenotomidae). Part 3 – Species from the Philippine Archipelago, with Description of a New Species
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RBINS Staff Publications 2021
