The first true perissodactyls (the group that includes extant horses, rhinoceroses and tapirs) appear almost simultaneously in the fossil record from the very beginning of the Eocene (56 million years ago) in Western Europe, Asia and North America. However, they already seem to belong to distinct families. This apparent diversity raises questions about the palaeobiogeographical and phylogenetic origins of these groups, which are still the subject of much debate. Indeed, the closest relative of perissodactyls is still uncertain, although two potential sister-groups now seem to be widely accepted: perissodactyls could either be closer to certain North American Phenacodontidae (Halliday et al. 2017), or rather a sister-group of Anthracobunia from the Indian subcontinent (Rose et al. 2019). The first results of the Belspo project PerissOrigin presented here is to gain a better understanding of the first dichotomies of ancient perissodactyls and their palaeobiogeographical origins. Thanks to a revision of the oldest known fossil perissodactyls, a new phylogeny has been carried out. This new phylogeny enables to define some synapomorphies of the major groups of perissodactyls and to propose a palaeobiogeographical scenario. It also shows that the earliest known perissodactyls were much more cosmopolitan than previously thought, and that some genera that were thought to be endemic from Europe were actually also found in North America and Asia. Finally, we discuss the unresolved problems in the phylogeny of Perissodactyla, notably the uncertain position of Palaeotheriidae (a group endemic to Europe) and the absence of postcranial characters in our analysis.
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RBINS Staff Publications 2024
The Crocodylia include all modern crocodiles, alligators, caimans and gharials, and their extinct relatives. They are an ancient lineage that originated around 70 million years ago. Recently, the field of crocodylian paleontology has experienced a rise in attention from researchers, however, much is still unknown about the early evolution of this group. Our research describes newly discovered fossil material comprised of a small crocodylian skull and associated partial lower jaw of early Paleocene age. It was discovered during a Belgian-Chinese expedition in Qianshan Basin, Anhui Province, China, as part of a bilateral cooperation project between the Royal Belgian Institute of Natural Sciences and the Institute of Botany of the Chinese Academy of Sciences. In the present study, the fossil material is formally described for the first time. Micro-CT scans are made to visualize internal anatomical structures, as well as characters hidden by the sediment. A comprehensive morphological study is executed, revealing that the specimen is a juvenile. It likely constitutes a new species and genus, as it differs from other crocodyloids by several autapomorphies. A phylogenetic analysis based on morphological characteristics reveal that this specimen is the most basal taxon among Crocodyloidea, a group that comprises all species more closely related to modern crocodiles than to modern alligators, caimans, or gharials. Although it is not the oldest crocodyloid ever reported, it is the earliest crocodyloid in Asia. Moreover, its basal phylogenetic position implies that it is part of an ancient ghost lineage of crocodyloids that had already been around in Asia for a longer time. The presence of crocodyloid remains in the Late Cretaceous of North America and the late Paleocene of Europe suggests that crocodyloids may have migrated there from Asia early on in their evolutionary history.
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RBINS Staff Publications 2021
