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
