Plesiadapid mammals from the latest Paleocene of France offer new insights on the evolution of Plesiadapis during the Paleocene-Eocene transition

Plesiadapidae are among the most successful mammal families of the Paleocene, but in North America they disappear abruptly around the Paleocene-Eocene boundary. In contrast, in Europe, they survive a few million years into the Eocene, although only as the genus Platychoerops. The latest Paleocene deposits of Petit-P^atis (Paris Basin, France) have produced three new plesiadapid species, one of each genus known in Europe: Plesiadapis ploegi, sp. nov., Platychoerops boyeri, sp. nov., and Chiromyoides mauberti, sp. nov. Each of these new species is represented by the very characteristic upper incisor, thus ascertaining their concomitant presence and in particular the spatial and temporal coexistence of Plesiadapis and Platychoerops. Plesiadapis ploegi, sp. nov., is morphologically intermediate between Plesiadapis tricuspidens and Platychoerops russelli, with a tricuspid I1 typical of Plesiadapis and a semimolariform p4 closer to Platychoerops. Its relatively high morphological variability is illustrated. Platychoerops boyeri, sp. nov., has the simple derived I1 of all Platychoerops and a p4 slightly more molariform than that of Ples. ploegi. Chiromyoides mauberti, sp. nov., is closest to Chiromyoides campanicus, but it is smaller and has a particular I1 with multiple posterocones. The systematic position of ‘Platychoerops’ georgei is discussed; this taxon is considered a chimera, and its type I1 belongs to either Chiromyoides or Plesiadapis. Cladistic analysis highlights the paraphyly or polyphyly of all genera of Plesiadapidae. Finally, there is some indication of morphological convergences between European and North American plesiadapids, which may be the result of similar environmental changes on both continents just before the Paleocene-Eocene boundary.

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Paleontology