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You are here: Home / Library / RBINS Staff Publications 2016 / Radiation of plesiadapid mammals at the end of the Paleocene evidenced by new discoveries from the Latest Paleocene of France: one more example of bush-like evolution

Eric De Bast and Thierry Smith (2016)

Radiation of plesiadapid mammals at the end of the Paleocene evidenced by new discoveries from the Latest Paleocene of France: one more example of bush-like evolution

In: Society of Vertebrate Paleontology October 2016, ed. by Andy Farke; Amber MacKenzie; Jess Miller-Camp, vol. Astracts of papers 76th Annual Meeting, pp. 123, Society of Vertebrate Paleontology.

Plesiadapidae are usually considered to be the closest relatives to the crown-group primates, despite their disappearance at the Paleocene–Eocene Boundary (PEB) in North America, right when the first euprimates appear. In Europe, however, the family survives a few million years after the PEB, though only represented by the genus Platychoerops. Because Plesiadapis was restricted to the Paleocene and Platychoerops restricted to the Eocene, a linear evolution was implied: the genus Plesiadapis was thought to give rise to Platychoerops at the PEB due to the particular environmental conditions of that time. However, one species of Platychoerops was recently described from the late Paleocene of Berru, France, casting doubts on this hypothesis. The recently discovered locality of Petit-Pâtis (Rivecourt, Oise, France) delivered for the first time the most diagnostic tooth of Platychoerops in the Paleocene, its long and derived I1. This discovery confirms the presence of the genus Platychoerops in the Paleocene and attests a quick diversification, bush-like radiation of the family into three genera, before the PEB. The locality of Petit-Pâtis also delivered specimens referable to a new species morphologically intermediate between Plesiadapis tricuspidens and Platychoerops antiquus, with a critical I1 very similar to P. tricuspidens but closer to P. antiquus by its more molarized and proportionally larger p4; this latter derived character is shared with Platychoerops, so that the hypothesis of the North American species P. cookei being the most derived species of Plesiadapis and having given rise to Platychoerops can now be questioned, and a more geographically parsimonious hypothesis of a European origin of the European genus Platychoerops is supported. Finally, the third European genus of Plesiadapidae, Chiromyoides, is also present in Petit-Pâtis, where it is represented by a new species characterized by a smaller size than C. campanicus and the presence of relatively large accessory cuspules aside the posterocone on I1. The specimens from Petit-Pâtis also confirm the hypothesis that Platychoerops georgei from the earliest Eocene is likely a composite species based on the assemblage of a few specimens from different localities of similar estimated age, most specimens likely belonging to Plesiadapis or Platychoerops, while the holotype (a short I1) belongs either to Chiromyoides or to Plesiadapis, its preservation state making the identification difficult. Grant Information This abstract is a contribution to the project BR/121/A3/PalEurAfrica funded by the Belgian Science Policy Office.
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