A new species of Carpolestes (Mammalia, Plesiadapoidea) from the late Paleocene of southern Wyoming: assessing changes in size and shape during the evolution of a key anatomical feature
A new and phylogenetically basal species of Carpolestes, the youngest and most derived genus of the plesiadapoid family Carpolestidae in North America, is described from a late Tiffanian (Ti-5) site in Sweetwater County, Wyoming, USA. Carpolestids differ from closely related plesiadapoid clades in having an enlarged, multicuspidate, blade-like P4 that is partly convergent on that of multituberculates and other mammals showing plagiaulacoid dental adaptations. With some notable exceptions, the evolutionary history of North American carpolestids is characterized by the progressive development of larger and more elaborate P4 blades through time. In particular, species of the monophyletic genus Carpolestes differ from species assigned to the earlier and apparently paraphyletic genus Carpodaptes in terms of both the size and shape of their P4. A geometric morphometric analysis reveals that, with respect to P4 shape, the closest approximation to the highly derived morphology of Carpolestes is made by Carpodaptes hobackensis, which is one of the smallest known species of Carpodaptes. In contrast, the largest known species of Carpodaptes, Carpodaptes jepseni, has a P4 that falls within the metric range of variation for species of Carpolestes, yet Carpodaptes jepseni shows a uniquely derived P4 shape that seems to exclude it from any special phylogenetic relationship with Carpolestes. A phylogenetic analysis based on dental characters reconstructs Carpodaptes hobackensis as the sister group of the Carpolestes clade. Shape seems to have been a more important factor than size during the final transformation of the blade-like P4 of North American carpolestids.
http://zoobank.org/urn:lsid:zoobank.org:pub:212F9ECC-DA9A-44F8-BE7E-43F3EBAD636A
