Carpolestes

Abstract: SPECIES in or near the ancestry of living primates first appear in the late Cretaceous and early Palaeocene of North America. Subsequent adaptive radiation of the Purgatorius-like ancestral stock produced the plesiadapoid families (Plesiadapidae, Carpolestidae, Paromomyidae) of the middle and late Palaeocene. Specialised members of all three families survived into the early Eocene, the paromomyid genus Phenacolemur persisting into the late Eocene. Most of the plesiadapoid species are known only from incomplete dentitions. In 1948, a crushed but nearly complete skull of a paromomyid was recovered from strata of middle Palaeocene age in the Kutz Canyon area of the San Juan Basin, New Mexico. The specimen has been described by Wilson and Szalay1, who assign it to a new species (P. nacimienti) of the genus Palaechthon, known also from the mid-Palaeocene of Montana and Wyoming. The loss of the upper and lower first premolars excludes P. nacimienti from the ancestry of some of the Eocene prosimian lineages. Nevertheless, its persistently primitive molar morphology suggests that it may more closely resemble the last common ancestor of the plesiadapoids and the Eocene primates of modern aspect than do other plesiadapoids for which cranial remains are known. Skulls or partial skulls are known for dentally more specialised genera of each plesiadapoid family: Plesiadapis (Plesiadapidae), Carpolestes (Carpolestidae), and Phenacolemur (Paromomyidae).) We present here a reconstruction of the skull of P. nacimienti, together with some preliminary functional interpretations of its cranial and dental anatomy.

Abstract: 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 Ca...