Plesiadapiformes ("Adapid-like" or "near Adapiformes") is a group of Primates, a sister of the Dermoptera. While none of the groups normally directly assigned to this group survived, the group appears actually not to be literally extinct (in the sense of having no living descendants) as the remaining primates (the crown primates or "Euprimates") appear to be derived Plesiadapiformes, as a sister of e.g. the Carpolestidae. The term Plesiadapiformes may still be used for all primates which are not crown primates, but this usage is paraphyletic. When the crown primates are cladistically granted, it becomes an obsolete junior synonym to primates. Purgatorius is believed to be a basal Plesiadapiformes. Plesiadapiformes first appear in the fossil record between 65 and 55 million years ago, although many were extinct by the beginning of the Eocene. They may have been the first mammals to have finger nails in place of claws. In 1990, K.C. Beard attempted to link the Plesiadapiformes with the order Dermoptera. They proposed that paromomyid Phenacolemur had digital proportions of the fossil indicated gliding habits similar to that of colugos. In the following simplified cladogram, the crown primates are found to be highly derived Plesiadapiformes, possibly as sister of the Plesiadapoidea. The crown primates are cladistically granted here into the Plesiadapiformes, and the 'plesiadapiformes' become a junior synonym of the primates. With this tree, the plesiadapiformes are not literally extinct (in the sense of having no surviving descendants). The crown primates are also called "Euprimates" in this context. Alternatively, in 2018, the plesiadapiform were proposed to be more related to Dermoptera, or roughly corresponding to Primatomorpha with both Dermoptera and the primates emerging within this group. Also in a 2020 paper, the primates and Dermoptera were jointly considered sister to the plesiadapiform Purgatoriidae, resulting in the following phylogenetic tree. Traditionally, they were regarded as a separate extinct order of Primatomorpha, but it now appears that groups such as the extant primates and/or the Dermoptera have emerged in the group. One possible classification table of plesiadapiform families is listed below. PLESIADAPIFORMES Family Micromomyidae Superfamily Paromomyoidea Family Paromomyidae Family Picromomyidae Family Palaechthonidae Family Microsyopidae Superfamily Plesiadapoidea Family Carpolestidae Family Chronolestidae Family Picrodontidae Family Plesiadapidae Family Saxonellidae References External links Mikko's Phylogeny Archive Mammal orders Paleocene first appearances Eocene extinctions Paraphyletic groups