Plesiadapiform in the context of "Purgatorius"

This is a list of fossil primates—extinct primates for which a fossil record exists. Primates are generally thought to have evolved from a small, unspecialized mammal, which probably fed on insects and fruits. However, the precise source of the primates remains controversial and even their arboreal origin has recently been questioned. As it has been suggested, many other mammal orders are arboreal too, but they have not developed the same characteristics as primates. Nowadays, some well known genera, such as Purgatorius and Plesiadapis, thought to be the most ancient primates for a long time, are not usually considered as such by recent authors, who tend to include them in the new order Plesiadapiformes, within superorder Euarchontoglires. Some, to avoid confusions, employ the unranked term Euprimates, which excludes Plesiadapiformes. That denomination is not used here.

There is an academic debate on the time the first primates appeared. One of the earliest probable primate fossils is the problematic Altiatlasius koulchii, perhaps an Omomyid, but perhaps a non-Primate Plesiadapiform, which lived in Morocco, during the Paleocene, around 60 Ma. However, other studies, including molecular clock studies, have estimated the origin of the primate branch to have been in the mid-Cretaceous period, around 85 Ma, that is to say, in the time previous to the extinction of dinosaurs and the successful mammal radiation. Nevertheless, there seems to be a consensus about the monophyletic origin of the order, although the evidence is not clear.