Were plesiadapiforms likely the first primates according to modern classifications?

Plesiadapiforms are indeed considered an important group in the study of primate evolution, but modern classifications typically do not categorize them as true primates. Instead, plesiadapiforms are often viewed as a group of mammals that exhibit some primate-like traits but lack many key characteristics that define true primates, such as forward-facing eyes and postorbital closure.

The distinction is significant because while plesiadapiforms are part of the evolutionary lineage that eventually led to primates, they are not classified within the primate clade itself. This classification highlights the more derived traits that characterize true primates, which first appear in the Eocene epoch and include more advanced features related to vision, grasping abilities, and overall anatomical adaptations for an arboreal lifestyle. Thus, while plesiadapiforms contribute to our understanding of primate evolution, they are not considered the first primates according to contemporary biological classifications.