Plesiadapiformes

Plesiadapiformes is an extinct group of mammals that lived during the Paleocene and Eocene periods, approximately 55–35 million years ago. These animals had characteristics of both primates and rodents and are sometimes called "primitive primates." They were mouse-sized creatures with large eyes, long tails, and long claws. Plesiadapiformes are important to understanding the evolutionary development of primates, as they show some of the adaptations that allowed primates to evolve from their ancestors. This group of animals was also useful in determining the paleoenvironment and the relationships between different extinct animals.