Tarsils are small, primate-like mammals that belong to the order Plesiadapiformes, which are considered to be some of the earliest ancestors of modern primates. They lived during the Paleocene and Eocene epochs, approximately 65 to 34 million years ago. Tarsils are characterized by their unique dental structures and adaptations for arboreal life, including grasping hands and feet. Their fossil remains provide valuable insights into the evolutionary history of primates.