Euprimates

INTRODUCTION North American fossil primates are known from the earliest Eocene to the earliest Miocene. They are very diverse and abundant in the early and early middle Eocene but decrease in diversity and abundance by the late middle Eocene and make up only a very small part of mammalian faunal samples from then until their disappearance in the early Miocene. Two suborders of fossil primates are represented in North America: Tarsiiformes, traditionally viewed as the “tarsier- or galago-like” primates of the early Cenozoic, and Adapiformes, their “lemur-like” counterparts. Tarsiiforms, represented in North America by the family Omomyidae, were a relatively small-bodied radiation and were specialized insectivores, frugivores, and faunivores. Adapiforms, represented in North America by the subfamily Notharctinae and possibly by the subfamily Cercamoniinae, were typically larger than tarsiiforms and were more generalized frugivores and folivores. Both groups were arboreal with elongate hindlimb elements, digits with nails, and opposable big toes for grasping limbs and branches of trees. Tarsiiforms had short faces and enlarged orbits and were probably nocturnal while adapiforms had longer, lower skulls with relatively smaller orbits and were probably diurnal. The decline of North American primates was the result of changing climatic conditions as relatively warm, subtropical conditions gave way to more temperate, seasonal climates beginning in the late middle Eocene. These changing climatic conditions resulted in reduction of primate habitats as closed, forested areas were replaced by more open woodlands and, later, by prairie grasslands.