Primate Origins and Supraordinal Relationships: Morphological Evidence

Abstract

There are five major scenarios that have been advanced to account for the early events in the origination of the order Primates: a transition from terrestriality to arboreality, the adoption of a grasp‐leaping mode of locomotion, the evolution of features for visual predation, an adaptation to terminal branch feeding occurring during angiosperm diversification, or a combination involving terminal branch feeding followed by visual predation. These hypotheses are assessed using both neontological and fossil data. Of the five scenarios, the angiosperm diversification hypothesis is not contradicted by modern data and is found to be the most consistent with the fossil record. In particular, the evolution of features for manual grasping and dental processing of fruit in the earliest primates (primitive plesiadapiforms), and the subsequent development of features for better grasping and more intense frugivory in the common ancestor of Euprimates and Plesiadapoidea, is consistent with a close relationship between early primate and angiosperm evolution. All the other scenarios are less consistent with the pattern of trait acquisition through time observed in the fossil record. Consideration of non‐euprimates (e.g., scandentians and plesiadapiforms) is found to be essential to viewing primate origins as an evolutionary process rather than as an event. 1.