This project seeks to determine the ancestral skeletal structure and ecological niche of a family of archaic primates, the Plesiadapidae, which lived primarily during the Paleocene epoch, 65-55 million years ago, in North America and Europe.
Modern primates, including apes and humans, New and Old World monkeys, lemurs, lorises, and tarsiers, are recognized by a unique suite of anatomical features of the skeleton. The common ancestor of modern primates also had these features, as well as certain other features retained by only some primate groups today. Several hypotheses exist regarding the adaptive significance of these "ancestral primate features", which can be most directly tested using the fossil record. This study of the Plesiadapidae, a close fossil relative of the common ancestor of modern primates, can help illuminate the pattern of acquisition of primate features through the history of change in a lineage leading from non-primates to modern primates. It thereby tests adaptive hypotheses that predict simultaneous appearance (in the same fossil) of certain sets of features.
Specifically, the PI is gathering data that ultimately bears on the recent controversial hypothesis that specializations for grasping with an opposable big toe, sporting a nail, instead of a claw, preceded acquisition of certain features of the visual system (forward facing orbits) in the ecological history of primates. Determination of characteristics of the ancestor of Plesiadapidae requires a revision of species level taxonomy, a revision of inter-relationships among members of the group, and a comprehensive quantitative study of the ecological niche of these animals, including aspects of dietary preference and locomotor repertoires.
Pilot data suggest that the taxonomy and pattern of relationships among members of the Plesiadapidae are poorly understood, but that new data and analyses will clarify the genealogy. Further, new skeletal material suggests that early members had a better-developed grasping foot than later members, which went on to develop numerous, currently undocumented, ecological specializations.
Broader impacts of this project include the potential to clarify the ecological context in which physical features characterizing modern primates first appeared. Such information is of interest to physical and behavioral anthropologists, neontologists, neurobiologists, the broader scientific community, and even the public in general because it provides an explanation of the mechanisms by which primates and humans acquired their distinctive features. These explanations affect the types of research questions that are pursued in related fields. Furthermore, this project will create a large data archive in the form of (1) high resolution CT-scan images of skulls, and (2) laser scan images and digital photographs of teeth and postcranial bones that can be used in other quantitative studies in which morphology of plesiadapid primates is relevant. The grant will also provide training for a graduate student.
