Doctoral Dissertation Improvement: Comparative and functional morphology of primate ungulae and distal phalanges

Suny At Stony Brook, Stony Brook NY

Investigators

Abstract

Flattened nails are a defining feature of humans and other primates; they are one of the few traits that unite this Order. Furthermore, the presence or absence of specialized nails distinguishes the three major extant primate groups: strepsirrhines (lemurs, lorises, and galagos) possess a grooming claw on the second toe of each foot, tarsiers have one on both the second and third toes, and most anthropoids have none. This project, conducted by doctoral student Stephanie A. Maiolino under the guidance of Dr. William L. Jungers (Stony Brook University), intends to assess the origin, evolution, and diversity of primate nails and grooming claws within a broadly comparative mammalian context. A large database of high resolution digital photographs and ìCT scans of nails and distal phalanges will be collected. ìCT scanning is employed as a non-destructive method of sampling bones embedded within preserved mammalian skins and cadavers. Quantitative data will be analyzed to interpret the functional and phylogenetic significance of extant distal phalanx and nail shape, and to interpret the form of the distal phalanges of the earliest fossil primates. Ancestral state reconstructions will be used to assess the homologies and polarities of grooming claw form in different primate groups. This research will supply information that is integral to the understanding of broad questions of primate origins and diversification. It will provide data on the evolutionary transition from a claw-bearing ancestor into a nail-bearing primate, a primary component of theories of primate origins. Additionally, an understanding of the polarity of grooming claws among primate clades will be gained; this is critical to systematic analyses of controversial fossils. Finally, this study will help elucidate the functional and phylogenetic implications of an often cited, but poorly understood primate trait. This project promotes the education of a female graduate student and provides opportunities for collaborations with fellow students. It also includes the training and education of high school and undergraduate students in 3D and 2D imaging. MicroCT scans collected for this project will be shared using a free online repository, thus allowing data that were previously unavailable to be broadly accessed. Finally, results will be disseminated in peer reviewed journals, professional meetings, and public talks.