Doctoral Dissertation Research: Unraveling primate supraordinal relationships: Insights from plesiadapiform cranial morphology

Cuny Brooklyn College, Brooklyn NY

Investigators

Abstract

Central to unraveling the origin of primates - the mammalian group to which humans belong - are the fossils of plesiadapiforms, extinct members of a group (Euarchonta) consisting of primates and closely related mammals. While some plesiadapiforms have long been suggested to share characteristics with some contemporary primates, additional analyses of the plesiadapiforms using newer, state-of-the-art methodologies can further advance our understanding of primate origins. This doctoral dissertation project uses methods such as high-resolution X-ray micro computed tomography (μCT) to analyze and compare the cranial anatomy of plesiadapiforms to that of extant primates and other placental mammals. Detailed cranial comparisons are generated that can add to the evaluation of evolutionary relationships among plesiadapiforms, extant primates, and other euarchontan mammals, in the context of a new evolutionary tree. This project also provides numerous opportunities for outreach through mentorship, public science engagement events, and data sharing. Insights from this project can be incorporated into programs that facilitate participation from groups underrepresented in STEM. The investigators also train undergraduate and master’s students in aspects of CT scan data processing, 3D printing, computer coding, and basic fossil preparation. The investigators plan to make all data generated from this project, such as CT scan data and data matrices, freely available on public online repositories to allow for repeatability and to enable future studies on primate evolution. Plesiadapiform crania have traditionally played an important role in hypotheses about primate origins but remain poorly understood because they are unknown for a large majority of plesiadapiform species and because many of the known cranial specimens have not been analyzed using modern CT techniques. This study uses modern high-resolution CT technology to document new plesiadapiform cranial anatomy, reevaluate previously published cranial descriptions, and make thorough cranial comparisons among primates and other placental mammals. These data are incorporated into a new character-taxon matrix that is analyzed using both parsimony and Bayesian phylogenetic methods to assess evolutionary relationships. Results from these analyses can allow investigators to assess (i) which, if any, cranial features are uniquely shared among plesiadapiforms and primates of modern aspect, (ii) interrelationships among plesiadapiform families, and (iii) hypotheses of plesiadapiform evolutionary relationships within Euarchonta. Ultimately, these new data can provide clarity on previously proposed shared cranial features among plesiadapiforms and primates of modern aspect and will promote a better understanding of the divergence of primates from other mammals and the first steps in primate evolutionary history. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.