Department of Anthropology, Iowa State University
Thursday Morning, Ballroom C
The evolution of Eocene euprimates in North America produced a diverse array of species that filled many ecological niches, however, due to poor preservation, little is known about their life history. Based on a few existing complete skulls, adapids have been suggested to be sexually size dimorphic, while omomyids are said to be monomorphic like the closely related tarsiers. The degree of sexual dimorphism in other early primates, like microsyopids, is unknown. The pattern of sexual dimorphism across primates may be indicative of both social organization as well as phylogenetic relatedness. The goal of this study was to measure the degree of sexual size dimorphism across a wider taxonomic range of Eocene euprimates than has previously been reported. I measured a single tooth type of representative species of adapid (Notharctus nunienus, N. venticolus, Cantius ralstoni), omomyid (Omomys carteri) and microsyopid (Microsyops elegans), then used cluster analysis to determine if each sample could be grouped into two distinct size-based clusters with significantly different means. I mapped the proportion of sexual size dimorphism onto a phylogenetic tree and used independent contrasts to test for the effect of phylogeny. The results confirm that some notharctid adapids were dentally sexually size dimorphic, while omomyids and microsyopids are monomorphic with respect to dental size. These results have implications for the pattern of evolution of sexual dimorphism in primates – sexual size dimorphism appears to be a plastic trait that evolves repeatedly in distantly related lineages, and likely does not carry a strong phylogenetic signal.
This project was funded the Department of Anthropology at Iowa State University.