Center for Functional Anatomy and Evolution, Johns Hopkins School of Medicine
Friday 8:30-8:45, Ballroom C
Scaling relationships among molar surface areas and their relation to dietary habits are an important focus in primate evolutionary studies. Recently, it has been proposed that root surface area (RSA), as opposed to crown surface area (CSA), directly reflects selection for heavy loading regimes. It was also suggested that RSA is susceptible to selection pressures independently of CSA. I hypothesized that: 1) within primate taxa displaying durophagous (Cercocebus, Lophocebus) or non-durophagous diets (Macaca, Papio), RSA scales isometrically with mandibular strength; 2) RSA is disproportionately larger in durophagous groups; and 3) RSA and CSA scales differentially among dietary groups. CT scans of each primate (n=47) were used to measure RSA and CSA for both Pm4 and M1. Mandibular strength (Zx, Zy) was calculated posterior to each tooth. RMA regressions were used to test scaling patterns among these properties.
RSA was significantly correlated (r>0.67; p<0.05) and scaled isometrically with mandibular strength in all genera except Lophocebus (p=0.184). Cercocebus possessed disproportionately large RSA values, as expected. Lophocebus, however, is primarily an incisal loader which may explain unexpectedly low RSA values. These results support RSA as a predictor of dietary behavior. CSA and RSA regression correlations were only significant (p<0.001) for non-durophagous groups, suggesting independent selection of RSA and CSA. This project further highlights the need to consider unique species-specific patterns when investigating adaptive influences on the masticatory complex. It also suggests that scaling relationships within dentition are complex, and future analyses should explore separate selective influences on molar crowns and roots.