Incisor cross-sectional area at the cementoenamel junction correlates with an increased reliance on frugivory in anthropoid primates

Abstract

Diet is one of a limited set of key ecological parameters defining primate species. A detailed understanding of dental functional correlates with primate diet is a key component for accurate dietary inference in fossil primates. Although considerable effort has been devoted to understanding post-canine dental function, incisor function remains poorly understood. Prior analyses have demonstrated that anthropoid incisor mesiodistal (MD) and cervico-incisal (CI) crown curvature correlates with an increased reliance on frugivory and that greater incisor crown curvature functions to increase total crown area and, by extension, crown resistance to normal bending stresses (e.g., compressive and tensile forces). The present study investigates the correlation between incisor basal cross-sectional area at the cementoenamel junction (CA^cej) and the degree to which taxa rely on frugivory to better understand how non-normal forces (e.g., shear) may influence incisor morphology. Results demonstrate that, like resistance to bending stress, resistance to shear stress (as represented by the CA^cej), is positively correlated with an increased reliance on frugivory such that more frugivorous anthropoids have larger CA^cej relative to body mass and therefore greater resistance to shear stress. Likewise, hard-object frugivores have increased shear resistance relative to soft-object frugivores. A more detailed working understanding of the forces acting on primate incisors, and how these crowns resist those forces, will contribute to improving our understanding of how diet influences incisor morphology and the accuracy of dietary inference in fossil anthropoids.