46 - Wear-mediated Changes in Molar Sharpness of Cercopithecid Primates

Poster Board Number: 46
There are separate poster presentation times for odd and even posters.
Odd poster #s – first hour
Even poster #s – second hour

Abstract Body : The primary function of the mammalian postcanine dentition is to break down food particles to facilitate digestion. Herbivores experience significant alteration of the occlusal surface over the course of a lifetime as dental tissues are lost through wear. Primates are relatively long-lived mammals with low-crowned postcanine teeth, lacking many of the dental morphological features that combat loss of functionality with wear in other herbivorous clades (e.g., hypsodont crowns, complex grinding surfaces of interposed tissues). Despite these limitations, studies of wear-mediated changes in primate molar morphology have suggested that the molars of some folivorous and gramnivorous taxa retain functionally-relevant cutting surfaces through the exposure of compensatory crests along exposed dentine pools until relatively late stages of wear.

Based on research from platyrrhine primates (New World monkeys), the ‘dental sculpting hypothesis’ proposes that the molars of some folivorous primates undergo adaptive wear-based changes that increase occlusal sharpness, while non-folivores do not exhibit these increases. Cercopithecids (Old World monkeys) are a speciose primate clade that exhibit considerable dietary diversity but share molars with a conserved bilophodont cusp configuration, making them an ideal group to test this hypothesis. Here, we apply dental topographic methods to quantify sharpness of lower second molars using convex dirichlet normal energy (DNE), a metric of the total curvature of convex features on the occlusal surface. We apply this metric to cross-sectional wear series of 19 cercopithecid primate species (n=393) to explore how occlusal sharpness changes with progressive wear in folivorous, frugivorous, and hard-object feeding taxa.

Results from regression analyses of convex DNE against percent dentine exposure demonstrate that increases in sharpness with progressive wear are not found among cercopithecids. The molars of cercopithecids in this sample either maintain or decrease in convex DNE with progressive wear, but these directional changes do not map onto broad dietary categories nor percent foliage in the diet. Comparisons between dietary groups show that the molars of folivores have significantly higher convex DNE values than frugivores and hard-object feeders at all but the heaviest wear stages. While wear-mediated patterns of change in convex DNE do not track dietary categories in extant cercopithecids, this metric is still a useful tool when comparably worn molars are compared for inferring diet from extinct taxa.