Meeting Abstract
Although studies commonly examine correlations between tooth shape and diet using taxonomically diverse mammalian samples, comparable analyses of jaw morphologies and diet across Mammalia are rare. This is surprising because mandibular shape may offer considerable insight into the diets and evolutionary histories of mammals, including fossil lineages. Jaw morphologies are expected to correlate with diet due to common functional demands on the masticatory apparatus of taxa with similar diets. I test this prediction by applying phylogenetic comparative methods to linear jaw measurements and dietary information for over 200 modern mammalian species. Results identify several jaw metrics that are significantly correlated with diet even after accounting for phylogenetic non-independence of data. The length between the jaw joint and the angular process is found to be an especially powerful predictor of diet, as it generally increases with greater herbivory. This length reflects the moment arms of the force vectors of the superficial masseter and medial pterygoid muscles, which are particularly important for transverse jaw movements and grinding of plant material. I expand on these findings by examining the evolutionary mode of jaw evolution by comparing the fit of multiple evolutionary models to the morphological data. I find strong support for the hypothesis that there are unique selective regimes associated with herbivory and carnivory. Further, mandibles of herbivorous species appear to have evolved much more rapidly than carnivores toward a trait optimum, suggesting especially strong selective pressures on these taxa. Thus, this study presents novel data concerning jaw correlates of diet across Mammalia and offers new evidence on the macroevolutionary patterns associated with mammalian diets and morphologies.
