Foraging Strategies, Adaptive Radiation, and Evolutionary Morphology of the Callitrichidae (Mammalia, Primates) - Craniometric Evidence. (Paperback)

Marmosets, the smallest anthropoid primates, are unique among the Haplorhini due to the use of their anterior dentition to elicit exudate flows, a behavior known as tree-gouging. Tree-gouging is a stressful, craniofacially-dominated feeding behavior, but craniofacial adaptations to this behavior, if any, are poorly understood. This thesis reports findings from univariate and multivariate analyses of the callitrichid facial skeleton, suggests anatomical adaptations for tree-gouging among marmosets, and discusses the implications of these analyses to current models of platyrrhine evolution. Analyses suggest that marmosets and non-gouging callitrichids differ in terms of craniofacial anatomy. Multivariate pattern analyses suggest that gougers have relatively long, wide skulls, narrow palates, small mandibles, long and narrow mandibular condyle articular surfaces, short coronoid processes, and low mandibular condyles. However, univariate analyses suggest that few of these patterned differences reach the level of statistical significance. Nevertheless, univariate analyses show that gougers do have significantly longer anterior basicrania/palates, shorter ascending rami at the coronoid process, and narrower anterior palates. Qualitative analyses of callitrichid crania suggest that gougers have expanded sphenoidal regions due to posterior displacement of the foramen magnum, possibly accounting for the increased basicranial length. These characters all relate to increasing jaw gape, increasing the efficiency of force utilization, and/or transmitting force, not producing large bite-forces. These results show that the acquisition of a novel foraging strategy by marmosets led to adaptive diversification of callitrichid crania, resulting in a unique facial anatomy. These results further suggest that foraging strategies are adaptively linked to the evolution of callitrichid primates.