Amy L. Mork, Walter E. Horton and Christopher J. Vinyard
Both laboratory and field data demonstrate that marmosets gouge trees with wide jaw gapes to elicit exudate flow. Tree gouging distinguishes marmosets from other platyrrhines and presents a natural experiment for studying the morphological consequences of this derived feeding behavior. We utilize comparative histomorphometrics to determine whether loading of the TMJ at wide jaw gapes impacts articular cartilage form in two habitual gouging species, common (Callitrix jacchus) and pygmy marmosets (Cebuella pygmaea), compared to nongouging cotton-top tamarins (Saguinus oedipus) and squirrel monkeys (Saimiri sciureus). Our histological comparisons found no difference in articular cartilage form along the posterior condyle between gouging and nongouging species. Alternatively, the anterior glenoid of gouging species was relatively larger and deeper compared to nongouging species. These findings suggest that the articular cartilage of the anterior glenoid in gouging species possesses improved load resistance ability and points to the mosaic nature of functional responses to tree gouging in the marmoset masticatory apparatus.