The temporomandibular joint (TMJ), the point of articulation of the lower jaw and the cranium, presents a model system for addressing form and function relationships in primate and mammalian skulls. In the primate group Strepsirhini, the TMJ is highly suitable for consideration of form-function associations because of the marked variation in the TMJ, as well as in the entire jaw. This research will test several functional hypotheses relating TMJ movements and mechanical loading to TMJ morphology in these previously unexamined primate species. Additionally, TMJ form and function in strepsirhines will be compared to haplorhine primates, a second closely-related group of primates. A combined approach using experimental data and comparative measurements will be implemented to assess a number of functional hypotheses. This study will provide the first comprehensive survey of how TMJ form relates to TMJ movements, loading and size-related factors in strepsirhines as well as between strepsirhines and haplorhines. Integration of these new findings with previous research in other primates enables the documentation of evolutionary changes in the TMJ across primates. These evolutionary changes in the TMJ will be compared to temporally correlated changes in the jaw, thus providing an historical perspective to the functional evolution of the primate jaw. Finally, this research develops a protocol for the assessment of fossil primate TMJ functional diversity.
