The 82nd Annual Meeting of the American Association of Physical Anthropologists (2013)

Mandibular helical axis during feeding in non-human primates


1Department of Organismal Biology and Anatomy, University of Chicago, 2Department of Community and Family Medicine, Duke University, 3Department of Evolutionary Anthropology, Duke University

Friday 10:15-10:30, Ballroom C Add to calendar

Mandible movement is often described using the three-dimensional displacement of a single landmark. These trajectories, however, depend on the relative location of the point with respect to the center of rotation of the mandible and their interpretation can be equivocal. This problem would be even more important when comparing organisms of different body size. To avoid this, we can describe the mandible movement with traditional kinematic methods such as finite helical axis (FHA). The FHA describes the movement of a rigid object as translating along and rotating around an imaginary axis in space. Previous studies have shown that FHA is located mostly inferior to the temporomandibular joint (TMJ) and that changes its position and orientation continually through the gape cycle. Few data are available regarding the position and orientation of the FHA in non-human primates and it remains unclear to what extent the kinematic patterns of the mandible during feeding vary among primate species. Here we present data on the 3D feeding kinematics of four species of primates (Macaca, Papio, Cebus and Saimiri) obtained by using high-speed video recordings. As previously observed, the FHA was located below the TMJ in all species but the axis orientation changed throughout the gape cycle differently among species. Preliminary analyses show that jaw kinematics of Macaque and Papio are more similar than those of Cebus and Saimiri suggesting clade-specific differences in kinematics. These differences are expected to reflect differences in TMJ morphology as well as differences in patterns of muscle activation.

Funded by the National Science Foundation (BCS 962682)

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