Occlusal Movements of the Brushtail Possum, Trichosurus-Vulpecula, From Microwear on the Teeth

Abstract

This study characterises the jaw movements of the brushtail possum, Trichosurus vulpecula, from an analysis of microwear on the premolar and molar teeth. From 10 skulls of T, vulpecula, micrographs of tooth replicas which exhibitied progressive degrees of dental wear were examined for the location of wear facets and the orientation of striae on them. These data were transferred to transparencies overlying occlusal photographs of the jaws. Two movements, a vertical sectorial movement in the premolars segment and an anteromedial shearing and grinding stroke in the molar segment, were inferred. The directions of wear striations with respect to the sagittal plane supported the concept that the mandible rotates around the contralateral condyle from the working side. No evidence of balancing contact facets were found on the teeth of the contralateral side, in agreement with an anisognathous jaw movement. Videoradiographic observations of the chewing cycle of one brush-tailed possum confirmed that puncture crushing is employed early in the chewing cycle, followed by an anisognathous labiolingual transit of the mandibular molars. However, the resolution of the condyle by videoradiography was insufficient to determine the point of rotation of the jaw movements.