The Muscles of Mastication of Phascolarctos-Cinereus (Phascolarctidae, Marsupialia)

The muscles of mastication of the koala, Phascolarctos cinereus, were dissected, described, weighed and the areas of their origin and insertion were determined. In addition, the temporomandibular joint was described. The aim was to ascertain the relative contribution of those muscles to the jaw movements of the koala. The masseter and temporalis muscles were the principle group and could account for the major movements and forces generated in chewing. In contrast to other herbivorous mammals, the pterygoid muscles were small and probably exert fine motor control over the mandible and temporo- mandibular joints. The digastric and geniohyoid muscles were small, compatible with the limited gape in the animal.