Koala (Phascolarctos cinereus) dentition and nutrition. I. Morphology and occlusion of cheekteeth



Fermentation of cell wall material in the hind gut of the Koala contributes only 9% of the animal's digestible energy intake. Exposure of the cell contents for digestion in the small intestine depends on an efficient dentition. The molars have been described as selenoid or subselenodont because of the curved cristae originating from the four main cones. Occlusion was reconstructed by wear facet and striation analysis and indicates that contact between the occluding teeth occurs with the cristae shearing past each other, with the lower teeth moving in an antero-lingual direction. The ipsilateral condyle provides the fixed hinge and the arc through which the teeth on the ipsilateral side move explains the orientation of the upper fissures through which the lingual conids pass. Unlike Pseudocheirus with contralateral hinging, and a different arc of movement of lowers, there is no crushing component at the end of the occlusal stroke.