Shape variation in the mandibular symphysis of apes: an application of a median axis method.

Symphyseal contours in a sample of living and fossil apes were assessed by application of the line skeleton, a form of median axis transformation. While the line skeleton offers novel opportunities for the analysis of shape, this study reaffirms previous observations that the shape of the symphysis is highly variable within great ape species, such that symphyseal morphology is not useful as a taxonomic marker. There is also little indication that symphyseal shape differs significantly between the sexes. The perception of what constitutes a salient superior or inferior transverse torus among living apes appears to be dependent on the expression of the genioglossal fossa.