THE STRUCTURE OF THE MANDIBULAR CORPUS AND ITS RELATIONSHIP TO FEEDING BEHAVIORS IN EXTANT CARNIVORANS

Assuming some optimization of bone structure to applied mechanical loadings in vivo, different killing and feeding behaviours in carnivores should be reflected in observed differences in cross-sectional shape of their mandibular corpora. Section moduli are used to gauge the magnitudes of bending moments in the mandibular corpus and, when dentary length is controlled, the magnitudes of forces applied to the corpus. Comparisons are made of section moduli at the P3P4 and P4M1 interdental gaps among canids, felids and hyaenids; in canids only, the M1M2 interdental pp was also studied. Local variations in loadings are identified by comparing the section moduli at adjacent loci along the corpus within each family. The findings of this study show that the precarnassial corpora of canids and hyaenids have greater strength in bending than the corpora of felids of similar body weight. This is taken to reflect relatively greater bending moments under loading in the corpora of canids and hyaenids due, in part, to their elongate dentaries (relative to body weight). Relative to dentary length, however, the precamassial corpora of felids and hyaenids have much greater strength in bending than the corpora of canids. These scaling relationships appear to reflect the high customary forces (i.e. not moments) applied to the precamassial corpora of felids and hyaenids with sustained canine killing bites and with bone ingestion using the premolars, respectively. An increase in bending strength of the corpus caudal to the carnassial blade in canids is interpreted to be an adaptation for bone-crushing with the postcarnassial molars.