CROSS-SECTIONAL GEOMETRIC-PROPERTIES OF THE OTAVIPITHECUS MANDIBLE

Cross-sectional geometric properties of the postcanine mandibular corp us are determined for the only known specimen of Otavipithecus namibie nsis, a middle Miocene hominoid from southern Africa. It is shown that Otavipithecus is unique in that several important mechanical properti es of its mandible, including maximum and minimum moments of inertia a nd distribution of cortical bone, differ from patterns seen in both ex tant hominoids and the early hominids Australopithecus africanus and A ustralopithecus (Paranthropus) robustus. This is particularly apparent in the mechanical design of the posterior portion of the mandibular c orpus for resisting increased torsional and transverse bending moments . Cortical index values at the level of Mt also reveal that both Otavi pithecus and A. africanus are similarly designed to resist increased m asticatory loads with relatively less cortical bone area, a highly eff icient mechanical design. (C) 1996 Wiley-Liss, Inc.