Meeting Abstract

9.6  Jan. 4  Changes in the mandible with age in carnivorans BINDER, W/J; Loyola Marymount University wbinder@lmu.edu

As individuals age, skull morphology has been shown to change and reflect new force distributions. This type of change is especially interesting in carnivoran (members of the Order Carnivora) teeth and jaws, as feeding is so important and can have a direct effect upon the bony structures involved. Carnivorans have a single set of adult teeth which are subject to wear over time, and tooth wear results in a decreased force per unit area, which can lower resultant forces at the occlusal bite points. To offset this, the mandibles, under greater strain to eat the same foods with reduced forces at the teeth, may show increased bone thickness to offset these greater loads. Thus both increased age and greater tooth wear in the individuals should correlate with greater bone deposition in the jaw. In addition, this would be expected to be much more prevalent in species which have harder diets (including hyenids, and some mustelids such as the sea otter) than in those with generally mixed or softer diets (ursids and felids). I tested this hypothesis by measuring mandibular cortical bone thickness in individuals from ten species within six families of the Order Carnivora to get a reasonably broad sample. The results seem to confirm the correspondence of increased mandibular cortical thickness with age to a strong degree with measured hyenids and procyonids, and to a lesser degree with felids. No such positive correlation is seen with the measured canids, mustelids and ursids. This may demonstrate the effects of both hardness of diet, which also effects tooth wear, and how limited dietary choices are for older individuals (degree of ominivory).