Jaw dimensions and torsion resistance during canine biting in the Carnivora

Abstract

Carnivoran skulls can be functionally modelled as intricate half-cylinders. When a single canine meets resistance during biting, the jaw becomes asymmetrically loaded and the maximum torsional strains lie along helices on the surface of the skull that are positioned at 45° to the twisting forces. The integrity of the skull as a whole is conserved by the innate stability of its overall tubular shape. Strengthening structures, if needed, are expected to be concentrated along these helices. Our analysis predicts that the amount of bone needed to form the skull can be significantly reduced if the dimensions of the jaw are restricted such that the length to width ratio is less than or equal to π/2. Measurements of a sample that includes most of the modern genera of the Carnivora, as well as some extinct forms, all conform to this prediction.