Meeting Abstract

67.5  Tuesday, Jan. 6  The role of the fronto-parietal sinus during bone-cracking in spotted hyenas TANNER, J. B.*; DUMONT, E. R.; SAKAI, S. T.; LUNDRIGAN, B. L.; HOLEKAMP, K. E.; UMass, Amherst; UMass, Amherst; Michigan Sate Univ., E. Lansing; Michigan Sate Univ., E. Lansing; Michigan Sate Univ., E. Lansing jtanner@bio.umass.edu

The ability to break open large bones has evolved independently in only three groups of carnivorous mammals, all of which have robust teeth, vaulted foreheads, and pronounced sagittal crests. One unusual skull feature, present in bone-cracking members of the family Hyaenidae, is a caudally elongated frontal sinus that extends into the parietal bone and along the length of the sagittal crest. It has been hypothesized that this sinus functions to resist bending and dissipate stress during bone-cracking. Here we used Finite element analysis (FEA) to examine patterns of stress distribution in the skull of a spotted hyena (Crocuta crocuta) during unilateral biting, and to inquire about the functional role of the fronto-parietal sinus in stress dissipation. We constructed and compared three FE models: 1) a normal model of an adult Crocuta skull; 2) a model in which the caudal portion of the fronto-parietal sinus was filled with bone; and 3) a model in which the sagittal crest was flattened to resemble the plate-like crests of other mammals. During biting, an arc of decreasing stress extended from the bite point up through the vaulted forehead and along the sagittal crest. Our results suggest that pneumatization of the hyenas skull both enhances its ability to resist bending, and together with the vaulted forehead, plays a critical role in evenly dispersing stress away from the facial region during biting. The highly specialized skulls of bone-cracking hyenas are thus able to meet the concurrent demands of generating large bite forces while distributing large stresses.