Performance of shark teeth during puncture and draw: implications for the mechanics of cutting

The performance of an organism's feeding apparatus has obvious implications for its fitness and survival. However, the majority of studies that focus on chondrichthyan feeding have largely ignored the role of teeth. Studying the functional morphology of shark teeth not only elucidates the biological role that teeth play in feeding, but also provides insight specifically into the evolution of shark feeding because teeth are often the only structures available in the fossil record. In the present study, we investigate the puncture and draw performance of three general categories of extant teeth, tearing-type, cutting-type, and cutting-clutching type, as well as three fossil morphologies, utilizing a universal testing system. Differences in puncturing performance occurred among different prey items, indicating that not all 'soft' prey items are alike. The majority of teeth were able to puncture different prey items, and differences in puncture performance also occurred among tooth types; however, few patterns emerged. In some cases, broader triangular teeth were less effective at puncturing than narrow-cusped teeth. There were no differences between the maximum draw forces and maximum puncture forces. Many of the shark teeth in the present study were not only able to perform draw and puncture equally well, but also many tooth morphologies were functionally equivalent to each other. The findings obtained in the present study lend little support to the belief that shark tooth morphology is a good predictor of biological role.