Meeting Abstract

56.2  Sunday, Jan. 5 13:45  Variation in Placodont tooth morphology and the effects of structure on tooth function. CROFTS, S. B.; Univ. of Washington, Seatttle croftss@uw.edu

One of the identifying characters of Placodonts, an extinct clade of marine reptiles that lived during the Mesozoic, is the presence of palatal teeth modified to crush hard prey items. The basal most placodont possesses relatively long thin teeth on the palate, maxilla, premaxilla and dentary. In stem lineages, palatal teeth are flattened to form a crushing plate, teeth on the maxilla and the corresponding teeth on the dentary are reduced in number and bulbous in shape, while the teeth in the pre-maxilla and the corresponding dentary teeth remain relatively long, and procumbent. In the crown group this pattern of decreasing tooth number with increased specialization for hard-prey crushing is continued, however, tooth morphology remains diverse. To better understand this tooth diversity, we asked two questions: (1) is there an ideal tooth shape for crushing prey, and (2) how do different shapes withstand these high forces? To determine if there is an ideal shape for crushing prey, we constructed physical models of idealized tooth shapes and tested them on rapid-prototype models of shells. We found that convex teeth, especially those with tall skinny cusps require less force to break shells. We then used FEA to see which of these tooth shapes would be most likely to fail. This study indicated that shapes with tall skinny cusps are the most likely to deform and break. Taking these two studies together indicates that there are functional trade-offs in tooth morphology, and that tooth variation is likely due to differences in diet and the relative importance of tooth.