Meeting Abstract
During gnathostome diversification modifications to dental form and mineralized tissues (enamel, dentines, and cementum) facilitated the exploitation of novel food resources. Generally, it has been assumed that the intra-tissue biomechanics of these constituents had little bearing on whole-tooth functionality, aside from mammalian enamel in occluding dentitions. Many mammals, for example, possess teeth that self-wear to functionality with a diversity of derived tissues—some which possess unique mechanical attributes to resist wear and fracture. Here we formally test the hypothesis that g nathostome dental tissue material properties were static prior to the cladogenesis of Mammalia. Hardness and elastic modulus were tested using two standardized material science techniques, microindentation and nanoindentation, as well as a novel approach for quantifying fracture propagation from indentation cracks. These data were analyzed in a modern phylogenetic and ecological context. The results show these material properties to be highly variable within and between groups. Aside from enamel hardness, there is no significant relationship between most material properties and diet. An ancillary goal of this work is also to glean initial insights about how dental attributes for non-mammalian and mammalian taxa more generally may contribute to whole-tooth form, function, performance, and diet. Complex fracture patterns in the enamels of mammals and chondrichthyans, for example, show that gnathostome lineages independently evolved traits to control fracture and minimize damage. Overall, this study suggests that selection operated at the tissue level to bring about shifts in whole-tooth functionality across Gnathostomata.
