Meeting Abstract
As gnathostomes diversified, modifications to dental form and mineralized tissue constituents (enamel, dentines and cementum) facilitated a variety of trophic niches. Previous assumptions that non-mammalian tissue-level mechanics of these components had little bearing on whole-tooth functionality. Mammals possess teeth that functionally self-wear and show a diversity of derived tissues which possess unique mechanical attributes. We tested the hypothesis that the material properties of non-mammal dental tissues are uniform. We then explore how those have changed with mammalian cladogenesis and how dietary and dental morphology changes correlate with tissue-level mechanics through the gnathostome radiation. We used microindentation techniques to test dental tissues from representatives of major taxonomic clades, determining Young’s modulus (E), Vicker’s hardness (HV), and crack channeling (CC). These data were mapped onto a phylogeny for Gnathostomata and analyzed in evolutionary and ecological contexts. Results show that properties of non-mammals show substantial intercladal variation. For example enamel E and HV values are low in squamates and neopterygii, and high in chondrichthyans, archosaurs and therians. Non-eutherian enamels isotropically fracture and are prone to catastrophic failure. However, eutherian enamel (excluding cetaceans) exhibits CC associated with enamel prism fabrics, localizing damage. Orthodentine HV and E values mimic the patterns of the enamels, but show greater sub-cladal variability. The results show that dental tissue material property variation in non-mammalian gnathostomes, like mammals is considerable, suggesting that selection acted at the tissue-level to convey differences in tooth functionality throughout the gnathostome radiation.
