Meeting Abstract
Reptiles rarely approached the biomechanical sophistication of feeding or dietary diversity seen in mammals. Their teeth are typically non-occluding structures with simplistic architecture. Conversely, most mammals possess teeth that are drawn across one another during mastication, self-wear to their functional morphology and are composed of prismatic enamel. Among the most sophisticated prism architectures is the modified radial enamel (MRE) of grazing ungulates whose coarse tooth surfaces enable the grinding of tough, abrasive laden plant matter. MRE conveys exceptional fracture toughness and controlled fracture propagation. Hadrosaurid dinosaurs independently evolved self-wearing grinding dentitions and possess wavy enamel (WE), composed of folded layers of hydroxyapatite crystals. We tested the hypothesis that WE served an analogous biomechanical role to MRE. We: 1) tribologically modeled the effects of enamel fracture on hadrosaurid occlusal surfaces; 2) introduced enamel fractures to teeth from hadrosaurids, archosaurian outgroups, and horse and bison, 3) documented crack patterns; and 4) contrasted the results with regard to occlusal morphology and dietary inferences. Enamel removal leads to aberrant self-wear to hadrosaurid chewing pavements. Non-wavy enamels show isotropic fracture patterns and catastrophic enamel shell damage. WE limits damage to the enamel crests through energy-robbing crack deflection at kinks in the enamel fabrics and channeling perpendicular to the enamel-dentine junction like the teeth of grinding ungulates.
