Meeting Abstract
88.4 Wednesday, Jan. 7 Aprismatic enamel microstructure and tooth sharpness in odontocetes: economy or adaptation? BEATTY, B.*; WERTH, A.; WOOD, C. B.; New York College of Osteopathic Medicine; Hampden-Sydney College; Providence College bbeatty@nyit.edu
The evolution of enamel microstructure in cetaceans has been characterized as an early, simple reversal to the aprismatic condition considered plesiomorphic to mammaliaforms. Odontocete dentitions in particular are generalized as having simplified enamel microstructure, occlusion (non-occlusal, only interdigitating), and tooth morphology (peg-like, homodont). These are all interpreted as the result of a single modification from mastication to raptorial prey-capture and/or suction feeding. Our study of enamel microstructure, tooth sharpness, and gross dental wear of odontocetes and several archaeocetes allow identification of a positive, complex relationship between heterodonty (apomorphic in some), enamel microstructure, and dental wear (not simply breakage). Enamel thickness, the presence and type of prisms, and absence of Hunter-Schreger bands correlate with some loss of occlusal function. Breakage is evident among taxa that have thin and/or less prismatic enamel, such as Delphinapterus, but have returned to more damaging diets (sarcophagy). The generalizations of odontocetes as homodont and non-masticating are not applicable to the whole clade. Rather, a continuum exists in which some members continue some ancestral dental function to the present day, whereas others autapomorphically lose masticatory ability. When sarcophagous taxa are excluded, a negative relationship between sharpness and prismatic enamel is evident, suggesting the loss of prismatic enamel may have been an adaptation for increasing sharpness in odontocetes. Moderate homodonty and polydonty of toothed mysticetes indicates that some of these changes occurred before the split of the Odontoceti and Mysticeti. More fossils of stem Neoceti are needed to clarify the polarity of these changes.
