Graduation Year

2008

Document Type

Dissertation

Degree

Ph.D.

Degree Granting Department

Biology

Major Professor

Philip J. Motta, Ph.D.

Co-Major Professor

Daniel C. Simkins, Jr., Ph.D.

Keywords

Elasmobranchii, Functional morphology, Feeding, Performance, Finite element analysis

Abstract

Measuring the effects of morphology on performance, and performance on fitness, is necessary to gain a full picture of selection, adaptation, ecology, and evolution. The performance of an organism's feeding apparatus, of which teeth are an integral part, has obvious implications for its fitness and survival. Extant shark teeth encompass a wide variety of shapes, and are often ascribed qualitative functions without any biomechanical testing, employing terminology such as gripping, piercing, crushing, cutting, or tearing. Additionally, teeth also comprise the vast majority of the fossil record of sharks. Therefore to understand the evolution of the shark feeding mechanism, we must understand the contribution of all parts of the feeding apparatus, including the teeth. Performance testing of extant and extinct shark teeth, nanoindentation of shark teeth, finite element analysis of tooth morphology, and phylogenetically informed analyses of shark tooth morphology and ecology were employed to elucidate the relationship between performance, ecology, and evolution. Performance testing of teeth in puncture and draw revealed few morphological patterns, indicating that most morphologies are functionally equivalent. Finite element modeling of teeth in puncture, draw, and holding showed that shark teeth are structurally strong and unlikely to fail during feeding. Evolutionary analyses of tooth shape and ecology showed no relationship between morphology, habitat, and diet. These results have significant implications for the shark paleontology, where the shapes of shark teeth are used to make assumptions about ecology and evolution.

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