ON THE SPECIALIZATION OF TOOTH MORPHOLOGY IN EARLY CLADODONT SHARKS

Differentiation of tooth shape with jaw position is a well-known pattern in modern piscivorous sharks. This pattern has a functional linkage in both feeding performance and dietary diversity. However, whether specialization of tooth shape was present in early sharks is not known. The objective of this study was to describe tooth shape in early Devonian cladodont sharks, Ctenacanthus and Cladoselache, and test for tooth shape specialization with jaw position. Geometric morphometrics was used to describe tooth shape and resulting axes were regressed with jaw position to test for differentiation with position. Tooth shape did not significantly covary with jaw position in cladodont taxa, however, significant morphometric differences between Ctenacanthus and Cladoselache were evident. Inclusion of two modern taxa with similar niches as the cladodont taxa yielded predictable differentiation of tooth shape with jaw position. The degree of overlap in shape ordination between Ctenacanthus and Cladoselache tooth morphologies may have additional ramifications for positive identification of loose teeth in other paleo work and warrants additional morphometric study.