QUESTIONING GRAY SHARK BIODIVERSITY IN THE ATLANTIC COASTAL PLAIN: MORPHOMETRIC ANALYSIS OF MIOCENE-PLIOCENE SHARK TEETH
Preliminary analysis used five hundred carcharhinid upper teeth, which are the most commonly used in taxonomic studies. Each tooth was digitally photographed and x-y coordinates of geometrically and biologically identifying characteristics, ten lingually and nine labially, were obtained. Procrustes method was used to simultaneously fit the landmark points and derive shape coordinates that are invariant in respect to variations in size, rotation, and position of specimens. Principle component ordination of the Procrustes tangent coordinates was used to compare the overall, allometryfree shape differences between the teeth from different formations and geographic location. A separate size analysis was completed using tooth width and centroid size. Preliminary analysis reveals insignificant allometry-free morphological and size variation suggesting that tooth morphology remained constant throughout the Miocene and Pliocene. The gradational variation observed in the sampled teeth suggests that these specimens represent a morphological gradient rather than many discrete species. This implies that carcharhinid species diversity of the ACP cannot be determined based on isolated teeth. In addition, the temporal stability of shape morphospace suggests slow rates of morphological change of shark teeth during the Miocene and Pliocene.