SPECIES DISCRIMINATION IN CARCHARHINUS SHARK TEETH USING ELLIPTIC FOURIER ANALYSIS

Sharks of the genus Carcharhinusare commonly represented in fossil assemblages by isolated teeth. Neogene fossil teeth from this genus have been identified by many authors as belonging to extant species. Their identification, however, is particularly challenging due to similarities in tooth shape among species. Many informative diagnostic characters for species identification in modern specimens, such as tooth row counts, vertebral counts, and external morphology, are not applicable to isolated teeth. Therefore, improved methods of species identification based on isolated teeth are essential for a better understanding of the evolutionary history of the genus.

This study tests the ability of elliptic Fourier analysis to discriminate among the upper teeth of fourteen modern species of Carcharhinus. The elliptic Fourier analysis was performed on outlines captured from digital images of the lingual tooth face. The resulting elliptical Fourier descriptor coefficients were then subjected to a principal components analysis, and a canonical discriminant analysis was performed on the principal component values. Cross-validation demonstrates the discriminatory ability of this method, with over 80% of teeth being correctly identified to species. Lateral tooth positions were most likely to be correctly identified. These results indicate that modern species of Carcharhinus can be distinguished by the shapes of their teeth. Similar morphometric analyses may allow for the discrimination of fossil species of Carcharhinus.