Spatial Variation in Tooth Shape of Miocene Populations of Carcharocles Megalodon across Ocean Basins
Carcharocles megalodon is an extinct Lamniform with a historically widespread geographic distribution. However, it is unknown whether this cosmopolitan distribution translated into geographical (e.g. population) level difference in morphology. The objective of this study was to address this question by assessing if variation in tooth morphology coincided with large scale geographic position (i.e. ocean basin). The underlying hypothesis is that tooth shape variation is an aspect of functional morphology that can be selected through a combination of genetic and environmental factors. Detecting a relationship would provide some evidence of population structuring and suggest a functional relationship inherent in tooth morphology. In this study, we used specimens housed in museum and private collections to assess morphological variation in upper and lower anterior teeth from several locations from the Atlantic coastlines of North America and the Pacific coastlines of North and South America. We used geometric morphometric techniques to describe tooth morphology and specifically tested for geographic differences in tooth shape by extracting morphometric axes from relative warp analyses and subjecting these axes to MANOVA and ANOVA tests using Atlantic vs. Pacific basin of origin as the grouping variable. Overall, teeth from the Atlantic and Pacific Ocean basins were found to covary by geographic region statistically and visually In addition, tooth size was found to relate to morphology. Interactions between size and basin were also recovered. The presence of variation in morphology suggests that there are selective agents driving this pattern. Possible explanations could be analogous to modern Lamniformes, where diet variability depends on the availability of prey, or mating patterns consistent with return to nursery sights and subsequent philopatry among mating adults. This study represents an initial step in discerning morphological variability in C. megalodon but a broader range of sites from across the globe is warranted for future studies.
Bertsos, M. J.,
& Jacquemin, S. J.
(2017). Spatial Variation in Tooth Shape of Miocene Populations of Carcharocles Megalodon across Ocean Basins. Southeastern Geology, 52 (4), 179-194.