Charles Ciampaglio (Advisor), Stephen Jacquemin (Committee Member), David Schmidt (Committee Member)
Master of Science (MS)
The extinct Lamniform species, Carcharocles megalodon, were some of the most geographically widespread apex predators in the fossil record. However, whether this cosmopolitan distribution was related to population level differences is unknown. The objective of this study is to assess whether variation in tooth morphology coincided with geographic dispersal. The underlying hypothesis is that variation in an aspect of functional morphology, such as tooth shape, suggests some level of population structuring. Detecting this relationship could potentially provide a mechanism that links population to functional relationships inherent in tooth morphology that may reflect period differences in ocean basins. This would offer a plausible explanation invoking selection as a mechanism for facilitation in their widespread occurrences, while not detecting a difference could have large scale population or selection implications. In this study, we used specimens housed in museum collections to assess morphological variation in upper anterior teeth (lingual view) from several locations spanning the modern day continents 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 ANOVA and MANOVA tests using an oceanic basin of origin as the grouping variable. Teeth from the Pacific and Atlantic Ocean basins were found to covary by geographic region statistically and visually with overlap dependent on the axis. The presence of variation in morphology indicates that there are drivers that differentiate selection of the cosmopolitan species, C. megalodon. A possible explanation of a driver can be analogue to modern Lamniforms, where consistent return to nesting or nursery sights and subsequent philopatry among mating adults would allow for differences. Further, it would be expected that a broader range of spatial selection of samples would also display this outcome; however, more testing with a more spatially diverse data set would be required.
Department or Program
Department of Earth and Environmental Sciences
Year Degree Awarded
Copyright 2016, all rights reserved. My ETD will be available under the "Fair Use" terms of copyright law.