A Geometric Morphometrics Analysis of the Limb Morphologies of Mosasaurs and Its Palaeoecological Implications

Mosasaurs were a major component of Late Cretaceous marine ecosystems, being the last Mesozoic radiation of secondarily aquatic tetrapods into diverse niches. To shed light on the diversity and evolution of limb morphology in this clade, geometric morphometrics analyses were performed on seven skeletal elements from the forelimb and hindlimb. This study tested the hypothesis tested that mosasaurs living in similar environments would exhibit similar morphologies. After analyzing datasets containing 29 taxa, the observed patterns did not support the hypothesis that habitat was the primary variable influencing morphology. The recurrence of a pattern, the plotting of plioplatecarpine mosasaurs closer to mosasaurine mosasaurs than tylosaurine mosasaurs, which is contrary to phylogenetic expectations in multiple datasets does suggest that relatedness between clades alone does not explain the disparity. In addition, after observing multiple allometric trends for the skeletal elements, a pattern emerged of larger specimens having proportionally less surface area for muscle attachment. It is hypothesized that this is a consequence of differing styles of locomotion.