Meeting Abstract
The integration of morphology and feeding performance studies can address questions relevant to feeding ecology and evolution. Pinnipeds are a major mammalian lineage with functional innovations for aquatic feeding. Recent functional data show that northern fur seals (Callorhinus ursinus) exclusively use a raptorial biting mode with the greatest gape angle opening velocity reported to date. It appears they are not capable of suction feeding, which is an unusual behavioral trait among extant pinnipeds. Furthermore, northern fur seals are considered to be the most basal living otariid pinniped. The Callorhinus lineage includes several extinct species and due to the craniodental morphological continuum of this lineage, they appear to retain their ancestral otariid feeding mode. We ask, is the feeding mode of Callorhinus indicative of deeper, ancestral feeding behavior among stem pinnipeds? Using 2D geometric morphometrics, we compared the shape of twenty-two fossil stem and crown pinniped mandibles. Sixteen homologous landmarks were digitized using the package Stereomorph in R. Function was then inferred from extant otariid performance studies to stem pinnipeds. Principle Components and Canonical Variates Analyses support the hypothesis that stem pinniped mandible shape does not differ significantly from extant Callorhinus. Therefore, stem pinnipeds likely employed the same raptorial feeding mode used by Callorhinus today, suggesting that Callorhinus retains the ancestral feeding mode through 25 million years of pinniped evolution.
