From Land to the Water: A Comparative Look at the Morphologies of the Auditory Apparatuses of Carnivores

Abstract

Morphological characters have been the basis for determining evolutionary relationships among mammalian carnivores and continue to be important in that regard. For the animals that make up the families Phocidae (true seals), Otariidae (sea lions and fur seals), and Odobenidae (walruses), together known as Pinnipedia, the research is very limited on the morphology of their auditory apparatuses. In regard to the few auditory characters that are well studied, they are almost always used for phylogenetic analyses. The reasoning behind their use in these analyses is that there is disagreement as to how pinnipeds evolved: do pinnipeds have a monophyletic or a diphyletic origin? To aide in answering this overall question of phylogeny this study plans to establish the morphology of characters of the auditory region and surrounding basicrania, to determine some of the processes in which auditory characters evolved due to a return to water, and if any of these characters have a phylogenetic signal. Some of the preliminary results include some osteological measurements of both extinct and extant specimens and CT scans of specific semiaquatic carnivoran skulls. One of the CT scans included the extinct seal Devinophoca emryi (early‐middle Miocene, ~16 Ma), which is known to have a mixture of primitive and derived characters in the skull and postcrania. Preliminary observation of the basicranium and auditory region demonstrates a mixture of primitive and derived characters as well. Overall, the comparative morphology of Pinnipedia ossicles and other derived auditory characters can possibly retain high phylogenetic signal even with the adaptive pressures of the aquatic environment. This information will aid in the overall understanding of phocid evolution and hearing adaptation during the transition from land to water.