95 - Re-evaluation of Phocidae Auditory Terminology, Emphasizing Osteology of the Ossicular Chain and Middle Ear

Poster Board Number: 95
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Abstract Body : Research on the morphology of the auditory apparatuses of pinnipeds, which include the Families Phocidae (true seals), Otariidae (sea lions and fur seals), and Odobenidae (walruses), is extremely limited. Studies on the auditory region and surrounding basicrania revealed evolutionarily conservative features, but most literature remains unclear due to incorrect anatomical terminology, inaccurate information, and indistinct, outdated illustrations. The lack of information on this vital area demonstrates the need for compiling morphological information of the auditory region of modern carnivores in relation to hearing. Clarification of auditory terminology and distinct morphologies will allow direct comparisons of semiaquatic pinnipeds to other completely terrestrial and aquatic carnivorans. An extensive literary survey revealed only a handful of modern anatomical studies on the middle ear ossicles of pinnipeds, otherwise the last anatomical study that included detailed visual representations was from the late 1800s. This study uses new imaging techniques, osteological measurements, and morphological assessment on the middle ear ossicles and the internal auditory anatomy of phocid specimens. Phocid specimen comparisons were made with other terrestrial carnivorans such as Ursidae (bears), Canidae (wolves and dogs), and Mustelidae (weasels) from the Smithsonian National Museum of Natural History (Washington, D.C.) and the Burke Museum (Seattle, WA). Images were processed using specialized photography software for photo stacking. Results confirm that phocid ossicles are extremely derived and specialized for semiaquatic hearing. This level of distinct phocid morphology differs immensely from other terrestrial carnivorans, showing specialized structures even down to the genus level. Currently, it also remains unknown how modern pinnipeds hear in the water at higher frequencies that match those of whales and dolphins. The combination of accurate auditory terminology and new morphological methodology could aid in determining the evolution of semiaquatic hearing and functional specializations of pinniped auditory apparatuses.