Over the past century research on the morphology of the auditory apparatuses of pinnipeds, which include Phocidae (true seals), Otariidae (sea lions and fur seals), and Odobenidae (walruses) is extremely limited, in comparison to other Carnivora. Although, the auditory region and surrounding basicrania are areas that are evolutionarily conservative, most literature is unclear due to mixed terminology, inaccurate information, and indistinct, outdated illustrations. Th e lack of adequate and current studies demonstrates the need for compiling morphological information of the auditory region of modern carnivores in relation to hearing. Auditory terminology will be explored to show morphological comparisons and naming practices among the carnivoran families. By streamlining accurate terminology with straightforward illustrations, the behavioral information gleaned from auditory morphological structures will be clearer even among the diverse members of Carnivora. Th is initial assessment will detail the limited information in prior research on the hearing adaptations for transitional semiaquatic carnivores. Th is preliminary review will help to establish the adaptive patterns (from land to sea) in the basicranial morphology of early pinnipeds, especially in phocids.

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.

There have been many kinds of animals found at Rancho La Brea located in Los Angeles, California; both carnivore and herbivore alike. The most common species found in the tar pits are the predators of the area such as Canis dirus (Dire wolf), Smilodon fatalis (saber‐tooth cat), and Canis latrans (American coyote). Other large carnivores that are not as common but still prevalent include Panthera atrox (American lion), Puma concolor (mountain lion), Panthera onca (jaguar), and Arctodus simus (short‐faced bear). Multitudes of these fossil specimens have been excavated from Hancock Park since the 1870s, and the University of California, Berkeley, was the first institution to house these fossils. Since these early dig operations in the 1900s, University of California, Berekely has traded fossil specimens with other large institutions, including the Field Museum of Natural History located in Chicago, Illinois. It was during a recent visit to the Field Museum to study the La Brea specimens in the Geology collection, that I found a misidentified limb bone. The bone is a humerus which was labeled Aenocyon dirus (Canis dirus). This humerus shows some characteristics that hint toward it belonging to a felid of some kind rather than a large canid. The most likely taxa include Panthera onca and Puma concolor.Grant Funding Source: Nothern Illinois University

Research over the past century is extremely limited 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). An extensive literature review revealed in accurate terminology of this region, incorrect information, mislabeled figures, and details that only correspond to terrestrial taxa. Pinnipeds are unique semiaquatic taxa, possessing adaptations that allow them to hear efficiently both in water and on land. The severe lack of information on this region, as well as nonexistent current studies, demonstrates the need for evaluation and comparison of the auditory morphologies of modern carnivorans in relation to hearing. Initial questions addressed in this study include: comparing the tympanic bulla morphologies of Phocidae to other pinnipeds; comparing distinct morphologies of the tympanic bulla found within phocid subfamilies; and demonstrating any discernable trends in regard to ontogeny or sexual dimorphism. This project explored the morphological correlations of the auditory region of the basicrania of the following representatives of the carnivoran families: Phocidae (including looking at individual subfamilies of Cystophorinae, Monachinae, and Phocinae), Otariidae, Odobenidae, Ursidae (bears), and Mustelidae (weasels). Twelve measurements of the skull and nine calculated ratios were included in multiple principal component analyses (PCA) to determine what areas of the auditory apparatus had the most significant variation in morphology. This is the first study using this type of methodology, especially in reference to the hearing adaptations of pinnipeds, and specifically in phocids. The results of the principal component analyses did exhibit distinct trends in phocid bullar morphology in relation to the other pinnipeds. Phocids tend to have larger tympanic bullar ratios in comparison to other carnivorans and otariids present tympanic bullae that are wider apart and medially parallel. Phocid subfamilial trends include: Cystophorinae on average have wider tympanic bullar ratios; Monachinae have greater distances between their tympanic bullae; and Phocinae overall presents with more generalized morphology. There are distinct trends in the auditory morphology of juveniles (their tympanic bullae make up a greater portion of their skull), but only phocid species that have extreme differences between males and females exhibit distinct morphology within the PCA. To establish more significant trends in ontogeny and sexual dimorphism, more taxa need to be included in future studies. Subsequent studies on auditory morphology will be able to incorporate behavioral hearing information so that a clear, accurate picture of pinniped hearing may emerge. Understanding the modern semiaquatic pinniped ear will help clarify the evolutionary process of aquatic adaptations found within fossil carnivoran taxa, a significant and unknown field of study.

The preservation of fossils in the tar pits at Rancho La Brea makes identification of postcranial material difficult, especially separating Canis lupus form Canis dirus. Generally, distinguishing C. dirus from C. lupus is achieved by study of the dentition and cranial features; otherwise most postcranial bones are identified by size. Because the tar pits at Rancho La Brea disarticulate the remains during the fossilization process, one bony element can rarely be associated with any other. Therefore, another means of identification is needed for postcranial canid materials. I compiled a series of measurements of scapulae, humeri, and ulnae of C. dirus to compare with similar measurements of modern C. lupus. The wolf specimens in this study represent wild populations of North American subspecies that often included sex and age information. By comparing linear measurements of both taxa, I was able to determine statistically relevant differences in the forelimb bone using discriminant function analysis and morphometrics. Being able to provide composite size ranges for individual bony elements, these disarticulated canid specimens of C. dirus and C. lupus can be more accurately identified only from postcranial material. These comparisons can serve as a reference tool for accurately comparing other fossil canid specimens as well as modern species when cranial material is unavailable.