61 - Osteological Correlates of Fascicle Length and Gape Across Carnivora

Poster Board Number: 61
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Co-authors:

Arin Berger - Department of Biological Sciences - North Carolina State University; Lara L. Martens - Department of Biological Sciences - North Carolina State University; Adam Hartstone-Rose - Department of Biological Sciences - North Carolina State University

Abstract Body : Mammalian masticatory anatomy has been evolutionarily shaped by dietary demands, such that the myological and osteological components of this anatomy may reflect dietary specializations. Jaw gape, a key parameter that influences dietary choice, is constrained by both myology and osteology and is inversely proportionate to bite force. During prey acquisition and ingestion, individuals must be capable of producing adequate gape while also producing the necessary force for killing and processing. Previously, we found a correlation between masticatory adductor fascicle lengths (FLs; a correlate of gape) and dietary size in carnivorans, particularly within Felidae and Musteloidea. Although we have previously confirmed osteological proxies for both myological and osteological components of bite force, we do not yet have similar proxies for gape; however, such proxies would allow paleontologists to reconstruct gape capabilities (potential correlates of prey size) in extinct carnivorans. Here we evaluate the correlation between osteological proxies and chemical dissection-based FLs for three individual masticatory adductor muscles – temporalis, masseter, and medial pterygoid – and an average FL for the adductor complex for a sample of Canidae (n = 10), Musteloidea (15), Ursidae (4), Felidae (11), and 2 other feliforms. We assess the correlation of 17 potential origin-to-insertion as well as 28 cranium- and mandible-only osteological proxies across the order as a whole as well as subsets of taxa within it. Additionally, we present for the first time maximum bony gape (MBG) – a non-behavioral estimate of gape that accounts for only osteological constraints but may correlate with behavioral gapes – for a large and diverse carnivoran sample and assess its correlation with dietary size and mechanical properties. We found well correlated osteological proxies of FL for complete skulls, but also for crania and mandibles alone, making gape reconstruction equations useful even for many partial carnivoran fossils. However, the best correlated proxies differ between taxa. While temporalis proxies were largely best correlated to average FL for the complex, across individual muscles, we found that although the temporalis is the largest masticatory adductor, the best osteological proxies were found for masseter FL. This is perhaps because of the neuro-protective functions of the cranial vault where temporalis originates and many of the fascicles insert on a central tendon, while the origin to insertion region of the masseter is almost entirely influenced by masticatory function. Additionally, we found MBG was correlated with dietary size in feliforms and differed between generalist and soft-diet specialist caniforms as well as hard- and soft-diet specialist musteloids.