Meeting Abstract
A vital factor of the avian feeding apparatus is cranial kinesis: the mobility of bones within the skull about several key intracranial joints. The underlying patterns among avian jaw muscle and joint function, as well as their implication for ecology and evolution remain largely unknown. Gallinaceous birds vary in size and diet, but feed via pecking and have superficially similar skull morphologies. Thus we expect their jaw muscles and cranial joints to only differ relative to size and the forces loading them. To explore this relationship I built 3D models of five species of galliform and related anseriform taxa and quantified joint size and shape via 3D measurement tools to assess relationships between joint form and function in the complex 3D environment of the skull and found that muscle force and joint surface area expectedly increases as overall skull size does. So far the jaw, otic, and pterygoquadrate joints all scale isometrically, implying that they are under similar biomechanical regimens. However the palatobasal joint scales with positive allometry, suggesting that the relationship between the palate and the braincase may differ across taxa. Even across size and taxonomical differences, galliform cranial muscles have overall parasaggital orientation. This is the first quantitative, comparative analysis of cranial joint function in birds. Future studies will pair these findings with 3D joint force data to better understand the loading environment of the skull. Data from this study will lay groundwork for further studies in the biomechanics and evolution of cranial kinesis in other bird clades as well as in their extinct dinosaur ancestors.
