Meeting Abstract
Vertebrate skulls are three-dimensionally complex structures in which muscles act about joints in complicated ways. The main components of jaw muscle, bite, and joint forces are usually oriented dorsoventrally during biting. However, the mediolateral and rostrocaudal components of forces may be equally important in cranial joints such as kinetic joints or flat-headed animals such as crocodilians. Historically, few studies have captured the three-dimensional relationships between muscle actions and joint forces during vertebrate feeding. Thus, an integrated understanding of the mechanical environment of the skull remains to be fully appreciated. Crocodilians have characteristically high bite forces, likely driven by muscles with significant mediolateral force components, mediated by a series of joints oriented in different axes. We developed three-dimensional, validated free body analyses of the American alligator to estimate bite forces and forces and pressures at key cranial joints including the jaw joint, mandibular symphysis, and pterygomandibular joint to better understand the ontogeny of joint forces within the head. We modeled anatomically accurate jaw muscles, segmented joint surface areas, and using a three-dimensional coordinate system we estimated joint forces and pressures in three canonical axes. This method allows researchers to estimate forces experienced by joints in any system for which muscular PCSA and attachment data are available. These methods will be employed to determine biomechanical patterns during the evolution of crocodyliforms and birds, which rely heavily on secondary articulations which likely experience substantial non-vertical joint forces during feeding behaviors.
