Abstract
Cranial anatomy and swallowing behavior of the yellow rat snake, Elaphe obsoleta quadrivittata, were examined. The alternating motions of each side, ipsilateral and contralateral, establish a regularly repeated swallowing cycle advancing the jaws along the swallowing axis until eventually contractions of neck muscles take over to complete swallowing. Six marked points on the skull were followed in lateral view by cineradiography and their displacements and accelerations compared. Alternating head swings carry the cranium through swallowing angles that decrease sharply soon after swallowing begins and well before the widest portion of the prey is reached by the jaw angles. The bunching of internal prey may require this early change in swallowing angle. Features of jaw kinematics such as head swivel, jaw movement, and lateral flaring of mandibular joints, serve to shape and accommodate bulky prey. The ectopterygoid controls actual motion of maxilla, placing it at an oblique angle, to ensure that upon closing its rear teeth are first to engage the prey. The palatomaxillary arch retracts late in close phase. Forces developed during retraction play only a small role in actually moving prey into the mouth. Instead, the swallowing progress is achieved more by the advance of the jaws along the prey.
