Meeting Abstract
Gars provide valuable insight into the origins of plesiomorphic actinopterygian and osteichthyan feeding systems, but as rapid, lateral-snapping ambush predators, their own feeding system is highly derived. This study investigates the function of gar-specific specializations, such as horizontally-oriented palates, mobile pectoral girdles, and platyrostral skulls, that enable a surprising degree of cranial kinesis during feeding. To assess skull kinematics, we captured high-speed video of feeding in the alligator gar, Atractosteus spatula, and documented new anatomical features using contrast-enhanced computed tomography. This study reveals a system of coordinated interactions between the mandibular arch, hyoid arch, and pectoral girdle that produce rapid jaw movements and precisely timed buccal and pharyngeal expansions for the controlled movement of water. During a lateral strike, flat plate suction due to jaw opening and neurocranial elevation draws prey inward before hyoid depression begins. Hyoid depression is delayed by the line of action of the sternohyoideus and activity of the hyoid constrictors. The line of action of the sternohyoideus changes towards the conclusion of jaw opening due to neurocranial elevation and rotation of the pectoral girdle, resulting in pharyngeal expansion via hyoid depression, suspensorial abduction, and jaw adduction. This produces an anterior to poster flow of water during the feeding strike. Alligator gars demonstrate how a rapid, lateral-snapping feeding mechanism can utilize flat plate suction and delayed pharyngeal expansion to its advantage. These findings have implications for other platyrostral taxa, particularly fossil stem-tetrapods, that convergently evolved many similar morphological features as gars.
