Fig. 1. Action of the sternohyoideus (SH) in medial (A) and ventral (B) views. (A) The SH originates on posterior myosepta and the pectoral girdle. Thick ligaments connect the urohyal to the hyoid structure, so that the primary action of the sternohyoideus is to rotate the hyoid about its articulation on the suspensioria, depressing the buccal floor away from the neurocranium and expanding the buccal cavity. Ventral rotation of the hyoid results in depression of the lower jaw through a linkage between the proximal ends of the hyoid and the mandible. (B) Caudal movement also widens the midventral angle of the hyoid, rotating the suspensoria laterally from the neurocranium and laterally expanding the buccal cavity.