Morphology and function of the feeding apparatus in Dermophis mexicanus (Amphibia: Gymnophiona)

Abstract

The morphology and mechanics of feeding in Dermophis mexicanus were studied using descriptive anatomical, cinematographic and electromyographic approaches. The lower jaw has a retroarticular process extending one-third of the total jaw length, and an articulation that restricts anteroposterior movements. Muscles from three anatomically distinct sites, the temporal fossa, the lateral surface of the neck, and the subvertebral region, act to execute the bite during feeding on earthworms. Muscles in the first of these sites are comparable to the jaw adductors of other vertebrates, while those in the second two represent morphological and functional departures. The large interhyoideus muscle and the elongate retroarticular process are modified to function in jaw closing. The longus capitis muscles appear to act to depress the cranium at the cranio-vertebral joint, a motion that occurs simultaneously with maximum jaw closing. The latter two muscles appear to have greater importance for feeding in Dermophis than do the temporal adductors, and the evolution of this specialized arrangement may be related to the demands for a reduced cross-sectional area of the head in these burrowing vertebrates.