Jaw musculature and jaw mechanics of Sebecus icaeorhinus Simpson, 1937 (Mesoeucrocodylia, Sebecosuchia)

摘要

Sebecus icaeorhinus possessed a narrow, elevated snout and laterally compressed, serrate teeth, unlike modern crocodilians, but superficially similar to those of theropod dinosaurs. Lever arms of the mandibular adductors were generally relatively greater than those of Crocodylus niloticus. Some of the adductors and the depressor mandibulae were relatively larger than in Alligator mississippiensis. Thus Sebecus may have had a stronger bite than the modern forms examined. The form of the teeth suggests use in cutting. Some theropod dinosaurs are similar to sebecosuchians in the possession of relatively deep, narrow snouts and laterally-compressed, serrate teeth. However, the adductor structure was substantially different from that of Sebecus. The presence of muscle and tendon attachments in Sebecus suggests the adductor structure of mesoeucrocodylians is conservative and was established before divergence of the sebecosuchian and neosuchian lineages. No results presented here contradict the interpretation of sebecosuchians as land-dwelling predators.