The external jaw adductor of amphisbaenids (Reptilia: Amphisbaenia)

Abstract

The structure of the external jaw adductor of Amphisbaena and Trogonophis is reviewed and compared to the external jaw adductor of lizards and snakes. The loss of the upper temporal arch and the development of a closed braincase by frontal and parietal downgrowths allow the origins of the different layers of the external adductor to expand to the temporalis—position of SAVE—SGDERBERGH (1945) in both amphisbaenids and snakes. In both of these two groups, the profundus—and the medialis—layers spread to the temporalisvposition rather than the superficialis— layer. The differentiation of the external jaw adductor took place divergently in amphisbaenids and snakes, however.