The Chondrocranium of the Mexican Burrowing Toad, \u3cem\u3eRhinophrynus dorsalis\u3c/em\u3e

The chondrocranium of Rhinophrynus dorsalis is described and illustrated. Autapomorphies of R. dorsalis are the presence of the symplectic cartilage and a cartilaginous process on the ascending process of the palatoquadrate. Synapomorphies of Rhinophrynus shared with the Pipidae are: (1) early formation of the lower jaw and (2) presence of a suprarostral plate. Alternative developmental pathways for the formation of the suprarostral plate are considered. Histological data indicates that the suprarostral plate forms from: (1) the early fusion of the cornua trabeculae with the suprarostral cartilages, (2) an anterior growth of the ethmold plate, and (3) subsequent fusion of the cornua trabeculae and the anterior process of the ethmoid plate. The larval crista parotica of R. dorsalis resembles the one described for microhylid taxa