Brigham Young University Science Bulletin, Biological Series




Examination of the complete musculature of Sceloporus clarki clarki Baird and Girard and seven other species of Sceloporus revealed variation among species of Sceloporus and between Sceloporus and other iguanid lizards. The muscles in which the greatest variation was found were the intermandibularis group, the constrictor colli, the episterno-cleido-mastoideus, the episternohyoideus, the coracoid head of the triceps, the costocoracoid and the flexor tibialis externus. This study indicates: (1) Sceloporus is more closely allied to Crotaphytus than to the ground-dwelling iguanines; (2) the possibility of the basal stock of Sceloporus being arboreal, and (3) Sceloporus is a genus in the process of rapid differentiation.