The Sierra Vizcaíno and Sierra Santa Clara are located along the west coast of central Baja California and compose the continental portion of the Vizcaíno Peninsula. A survey of the herpetofauna of this region documented the presence of several previously unreported species. Three species (Gambelia wislizenii, Coleonyx variegatus, and Crotalus exsul) show a close morphological similarity to conspecifics of Isla de Cedros. The presence of a relict mesophilic species, Hyla regilla, in the Sierra Vizcaíno, suggests that this region was much more mesic in the past. It is hypothesized that the saxicolous taxa of the Sierra Vizcaíno and Sierra Santa Clara colonized these mountains from the Peninsular Ranges of Baja California while the former existed as Pacific islands during the last 10,000 years. Such habitat specialists would be unable to disperse across the flat, sandy, Vizcaíno Desert that currently separates these species from their peninsular counterparts.