Aspidoscelis costatus griseocephalus
Sonora, Mexico. August 22, 2011.
A very common lizard in southern Sonora, and they reach an appreciable size. The first one I saw was trapped in an empty swimming pool, on the grounds of my hotel in Alamos. Since then I’ve seen many more at the hotel, and elsewhere. This subspecies is identified by the dark bluish-black chest and venter.