Five subspecies of Ctenosaura hemilopha are recognized, including C. h. hemilopa from Baja California; C. h. insulana from Isla Cerralvo, Gulf of California; C. h. conspicuosa from Isla San Esteban and (?) Isla Lobos. Gulf of California; and two new subspecies: C. h. macrolopha from Sonora and northern Sinaloa, and C. h. nolascensis from Isla San Pedro Nolasco, Gulf of California. The species is thought to have evolved from C. pectinata, through the somewhat similar C. h. macrolopha or its forerunner. Its range probably extended at an earlier time northward around the Gulf of California, thence southward through Baja California, with populations reaching certain Gulf islands from the peninsula, not from mainland Mexico, despite greater proximity of some of the islands inhabited to Sonora than to the peninsula.
Smith, Hobart M.
"The Sonoran subspecies of the lizard Ctenosaura hemilopha,"
Great Basin Naturalist: Vol. 32
, Article 6.
Available at: http://scholarsarchive.byu.edu/gbn/vol32/iss2/6