Great Basin Naturalist


An extant, indigenous desert tortoise population is reported from the cape region of Baja California Sur, Mexico. This population is described and figured as a new species, Xerobates lepidocephalus, distinct from all other North American tortoises including Xerobates agassizii, X. berlandieri, Gopherus flavomarginatus, and G. polyphemus. Xerobates lepidocephalus, or the scaly-headed tortoise, whose range is known only from an extremely small area in the gulf-drainage mountains just south of La Paz, appears to be a peninsular relict whose closest living relative is probably X. agassizii. However, carpal bone affinities connote a close relationship between X. lepidocephalus and the Oligoeene species X. laticunea from Wyoming and Colorado, suggesting that the former species may be one of the more primitive contemporary tortoises of the Xerobates lineage. Such evidence indicates that X. lepidocephalusis not of vicariant origin resulting from the formation of the cape of Baja California. Scaly-headed tortoises likely ranged, and may yet be discovered, in other medium-elevation mountain ranges of the cape.