Phylogenetic relationships of the whiptail lizards of the genus Cnemidophorus are inferred based on a combined analysis of mitochondrial DNA, morphology, and allozymes. Within the Teiini, Teius and Dicrodon are the most basal lineages, and these two taxa form a graded series leading to a cnemidophorine clade containing Ameiva, Cnemidophorus, and Kentropyx. Cnemidophorus monophyly is not supported, with members of the neotropical “C” lemniscatus species group (except “C” longicaudus) being more closely related to species in other neotropical cnemidophorine taxa (Ameiva and Kentropyx). Ameiva is also paraphyletic.The “Cnemidophorus” lemniscatus species group is also paraphyletic, with a “C” murinus “C” lemniscatus complex clade being more closely related to Kentropyx than to “C” lacertoides, “C” longicaudus, and/or “C” ocellifer. Although the “C” lemniscatus species group is paraphyletic, the three remaining bisexual “Cnemidophorus” species groups (deppii, sexlineatus, and tigris species groups) are each monophyletic. Together, these three groups form a clade (= North American “Cnemidophorus” clade), with the deppii and tigris species groups being sister taxa. Within the “Cnemidophorus” deppii species group, the Baja California “C” hyperythrus is the sister species to a more exclusive mainland Mexico clade containing “C” deppii and “C” guttatus. Except for a “C” inornatus “C” sexlineatus clade and a monophyletic “C” gularis complex, the inferred inter- and intraspecific relationships within the sexlineatus species group are weakly supported. In none of the inferred phylogenies are the “C” costatus populations (“C” c. costatus and “C” c. griseocephalus) represented as each other's closest relatives.Because of Cnemidophorus paraphyly, nomenclatural changes are recommended. Aspidoscelis Fitzinger, 1843, is resurrected for the North American “Cnemidophorus” clade containing the deppii, sexlineatus, and tigris species groups (and the unisexual taxa associated with them). Lizards of the genus Aspidoscelis differ from all other cnemidophorine lizards by the combined attributes of absence of basal tongue sheath, posterior portion of tongue clearly forked, smooth ventral scutes, eight rows of ventral scutes at midbody, absence of anal spurs in males, mesoptychial scales abruptly enlarged over scales of gular fold (more anterior mesoptychials becoming smaller), three parietal scales, and three or four supraocular scales on each side.Previous studies using morphology and allozymes have determined that the unisexual Kentropyx borckiana originated from a historical hybridization event between the bisexual species K. calcarata and K. striata. In this study mitochondrial DNA confirms K. striata as the maternal ancestor of K. borckiana.A review of our current knowledge of teioid unisexuals and their hybrid origins is provided. Also, a reevaluation of teiine chromosomal evolution is presented from a phylogenetic perspective. These reviews elucidate the paradox that the capability of instantly producing parthenogenetic clones through one generation of hybridization has existed for approximately 200 million years, yet the extant unisexual taxa are of very recent origins. Consequently, these lineages must be ephemeral compared to those of bisexual taxa.