Molecular and morphologic data reveal multiple species in .

DNA sequence and morphometric data were used to re-evaluate the taxonomy and systematics of . Phylogenetic analyses (maximum likelihood and Bayesian inference) of DNA sequences from the mitochondrial cytochrome- gene in 44 samples of indicated 2 well-supported monophyletic clades. The 1st clade contained specimens from Texas historically assigned to ; the 2nd was comprised of specimens previously referable to , , and obtained from northern and eastern Mexico. Levels of genetic variation (~7%) between these 2 clades indicated that the genetic divergence typically exceeded that reported for other species of . Samples of north and south of the Río Grande were not monophyletic. In addition, samples representing and formed 2 clades that differed genetically by 7.14%. Multivariate analyses of external and cranial measurements from 63 populations of revealed 4 morpho-groups consistent with clades in the DNA sequence analysis: 1 from Texas and New Mexico assignable to ; a 2nd from western and southern Mexico assignable to ; a 3rd from northern and central Mexico previously assigned to but herein shown to represent an undescribed taxon; and a 4th from southeastern Mexico assignable to . Based on the concordance of these results, populations from the United States are referred to as , whereas populations from Mexico are referred to as (including some samples historically assigned to , , and ). A new subspecies is described to represent populations south of the Río Grande in northern and central Mexico. Additional research is needed to discern if warrants species recognition.