Two new species of (Cricetidae: Neotominae) from the Transverse Volcanic Belt of Mexico.

Specimens of the species group distributed in the western and northeastern montane regions of Michoacán, México, historically have been assigned to . Previous studies indicated that these specimens possessed mitochondrial DNA haplotypes that were distinct from both and , a recently named species in the species group from northeastern Michoacán and western Morelos. Herein karyotypic, DNA sequence, and morphological data were analyzed from those populations to evaluate their taxonomic affinity. Karyotypic data indicated that individuals from western Michoacán (Dos Aguas and Aguililla) and from a newly discovered population in northeastern Michoacán (Zinapécuaro) were chromosomally similar to (FN = 68) but distinct from other taxa assigned to the species group. Analyses of cranial characteristics indicated that, relative to other species in the species group, two morphologically distinct groups were present that corresponded to the Dos Aguas/Aguililla and Zinapécuaro populations, respectively. The latter population, although represented by a small sample size ( = 5 specimens), appeared to exhibit some trenchant morphological distinctions compared with other cryptic species in the group. Phylogenetic analyses (parsimony, Bayesian, and likelihood) of DNA sequences obtained from the mitochondrial cytochrome- gene indicated that although the individuals from Dos Aguas/Aguililla and Zinapécuaro formed a sister group relationship, they formed monophyletic clades that differed genetically (2.54%)-a level approaching that seen between other sister species of . Further, the Dos Aguas/Aguililla and Zinapécuaro clade was more closely aligned with a clade containing representatives of . and . instead of with those from closer geographic proximities (. ) located in eastern Michoacán. Together, these results indicated that these two populations seemingly represent two undescribed species in the species group for which we propose the names for populations in western Michoacán (circa Dos Aguas and Aguililla) and for populations in northeastern Michoacán (circa Zinapécuaro).