Recent artisanal elasmobranch fishery surveys in the Gulf of California and Pacific coast of Mexico have indicated that batoids are a much moreimportant component of landings than previously estimated. Two butterflyrays, Gymnura crebripunctata and G. marmorata, are recognized in the Mexican Pacific and are among the primary elasmobranchs observed in these landings. The validity of these species was first questioned in 1928, but evidence supporting synonymy has been inconclusive. However, the primary characteristics used to distinguish the species (inter-orbital width and pre-orbital length) are known to be sexually dimorphic features in Gymnura micrura. To determine if G. crebripunctata and G. marmorataare valid species or male and female morphs of the same species, multiple analytical techniques have been applied. Heart and white muscle tissues were collected from fishery-derived specimens in the states of Sonora and Baja California Sur, Mexico. Similarity of the two species was examined through direct sequence comparison and phylogenetic analyses of approximately 445 base pairs of the mitochondrial cytochorme b locus, including other congeners as outgroups. Measurements, vertebral and spiral valve counts were obtained from and and compared to field and museum specimens. We report here on the preliminary results from these analyses.