A comparative anatomical study was conducted among four mobulid species (Mobula japanica, M. munkiana, M. tarapacana, and M. thurstoni), from the coasts of the Gulf of California. Characters of the skeleton (neurocranium, mandibles, scapular girdle, pelvic girdle, and synarcual) were described. Mobula species had a wide structural variation. In the skeleton, M. tarapacana displayed the most plesiomorphic characters, mainly at the cranial level (cranium longer than wide, reduced internasal width, fontanelle longer than wide), while M. japanica had the most derived characters (cranium wider than longer, fontanelle wider than longer). Based on the observations, the dorsal cephalic musculature were similar in all species; however, oppositely to other batoid species, the epiaxilis is strongly developed, as it extends toward the cephalic part of the neurocranium, at level of the postorbital processes. In the ventral musculature, ventral constrictor muscles are quite reduced, whereas complex mandibular muscles are very developed. Muscles showing the highest variation are the coracohioideus and the coracoarcual. Anat Rec, 2007. © 2007 Wiley-Liss, Inc.