The genus Menticirrhus is widely distributed in the Neotropical region, where its species are common and abundant in shallow coastal waters and estuaries. The diversity, biogeography, and evolutionary relationships of the Menticirrhus species are still poorly known, due primarily to the difficulty of differentiating the species, given the broad similarities in their external morphology. The present study is based on the analysis of morphological and molecular data, with the examination of type specimens and a comprehensive collection of non-type specimens from an ample geographic range. These analyses indicated that two widely distributed Western Atlantic species, Menticirrhus americanus and M. littoralis, represent species complexes. The M. littoralis species complex is characterized by the absence of dark bars on body side, and a smaller, light-colored pectoral fins, that barely reachi...