Geometric morphometrics support the proposed molecular taxonomy for three Eucinostomus species (Perciformes: Gerreidae) along the coasts of Mexico

The genus Eucinostomus Baird 1855, is the most diverse and taxonomically complicated group of the family Gerreidae in the Neotropics. Since its diagnosis the specific composition of the genus has been controversial. This genus is limited to the tropical and subtropical America, except for one species, the Atlantic flagfin mojarra E. melanopterus (Bleeker 1863), which also occurs along the eastern Atlantic. Otherwise, the silver mojarra E. argenteus Baird & Girard 1855, is the only species that has been cited as inhabiting both coasts of the American continent, although several authors have denied its occurrence in the tropical eastern Pacific. Besides, Dow’s mojarra, E. dowii (Gill, 1863), inhabitants of the tropical eastern Pacific are considered by some authors as synonymous for E. argenteus, and this latter species, at the same time, has been confused with other tropical eastern Pacific species: the dark-spot mojarra E. entomelas Zahuranec in Yáñez-Arancibia, 1980). Recently, molecular analyses provided evidence for these three Neotropical Eucinostomus species that show strong divergence, as would be expected between any pair of marine fish species. To evaluate the morphological evidence of these species along the coasts of Mexico and compare the results from different identification techniques, these species were sampled throughout their range in Mexico. Geometric morphometrics revealed that each species is morphologically distinct, confirming the evidence from sequences of DNA that they are not synonymous, but different evolutionary entities. A new combination of biometrical traits is presented to permit unambiguously identify the species.