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Gymnurid rays are found in tropical, subtropical, and temperate regions around the world, where they are associated with sandy or muddy bottoms in coastal areas, being easily distinguished from other rays by the width of the disc. In recent years, the systematics of this family have been revised extensively. However, there has been no comprehensive molecular review of the family based on an adequate sample of species and localities, which may have obscured the presence of distinct evolutionary lineages. The present study was based on samples of 12 of the 13 valid species of the genus Gymnura, which were used for a multilocus reconstruction of the evolutionary history of the family Gymnuridae. Our results indicate the existence of several cryptic gymnurid lineages, within the species Gymnura micrura, Gymnura lessae, Gymnura altavela, and Gymnura poecilura. Also, we indicate that only half of the species that compose the genus are known, as well their conservation status. The analyses also indicate that the gymnurids originated during the Paleocene, with events of dispersal and vicariance occurring through the formation of oceanographic barriers, and species diversification peaking during the Oligocene and Miocene. The results of the present study reinforce the need for a comprehensive revision of the systematics of the family, in particular, the widely distributed species that are considered valid taxa, but may, in fact, represent different cryptic species. The inadequate classification of this cryptic diversity may have negative implications for the development of effective conservation measures. [ABSTRACT FROM AUTHOR]

The mullets of the family Mugilidae, and in particular the species of the genus Mugil, are characterized by highly conserved morphological features, which hinder taxonomic classi￠cation considerably. Given this, the present study aimed to evaluate the efficiency of the 5S rDNA gene ^ a rapid and low cost genotyping marker ^ for the discrimination of Mugil species.Variations in the banding pattern permitted the reliable di!erentiation of four species ^ Mugil curema, Mugil incilis, Mugil sp. and Mugil hospes ^ although those of three others (Mugil liza, Mugil platanus and Mugil cephalus) were identical. This suggests that these three forms have diverged very recently, on a time scale that has limitedchanges in the length of the fragments of the 5S rDNA gene. The results of the study con￠rm the e⁄ciency of this marker as a diagnostic tool for the identi￠cation of Mugil species, and its usefulness for population management and pisciculture, an important economic activity involving this group. [ABSTRACT FROM AUTHOR]