A new miniature killifish of the genus Melanorivulus (Cyprinodontiformes: Rivulidae) from the coastal plains of north-eastern Brazil

Abstract

Melanorivulus atlanticus, new species, is described on the basis of specimens collected in the coastal plains of north-eastern Brazil, constituting the first record of the genus for the Atlantic Forest biogeographical province. The new species together M. decoratus and M. jalapensis form a clade of small species, not surpassing 20 mm SL, mainly diagnosed by the presence of five branchiostegal rays. Melanorivulus atlanticus differs from those two species by a narrow black border along the entire caudal fin in males and the presence of 2 + 1 neuromasts in the mandibular series, besides differing from all congeners by having sexually dimorphic pelvic fin, which is pointed and with seven rays in males, elliptical and with five rays in females. The description of M. atlanticus expands in 670 km to east the known geographic range of the genus.