Melanorivulus
Melanorivulus is a genus of South American freshwater fish in the family Rivulidae. Most species are endemic to the Río de la Plata, eastern Amazon (west to Tapajós basin), Tocantins–Araguaia and São Francisco basins in Brazil, but a few members of this genus range west into Bolivia, south into Paraguay and Argentina, and east to Parnaíba and Sergipe in northeastern Brazil. Only "M. schuncki" occurs north of the Amazon River. They inhabit shallow waters, generally deep, at the margins of streams in open or fairly open habitats like the Cerrado or Cerrado–Amazon transition. Many have tiny ranges  and are seriously threatened. Similar to closely related genera such as "Anablepsoides", "Atlantirivulus", "Cynodonichthys" and "Laimosemion", "Melanorivulus" are jumpers and non-annual killifish. "Melanorivulus" are small fish, with the largest species up in total length and the smallest less than . They are often quite colorful and some are kept in aquariums. Species. Until 2011, "Melanorivulus" were included in "Rivulus", and some prefer to maintain them in that genus. If recognized as a valid genus, there are currently 60 species in "Melanorivulus":