Melanorivulus is a genus of South American freshwater fishes 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:
Melanorivulus amambaiensis Volcan, Severo-Neto & Lanés, 2018 Melanorivulus apiamici (W. J. E. M. Costa, 1989) Melanorivulus atlanticus W. J. E. M. Costa, Bragança & Ottoni, 2015 Melanorivulus bororo (W. J. E. M. Costa, 2008) Melanorivulus britzkei Nielsen, 2017 Melanorivulus canesi Nielsen, 2017 Melanorivulus crixas (W. J. E. M. Costa, 2007) Melanorivulus cyanopterus (W. J. E. M. Costa, 2005) Melanorivulus dapazi (W. J. E. M. Costa, 2005) Melanorivulus decoratus (W. J. E. M. Costa, 1989) Melanorivulus egens (W. J. E. M. Costa, 2005) Melanorivulus faucireticulatus (W. J. E. M. Costa, 2008) Melanorivulus flavipinnis W. J. E. M. Costa, 2017 Melanorivulus formosensis (W. J. E. M. Costa, 2008) Melanorivulus giarettai (W. J. E. M. Costa, 2008) Melanorivulus ignescens W. J. E. M. Costa, 2017 Melanorivulus illuminatus (W. J. E. M. Costa, 2007) Melanorivulus imperatrizensis D. T. B. Nielsen & C. S. Pinto, 2015 Melanorivulus interruptus Volcan, Severo-Neto & Lanés, 2018 Melanorivulus ivinhemensis Volcan, Severo-Neto & Lanés, 2018 Melanorivulus jalapensis (W. J. E. M. Costa, 2010) Melanorivulus javahe (W. J. E. M. Costa, 2007) Melanorivulus karaja (W. J. E. M. Costa, 2007) Melanorivulus kayabi (W. J. E. M. Costa, 2008) Melanorivulus kayapo (W. J. E. M. Costa, 2006) Melanorivulus kunzei W. J. E. M. Costa, 2012 Melanorivulus leali W. J. E. M. Costa, 2013 Melanorivulus linearis W. J. E. M. Costa, 2018 Melanorivulus litteratus (W. J. E. M. Costa, 2005) Melanorivulus megaroni (W. J. E. M. Costa, 2010) Melanorivulus melanopterus Nielsen & Ohara, 2024 Melanorivulus modestus (W. J. E. M. Costa, 1991) Melanorivulus nelsoni Volcan, Severo-Neto & Lanés, 2017 Melanorivulus nigromarginatus W. J. E. M. Costa, 2018 Melanorivulus nigropunctatus Volcan, Klotzel & Lanés, 2017 Melanorivulus ofaie Volcan, Klotzel & Lanés, 2017 Melanorivulus paracatuensis (W. J. E. M. Costa, 2003) Melanorivulus paresi (W. J. E. M. Costa, 2008) Melanorivulus parnaibensis (W. J. E. M. Costa, 2003) Melanorivulus petrisecundi W. J. E. M. Costa, 2016 Melanorivulus pictus (W. J. E. M. Costa, 1989) Melanorivulus pindorama W. J. E. M. Costa, 2012 Melanorivulus pinima (W. J. E. M. Costa, 1989) Melanorivulus planaltinus (W. J. E. M. Costa & Brasil, 2008) Melanorivulus polychromus D. T. B. Nielsen, P. A. B. A. Neves, Ywamoto & Passos, 2016 Melanorivulus proximus W. J. E. M. Costa, 2018 Melanorivulus punctatus (Boulenger, 1895) Melanorivulus regularis W. J. E. M. Costa, 2017 Melanorivulus rossoi (W. J. E. M. Costa, 2005) Melanorivulus rubromarginatus (W. J. E. M. Costa, 2007) Melanorivulus rubroreticulatus W. J. E. M. Costa, Amorim & Bragança, 2014 Melanorivulus rutilicaudus (W. J. E. M. Costa, 2005) Melanorivulus salmonicaudus (W. J. E. M. Costa, 2007) Melanorivulus scalaris (W. J. E. M. Costa, 2005) Melanorivulus schuncki (W. J. E. M. Costa & de Luca, 2011) Melanorivulus spixi W. J. E. M. Costa, 2016 Melanorivulus terena Volcan, Severo-Neto & Lanés, 2024 Melanorivulus ubirajarai W. J. E. M. Costa, 2012 Melanorivulus violaceus (W. J. E. M. Costa, 1991) Melanorivulus vittatus (W. J. E. M. Costa, 1989) Melanorivulus wallacei W. J. E. M. Costa, 2016 Melanorivulus zygonectes (G. S. Myers, 1927)
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