''Melanorivulus'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

of South American

freshwater fish Freshwater fish are those that spend some or all of their lives in fresh water, such as rivers and lakes, with a salinity of less than 1.05%. These environments differ from marine conditions in many ways, especially the difference in levels of ...

in the

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

Rivulidae The Rivulidae are a family of killifishes in the order Cyprinodontiformes. They are commonly known as rivulids, South American killifish or New World killifish. The latter names are slightly misleading, however, as they are neither restricted to ...

. Most species are

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found else ...

to the

Río de la Plata The Río de la Plata (, "river of silver"), also called the River Plate or La Plata River in English, is the estuary formed by the confluence of the Uruguay River and the Paraná River at Punta Gorda. It empties into the Atlantic Ocean and fo ...

, eastern

Amazon Amazon most often refers to: * Amazons, a tribe of female warriors in Greek mythology * Amazon rainforest, a rainforest covering most of the Amazon basin * Amazon River, in South America * Amazon (company), an American multinational technolog ...

(west to

Tapajós The Tapajós ( pt, Rio Tapajós ) is a river in Brazil. It runs through the Amazon Rainforest and is a major tributary of the Amazon River. When combined with the Juruena River, the Tapajós is approximately long. It is one of the largest clearw ...

basin),

Tocantins Tocantins () is one of the 26 states of Brazil. It is the newest state, formed in 1988 and encompassing what had formerly been the northern two-fifths of the state of Goiás. Tocantins covers and had an estimated population of 1,496,880 in 20 ...

– 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 Parnaíba () is a city in the Brazilian state of Piauí. Having a population of over 150,000 inhabitants according to IBGE's 2020 report, it is the second most populous city in the state, after the capital Teresina. It is one of the four coastal ...

and

Sergipe Sergipe (), officially State of Sergipe, is a state of Brazil. Located in the Northeast Region along the Atlantic coast of the country, Sergipe is the smallest state in Brazil by geographical area at , larger only than the Federal District. Serg ...

in northeastern Brazil. Only ''M. schuncki'' occurs north of the Amazon River.Costa, W.J.E.M., Bragança, P.H.N. & Ottoni, F.P. (2015)
A new miniature killifish of the genus ''Melanorivulus'' (Cyprinodontiformes: Rivulidae) from the coastal plains of north-eastern Brazil.
''Vertebrate Zoology, 65 (1): 31–35.'' They inhabit shallow waters, generally deep, at the margins of streams in open or fairly open habitats like the

Cerrado The ''Cerrado'' (, ) is a vast ecoregion of tropical savanna in eastern Brazil, particularly in the states of Goiás, Mato Grosso do Sul, Mato Grosso, Tocantins, Minas Gerais, and the Federal District. The core areas of the Cerrado biome are the ...

or Cerrado–Amazon transition. Many have tiny ranges and are seriously

threatened Threatened species are any species (including animals, plants and fungi) which are vulnerable to endangerment in the near future. Species that are threatened are sometimes characterised by the population dynamics measure of ''critical depensa ...

.Costa, W.J.E.M. (2012)
Two new species of ''Melanorivulus'' from the Caiapós hill, upper Araguaia river basin, Brazil (Cyprinodontiformes: Rivulidae).
''Ichthyological Exploration of Freshwaters, 23 (3): 211-218.'' Similar to closely related genera such as ''

Anablepsoides ''Anablepsoides'' is a genus of killifish in the family Rivulidae native to tropical South America and the Lesser Antilles. The majority are from the Amazon and Orinoco basins, as well as freshwater systems in the Guiana Shield, but a few speci ...

'', ''

Atlantirivulus ''Atlantirivulus'' is a genus of fishes in the family Rivulidae. They are endemic to shallow swamps, creeks, streams and pools in the Atlantic Forest in southeastern Brazil, ranging from Rio de Janeiro to Santa Catarina.Costa, W.J.E.M. (2014)Fo ...

'', ''

Cynodonichthys ''Cynodonichthys'' is a genus of freshwater killifish in the family Rivulidae. They are found in Middle America, ranging from southern Mexico (north to Oaxaca and the Yucatán Peninsula), through Central America (where most species live), to Co ...

'' and '' Laimosemion'', ''Melanorivulus'' are jumpers and non-annual

killifish A killifish is any of various oviparous (egg-laying) cyprinodontiform fish (including families Aplocheilidae, Cyprinodontidae, Fundulidae, Profundulidae and Valenciidae). All together, there are 1,270 species of killifish, the biggest family ...

. ''Melanorivulus'' are small fish, with the largest species up in

total length Fish measurement is the measuring of individual fish and various parts of their anatomies. These data are used in many areas of ichthyology, including taxonomy and fisheries biology. Overall length * Standard length (SL) is the length of a fish ...

and the smallest less than . They are often quite colorful and some are kept in aquariums.

Species

Until 2011, ''Melanorivulus'' were included in ''

Rivulus ''Rivulus'' is a genus of small freshwater fish in the Cyprinodontiformes family Rivulidae. It was traditionally considered to be the largest genus in its family; however, the genus's size is currently in dispute. Wilson J. E. Costa split this ge ...

Brasil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area an ...

References

{{Taxonbar, from=Q6811535 Rivulidae Fish of South America Freshwater fish genera