The Montecristo cichlid (''Oscura heterospila'') is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

of freshwater fish from the Atlantic slope of southern

Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...

and

Guatemala Guatemala ( ; ), officially the Republic of Guatemala ( es, República de Guatemala, links=no), is a country in Central America. It is bordered to the north and west by Mexico; to the northeast by Belize and the Caribbean; to the east by H ...

. This

cichlid Cichlids are fish from the family Cichlidae in the order Cichliformes. Cichlids were traditionally classed in a suborder, the Labroidei, along with the wrasses ( Labridae), in the order Perciformes, but molecular studies have contradicted this ...

occurs in lagoons, creeks and rivers with slight to moderate current in the Grijalva–

Usumacinta The Usumacinta River (; named after the howler monkey) is a river in southeastern Mexico and northwestern Guatemala. It is formed by the junction of the Pasión River, which arises in the Sierra de Santa Cruz (in Guatemala) and the Salinas R ...

, Candelaria, Champotón and

Coatzacoalcos Coatzacoalcos () is a major port city in the southern part of the Mexican state of Veracruz, mostly on the western side of the Coatzacoalcos River estuary, on the Bay of Campeche, on the southern Gulf of Mexico coast. The city serves as the munic ...

river drainages. It is currently recognized as the only species in its

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

, but it is closely related to –and possibly should be merged into– ''

Vieja ''Vieja'' is a genus of cichlid fish from Central America and Mexico. The majority of the species are freshwater fish found in stagnant or slow-moving waters of southern Mexico to El Salvador, but ''V. maculicauda'', which also occurs in brack ...

'' (a genus where it also has been placed in the past). The Montecristo cichlid reaches up to in

standard 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 m ...

References

Heroini Fish described in 1936 {{Cichlidae-stub