Oligoryzomys nigripes, also known as the Black-footed Colilargo or the Black-footed Pygmy Rice Rat, is a rodent

Rodent

Rodentia is an order of mammals also known as rodents, characterised by two continuously growing incisors in the upper and lower jaws which must be kept short by gnawing....

 in the genus Oligoryzomys

Oligoryzomys

Oligoryzomys is a genus of rodents in the tribe Oryzomyini of family Cricetidae. Many species are known as pygmy rice rats or colilargos...

of family Cricetidae

Cricetidae

The Cricetidae are a family of rodents in the large and complex superfamily Muroidea. It includes true hamsters, voles, lemmings, and New World rats and mice...

. It is found from Pernambuco

Pernambuco

Pernambuco is a state of Brazil, located in the Northeast region of the country. To the north are the states of Paraíba and Ceará, to the west is Piauí, to the south are Alagoas and Bahia, and to the east is the Atlantic Ocean. There are about of beaches, some of the most beautiful in the...

 in northeastern Brazil through the Atlantic Forest and Cerrado

Cerrado

The Cerrado, is a vast tropical savanna ecoregion of Brazil, particularly in the states of Gioas and Minas Gerais...

 into Paraguay, Uruguay, and Argentina, where it occurs in the provinces of Chaco

Chaco Province

Chaco is an Argentine province located in the north of the country, near the border with Paraguay. Its capital is Resistencia on the Paraná River opposite the city of Corrientes...

, Misiones

Misiones Province

Misiones is one of the 23 provinces of Argentina, located in the northeastern corner of the country in the Mesopotamiсa region. It is surrounded by Paraguay to the northwest, Brazil to the north, east and south, and Corrientes Province of Argentina to the southwest.- History :The province was...

, and Buenos Aires

Buenos Aires Province

The Province of Buenos Aires is the largest and most populous province of Argentina. It takes the name from the city of Buenos Aires, which used to be the provincial capital until it was federalized in 1880...

. Two other species, Oligoryzomys delticola (also known as the Delta Pygmy Rice Rat or the Large Colilargo) and Oligoryzomys eliurus (also known as the Brazilian Pygmy Rice Rat or the Brazilian Colilargo) have been recognized as synonyms

Synonym (taxonomy)

In scientific nomenclature, a synonym is a scientific name that is or was used for a taxon of organisms that also goes by a different scientific name. For example, Linnaeus was the first to give a scientific name to the Norway spruce, which he called Pinus abies...

 of O. nigripes since 2005; they cannot be distinguished on the basis of morphology

Morphology (biology)

In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....

, karyotype

Karyotype

A karyotype is the number and appearance of chromosomes in the nucleus of an eukaryotic cell. The term is also used for the complete set of chromosomes in a species, or an individual organism.p28...

, or morphometrics

Morphometrics

Morphometrics refers to the quantitative analysis of form, a concept that encompasses size and shape. Morphometric analyses are commonly performed on organisms, and are useful in analyzing their fossil record, the impact of mutations on shape, developmental changes in form, covariances between...

. It is a large species with long ears, dark yellow to dark brown upperparts, sharply delimited from the whitish underparts, and often a pink girdle on the chest. The karyotype

Karyotype

A karyotype is the number and appearance of chromosomes in the nucleus of an eukaryotic cell. The term is also used for the complete set of chromosomes in a species, or an individual organism.p28...

is 2n = 62, FNa = 78–82.

Literature cited

• Leite, Y. and Patterson, B. 2008. . In IUCN. IUCN Red List of Threatened Species. Version 2009.2. <www.iucnredlist.org>. Downloaded on November 28, 2009.
• Musser, G.G. and Carleton, M.D. 2005. Superfamily Muroidea. Pp. 894–1531 in Wilson, D.E. and Reeder, D.M. (eds.). Mammal Species of the World: a taxonomic and geographic reference. 3rd ed. Baltimore: The Johns Hopkins University Press, 2 vols., 2142 pp. ISBN 978-0-8018-8221-0
• Pardinas, U. and D'Elia, G. 2008. . In IUCN. IUCN Red List of Threatened Species. Version 2009.2. <www.iucnredlist.org>. Downloaded on November 28, 2009.
• Weksler, M. & Bonvicino, C.R. 2005. Taxonomy of pygmy rice rats genus Oligoryzomys Bangs, 1900 (Rodentia, Sigmodontinae) of the Brazilian Cerrado, with the description of two new species. Arquivos do Museu Nacional 63(1):113–130.
• Weksler, M., Bonvicino, C., D'Elia, G. and Teta, P. 2008. . In IUCN. IUCN Red List of Threatened Species. Version 2009.2. <www.iucnredlist.org>. Downloaded on November 28, 2009.