The rodent subfamily Sigmodontinae includes New World rats and mice, with at least 376 species. Many authorities include the Neotominae and Tylomyinae as part of a larger definition of Sigmodontinae. When those genera are included, the species count numbers at least 508. Their distribution includes much of the New World, but the genera are predominantly South American, such as brucies. They invaded South America from Central America as part of the Great American Interchange near the end of the Miocene, about 5 million years ago. Sigmodontines proceeded to diversify explosively in the formerly isolated continent. They inhabit many of the same ecological niches that the Murinae occupy in the Old World.
Akodon is a genus consisting of South American grass mice. They mostly occur south of the Amazon Basin and along the Andes north to Venezuela, but are absent from much of the basin itself, the far south of the continent, and the lowlands west of the Andes. Akodon is one of the most species-rich genera of Neotropical rodents. Species of Akodon are known to inhabit a variety of habitats from tropical and tropical moist forests to altiplano and desert. Fossils are known from the late Pliocene onwards.
Bibimys is a genus of new world rats. Commonly known as the crimson-nosed rats, there are three species:
Cuvier's spiny-rat is a spiny rat species found in Brazil, French Guiana, Guyana, Peru and Suriname.
Gardner's spiny-rat is a spiny rat species found in Bolivia and Brazil.
Goeldi's spiny-rat is a spiny rat species found in Brazil.
The Napo spiny rat is a spiny rat species found in Brazil, Colombia, Ecuador, Peru and Venezuela.
Simons's spiny rat is a spiny rat species found in Bolivia, Brazil, Colombia, Ecuador and Peru. It was named for American scientific collector Perry O. Simons.
Oligoryzomys flavescens, also known as the flavescent colilargo or yellow pygmy rice rat is a species of rodent in the genus Oligoryzomys of family Cricetidae. It is found in southern South America, occurring in southern Brazil, Paraguay, Uruguay, and northeastern Argentina. Its karyotype has 2n = 64-66 and FNa = 66–70.
The Caparaó hocicudo is a rodent species from South America. It is endemic to Brazil where it is found in the Pico da Bandeira mountain range.
Brucepattersonius griserufescens, also known as the gray-bellied akodont or grey-bellied brucie, is a rodent in the cricetid genus Brucepattersonius from southeastern Brazil, specifically the states of Minas Gerais, Espírito Santo and Rio de Janeiro between 1,300 and 2,700 metres. It was one of four species of Brucepattersonius described by Hershkovitz in 1998; another, Brucepattersonius albinasus, also known as the white-nosed akodont or white-nosed brucie, was later argued to be the same as B. griserufescens, though further work is needed to confirm this. It is threatened by habitat loss but is also protected by Caparaó National Park.
Akodon spegazzinii, also known as Spegazzini's akodont or Spegazzini's grass mouse, is a rodent in the genus Akodon found in northwestern Argentina. It occurs in grassland and forest at 400 to 3,500 m above sea level. After the species was first named in 1897, several other names were given to various populations now included in A. spegazzinii. They are now all recognized as part of a single, widespread and variable species. Akodon spegazzinii is related to Akodon boliviensis and other members of the A. boliviensis species group. It reproduces year-round. Because it is widely distributed and common, Akodon spegazzinii is listed as "least concern" on the IUCN Red List.
Oligoryzomys destructor, also known as Tschudi's colilargo or the destructive pygmy rice rat, is a species of rodent in the genus Oligoryzomys of family Cricetidae. It is found along the eastern Andes from southern Colombia, through Ecuador, Peru, and Bolivia into northern Argentina. Its karyotype has 2n = 60 and FNa = 76.
Oligoryzomys magellanicus, also known as the Patagonian colilargo and the Magellanic pygmy rice rat, is a species of rodent in the genus Oligoryzomys of the family Cricetidae. It is found in the southernmost parts of Argentina and Chile, including Tierra del Fuego and other outlying islands. Its karyotype has 2n = 54 and FNa = 66.
The Pacific spiny rat is a species of rodent in the family Echimyidae. It is found in Ecuador and Peru.
O'Connell's spiny-rat is a species of rodent in the family Echimyidae. It is endemic to Colombia.
Anita's leaf-eared mouse is a species of rodent in the family Cricetidae. It was discovered in Tucumán Province in northwestern Argentina in alder forest of the upper part of the Southern Andean Yungas ecoregion, on the eastern slopes of the Andes. The species is terrestrial and nocturnal, and was named after American zoologist Anita K. Pearson. It appears to be most closely related to the bunchgrass leaf-eared mouse.
The delicate salt flat mouse is a sigmodontine rodent species in the family Cricetidae from South America. It is the only species in the genus Salinomys. Its habitat is scrublands bordering salt flats in the Monte Desert area of central western Argentina at elevations around 400 m. The closest relatives of the species are the chaco mice (Andalgalomys).
The ravine hocicudo is a rodent species from South America. It is found in Argentina.
Calassomys apicalis is the only species of the genus Calassomys, a rodent in the family Cricetidae. It lives in the east of South America.
