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.
Philip Myers's akodont is a recently described species of grass mouse from Misiones Province, Argentina. Like other grass mice, A. philipmyersi is a small, non-descript, greyish-brown mouse with prominent ears. The species was recognized as distinct from other grass mice on the basis of unique features of karyology, genetic sequence, cranial measurements, and general morphology.
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.
Necromys is a genus of South American sigmodontine rodents allied to Akodon. This genus has also been known as Cabreramys or more recently Bolomys, and the northern grass mouse has recently been transferred from Akodon.
Akodon azarae, also known as Azara's akodont or Azara's grass mouse, is a rodent species from South America. It is found from southernmost Brazil through Paraguay and Uruguay into eastern Argentina. It is named after Spanish naturalist Félix de Azara.
The cursor grass mouse or cursorial akodont, is a sigmodontine rodent from South America.
The montane grass mouse is a rodent species from South America. It is found in Argentina, Brazil, Paraguay and Uruguay.
The Paraná grass mouse is a South American rodent species of the family Cricetidae. It is found in northeastern Argentina and southeastern Brazil.
The red hocicudo is a rodent species from South America. It is found in Argentina, Brazil and Uruguay.
Akodon albiventer, also known as the white-bellied grass mouse or white-bellied akodont, is a species of rodent in the family Cricetidae. It is found in the Andean highlands from southeastern Peru to southwestern Bolivia, northwestern Argentina, and far northeastern Chile at elevations from 2400 m to over 5000 m.
Akodon boliviensis, also known as the Bolivian grass mouse or Bolivian akodont, is a species of rodent in the family Cricetidae. It is found in the Andes from southeastern Peru through Bolivia into northwestern Argentina.
Akodon budini, also known as Budin's akodont or Budin's grass mouse, is a species of rodent in the family Cricetidae. It is found in the Andes of northwestern Argentina and adjacent Bolivia. The species is named after Emilio Budin, an Argentine specimen collector who worked with Oldfield Thomas.
The intelligent grass mouse or Patagonian akodont is a species of rodent in the family Cricetidae. It is found in Argentina and Chile.
Kemp's grass mouse is a species of South American rodent in the family Cricetidae. It is the only species in the genus Deltamys. It was formerly considered a member of the genus Akodon, but is now considered sufficiently distinct to warrant its own genus. It is named for Robin Kemp, who collected specimens of mice from the area for the British Museum.
Abrothrix lanosus, also known as the woolly grass mouse or woolly akodont, is a species of rodent in the family Cricetidae. It is found in southern Argentina and Chile. It was previously classified in the genus Akodon rather than Abrothrix.
Molina's grass mouse is a species of rodent in the family Cricetidae. It is found only in Argentina.
The Neuquén grass mouse is a species of rodent in the family Cricetidae. It is found only in Argentina. As of 2017, the IUCN synonymizes it with Akodon dolores.
The white-throated or grey-bellied grass mouse is a species of rodent in the family Cricetidae. It is found in Argentina and Bolivia.
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.
Akodon sylvanus, also known as the forest grass mouse or woodland akodont, is a species of rodent in the family Cricetidae. It is found only in a small part of northwestern Argentina.
