''Rhagomys'' is a genus of

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the southe ...

rodent Rodents (from Latin , 'to gnaw') are mammals of the order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents. They are na ...

s in the tribe Thomasomyini of the family

Cricetidae The Cricetidae are a family of rodents in the large and complex superfamily Muroidea. It includes true hamsters, voles, lemmings, muskrats, and New World rats and mice. At almost 608 species, it is the second-largest family of mammals, and has m ...

. Two species separated by about 3100 km are known, from southeast

Peru , image_flag = Flag of Peru.svg , image_coat = Escudo nacional del Perú.svg , other_symbol = Great Seal of the State , other_symbol_type = Seal (emblem), National seal , national_motto = "Fi ...

and

Bolivia , image_flag = Bandera de Bolivia (Estado).svg , flag_alt = Horizontal tricolor (red, yellow, and green from top to bottom) with the coat of arms of Bolivia in the center , flag_alt2 = 7 × 7 square p ...

east of the

Andes The Andes, Andes Mountains or Andean Mountains (; ) are the longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range is long, wide (widest between 18°S – 20°S ...

, and in the

Atlantic Forest The Atlantic Forest ( pt, Mata Atlântica) is a South American forest that extends along the Atlantic coast of Brazil from Rio Grande do Norte state in the northeast to Rio Grande do Sul state in the south and inland as far as Paraguay and th ...

of southeast

Brazil 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 undetermined species of ''Rhagomys'' has also been reported from

Mato Grosso Mato Grosso ( – lit. "Thick Bush") is one of the states of Brazil, the third largest by area, located in the Central-West region. The state has 1.66% of the Brazilian population and is responsible for 1.9% of the Brazilian GDP. Neighboring ...

in central Brazil. The species are as follows: * Long-tongued arboreal mouse (''Rhagomys longilingua'') * Brazilian arboreal mouse (''Rhagomys rufescens'') This genus is distinguished from other

sigmodontine 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 c ...

rodents by the presence of a

nail Nail or Nails may refer to: In biology * Nail (anatomy), toughened protective protein-keratin (known as alpha-keratin, also found in hair) at the end of an animal digit, such as fingernail * Nail (beak), a plate of hard horny tissue at the tip ...

on the

hallux Toes are the digits (fingers) of the foot of a tetrapod. Animal species such as cats that walk on their toes are described as being '' digitigrade''. Humans, and other animals that walk on the soles of their feet, are described as being '' pl ...

Nuclear DNA Nuclear DNA (nDNA), or nuclear deoxyribonucleic acid, is the DNA contained within each cell nucleus of a eukaryotic organism. It encodes for the majority of the genome in eukaryotes, with mitochondrial DNA and plastid DNA coding for the rest. It ...

sequence analysis has indicated that it is a sister taxon to ''

Thomasomys ''Thomasomys'' is a genus of rodent in the family Cricetidae, named after British zoologist Oldfield Thomas. Nuclear DNA sequence analysis has indicated that it is a sister taxon to '' Rhagomys''. It contains the following species: * Anderson' ...

''. The geographic distribution may reflect a formerly continuous distribution made disjunct by extinctions, or may reflect limited sampling of the intervening areas. While no other mammal taxa have a similar geographic distribution, a group of hylid frogs does. ''

Juscelinomys ''Juscelinomys'' is a genus of burrowing mice. The name is derived from Brazilian president Juscelino Kubitschek Juscelino Kubitschek de Oliveira (; 12 September 1902 – 22 August 1976), also known by his initials JK, was a prominent Bra ...

'' is an example of another sigmodontine rodent genus that also has a disjunct distribution. Some disjunct distributions have been attributed to fluctuations in forest coverage during the

Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological Epoch (geology), epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fina ...

, resulting from the climatic swings of the

ice age An ice age is a long period of reduction in the temperature of Earth's surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers. Earth's climate alternates between ice ages and gree ...

. However, the report of molars of an unknown member of the genus in an

ocelot The ocelot (''Leopardus pardalis'') is a medium-sized spotted wild cat that reaches at the shoulders and weighs between on average. It was first described by Carl Linnaeus in 1758. Two subspecies are recognized. It is native to the southwes ...

scat sample from a geographically intermediate location suggests that the disjunct distribution may well be artifact of limited sampling.

References

Rodent genera Taxa named by Oldfield Thomas {{Sigmodontinae-stub