The toros or brush-tailed rats, genus ''Isothrix'', are a group of spiny rats found in

tropical The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in the Southern Hemisphere at S. The tropics are also referred to ...

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 souther ...

, particularly in the

Amazon Basin The Amazon basin is the part of South America drained by the Amazon River and its tributaries. The Amazon drainage basin covers an area of about , or about 35.5 percent of the South American continent. It is located in the countries of Boli ...

.Nowak, Ronald M. 1999. ''Walker's Mammals of the World'', 6th edition. Johns Hopkins University Press, 1936 pp.

Description

Toros look like large rats with soft fur on the body and long

guard hair Guard hair or overhair is the outer layer of hair of most mammals, which overlay the fur. Guard hairs are long and coarse and protect the rest of the pelage (fur) from abrasion and frequently from moisture. They are visible on the surface of the fu ...

s on the scaly tail.Emmons, L.H. 2005. A Revision of the Genera of Arboreal Echimyidae (Rodentia: Echimyidae, Echimyinae), With Descriptions of Two New Genera. pp. 247–310 in Lacey, E.A. & Myers, P. 2005. Mammalian Diversification: From Chromosomes to Phylogeography (A Celebration of the Career of James L. Patton). University of California Publications in Zoology. Head and body is 18-27.5 cm and tail is 17–30 cm. Weight is 320-570 grams.

Natural history

These animals appear to be

arboreal Arboreal locomotion is the locomotion of animals in trees. In habitats in which trees are present, animals have evolved to move in them. Some animals may scale trees only occasionally, but others are exclusively arboreal. The habitats pose num ...

, based on the shape of their hind feet. They are thought to spend the day in holes in the ground near trees.

Systematics

The etymology of the genus name ''Isothrix'' corresponds to the two

ancient greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic p ...

words (), meaning "of equal length", and , (), meaning "hair". The etymology of the genus name

synonym A synonym is a word, morpheme, or phrase that means exactly or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are al ...

''Lasiuromys'' corresponds to the three

words (), meaning "furry, with tufted hair", (), meaning "animal tail", and (), meaning "mouse, rat". There are currently five

species In biology, a species is the basic unit of Taxonomy (biology), 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 ...

recognized in the

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

''Isothrix'': * ''

Isothrix barbarabrownae ''Isothrix barbarabrownae'' is a recently discovered species of rodents of the spiny rat family Echimyidae. Discovery It was discovered in Peru, and is about the same size as a large squirrel, such as a Eurasian red squirrel. It is brown, wit ...

''- Barbara Brown's Brush-tailed Rat * ''

Isothrix bistriata The yellow-crowned brush-tailed rat (''Isothrix bistriata'') is a South American species of brush-tailed rat in the family Echimyidae. It is found in Bolivia, Brazil, Colombia, Ecuador, Peru, and Venezuela. They are nocturnal and arboreal anima ...

'' - Yellow-crowned brush-tailed rat * ''

Isothrix negrensis The Rio Negro brush-tailed rat or dark brush-tailed tree rat (''Isothrix negrensis''), is a spiny rat species found in Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in b ...

'' - Rio Negro brush-tailed rat * ''

Isothrix pagurus The Plain brush-tailed rat (''Isothrix pagurus'') is a spiny rat species found in Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America ...

'' - Plain brush-tailed rat * ''

Isothrix sinnamariensis The Sinnamary brush-tailed rat (''Isothrix sinnamariensis''), is a species of rodent in the family Echimyidae. It is found in French Guiana, Guyana, and possibly Suriname Suriname (; srn, Sranankondre or ), officially the Republic of Suri ...

'' - Sinnamary brush-tailed rat There does appear to be good support for the

monophyly In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic gr ...

of three species found in this genus.

Phylogeny

''Isothrix'' is a member of the Echimyini clade of

Echimyidae rodents. Although tentatively considered an echimyine, it has been suggested that ''Isothrix'' may not be particularly closely related to other members of its subfamily. This is confirmed by molecular phylogenies in which ''Isothrix'' appears as a distant relative of the three clades of Echimyini: (i) ''Echimys'', ''Phyllomys'', ''Makalata'', ''Pattonomys'', and ''Toromys'' ; (ii) the bamboo rats ''Dactylomys'', ''Olallamys'', ''Kannabateomys'' together with ''Diplomys'' and ''Santamartamys'' ; and (iii) the arboreal eumysopines ''Mesomys'' and ''Lonchothrix''. The taxon ''

Callistomys pictus The painted tree-rat (''Callistomys pictus'') is a species of spiny rat from Brazil, restricted to north-eastern Bahia in eastern Brazil. It is the only species in the genus ''Callistomys''. Identification With a total length of ca. 30 cm ...

'' was previously member of the genus ''Isothrix'', but most authors considered it distinct enough to warrant a separate genus. This distinctness has been confirmed by DNA comparative studies in which ''Callistomys'' even appears to branch with members of a distinct tribe (i.e., Myocastorini) of the subfamily Echimyinae. The arboreal genera of the subfamily Echimyinae therefore constitute a

polyphyletic A polyphyletic group is an assemblage of organisms or other evolving elements that is of mixed evolutionary origin. The term is often applied to groups that share similar features known as homoplasies, which are explained as a result of conver ...

assemblage.

References

{{Taxonbar, from=Q911355 Rodent genera Taxa named by Johann Andreas Wagner