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, where the sun may shine directly overhead. This contrasts with the temperate or polar regions of Earth, where the Sun can never be directly overhead. This is because of Earth's ax ...

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...

, particularly in the

Amazon Basin The Amazon basin is the part of South America drained by the Amazon River and its tributary, 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 ...

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

Description

Toros look like large

rat Rats are various medium-sized, long-tailed rodents. Species of rats are found throughout the order Rodentia, but stereotypical rats are found in the genus ''Rattus''. Other rat genera include '' Neotoma'' (pack rats), '' Bandicota'' (bandicoo ...

s 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 ...

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 (scansorial), but others are exclusively arboreal. The hab ...

, 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 classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...

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 precisely 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 a ...

''Lasiuromys'' corresponds to the three

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

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

recognized in the

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

''Isothrix'': * '' Isothrix barbarabrownae''- Barbara Brown's Brush-tailed Rat * '' Isothrix bistriata'' - Yellow-crowned brush-tailed rat * '' Isothrix negrensis'' - Rio Negro brush-tailed rat * '' Isothrix pagurus'' - Plain brush-tailed rat * '' Isothrix sinnamariensis'' - Sinnamary brush-tailed rat There does appear to be good support for the

monophyly In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent comm ...

of three species found in this genus.

Phylogeny

''Isothrix'' is a member of the

Echimyini Echimyini is a tribe of echimyid rodents, proposed in 2016, and containing 13 extant genera: all of the tree rats '' Echimys'', ''Phyllomys'', '' Makalata'', '' Pattonomys'', '' Toromys'', '' Diplomys'', '' Santamartamys'', and '' Isothrix'', the ...

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

: (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'' 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 Myocastorini is a tribe of echimyid rodents, proposed in 2017, and containing the five extant genera '' Callistomys'', '' Hoplomys'', '' Myocastor'', ''Proechimys ''Proechimys'' is a genus of South American South America is a contine ...

) of the subfamily Echimyinae. The arboreal genera of the subfamily Echimyinae therefore constitute a

polyphyletic A polyphyletic group is an assemblage that includes organisms with mixed evolutionary origin but does not include their most recent common ancestor. The term is often applied to groups that share similar features known as Homoplasy, homoplasies ...

assemblage.

References

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