Toros look like largerats with soft fur on the body and longguard hairs on the scaly tail.[3] Head and body is 18-27.5 cm and tail is 17–30 cm.[2] Weight is 320-570 grams.
The etymology of the genus nameIsothrix corresponds to the twoancient greek wordsἴσος (ísos), meaning "of equal length", andθρίξ,τριχός (thríx, trikhós), meaning "hair".[4][5] The etymology of the genus namesynonymLasiuromys corresponds to the threeancient greek wordsλάσιος (lásios), meaning "furry, with tufted hair",οὐρά (ourá), meaning "animal tail", andμῦς (mûs), meaning "mouse, rat".[4][5]
There are currently fivespecies recognized in thegenusIsothrix:[6]
Isothrix is a member of theEchimyini clade ofarboreal Echimyidae rodents.[8] Although tentatively considered anechimyine, it has been suggested thatIsothrix may not be particularly closely related to other members of its subfamily.[3] This is confirmed by molecular phylogenies in whichIsothrix appears as a distant relative of the three clades ofEchimyini: (i)Echimys,Phyllomys,Makalata,Pattonomys, andToromys ; (ii) the bamboo ratsDactylomys,Olallamys,Kannabateomys together withDiplomys andSantamartamys ; and (iii) the arboreal eumysopinesMesomys andLonchothrix.[9]
The taxonCallistomys pictus was previously member of the genusIsothrix, but most authors considered it distinct enough to warrant a separate genus.[10] This distinctness has been confirmed by DNA comparative studies in whichCallistomys even appears to branch with members of a distinct tribe (i.e.,Myocastorini) of the subfamily Echimyinae.[11][8][9] The arboreal genera of the subfamily Echimyinae therefore constitute apolyphyletic assemblage.
^abcNowak, Ronald M. 1999.Walker's Mammals of the World, 6th edition. Johns Hopkins University Press, 1936 pp. ISBN0-8018-5789-9
^abcEmmons, 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.
^Lara, Márcia C.;Patton, James L.; da Silva, Maria Nazareth F. (1996). "The Simultaneous Diversification of South American Echimyid Rodents (Hystricognathi) Based on Complete Cytochromeb Sequences".Molecular Phylogenetics and Evolution.5 (2):403–413.Bibcode:1996MolPE...5..403L.doi:10.1006/mpev.1996.0035.PMID8728398.
^Galewski, Thomas; Mauffrey, Jean-François; Leite, Yuri L. R.; Patton, James L.; Douzery, Emmanuel J. P. (2005). "Ecomorphological diversification among South American spiny rats (Rodentia; Echimyidae): a phylogenetic and chronological approach".Molecular Phylogenetics and Evolution.34 (3):601–615.Bibcode:2005MolPE..34..601G.doi:10.1016/j.ympev.2004.11.015.PMID15683932.
^Upham, Nathan S.; Patterson, Bruce D. (2012). "Diversification and biogeography of the Neotropical caviomorph lineage Octodontoidea (Rodentia: Hystricognathi)".Molecular Phylogenetics and Evolution.63 (2):417–429.Bibcode:2012MolPE..63..417U.doi:10.1016/j.ympev.2012.01.020.PMID22327013.
^Fabre, Pierre-Henri; Galewski, Thomas; Tilak, Marie-ka; Douzery, Emmanuel J. P. (2013-03-01). "Diversification of South American spiny rats (Echimyidae): a multigene phylogenetic approach".Zoologica Scripta.42 (2):117–134.doi:10.1111/j.1463-6409.2012.00572.x.ISSN1463-6409.
^Upham, Nathan S.; Patterson, Bruce D. (2015). "Evolution of Caviomorph rodents: a complete phylogeny and timetree for living genera". In Vassallo, Aldo Ivan; Antenucci, Daniel (eds.).Biology of caviomorph rodents: diversity and evolution. Buenos Aires: SAREM Series A, Mammalogical Research — Sociedad Argentina para el Estudio de los Mamíferos. pp. 63–120.
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