''Nephelomys levipes'', also known as the nimble-footed oryzomysMusser and Carleton, 2005, p. 1150 or light-footed rice rat, is a species of

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 n ...

in the genus '' Nephelomys'' of 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 h ...

.Weksler et al., 2006, p. 18 It is found on the eastern slope 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 ...

from southeastern

Peru , image_flag = Flag of Peru.svg , image_coat = Escudo nacional del Perú.svg , other_symbol = Great Seal of the State , other_symbol_type = National seal , national_motto = "Firm and Happy f ...

into west-central Bolivia in cloud forest at elevations from . It occurs in the same general area as its congener '' N. keaysi'', but at higher altitudes. In 1902, Oldfield Thomas first described this species, under the name ''Oryzomys levipes'', on the basis of specimens from both Peru and Bolivia. He compared it to the previously described ''O. keaysi'', the current ''Nephelomys keaysi'', of which he considered it to be a "smaller form".Thomas, 1902, p. 129 In 1944, Philip Hershkovitz relegated both ''O. levipes'' and ''O. keaysi'' to the

synonymy 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 all ...

of '' O. albigularis'', where it remained until it was reinstated a species in the early 1990s on the basis of genetic and other differences. When ''O. albigularis'' and related species were reclassified into a new genus, ''Nephelomys'', in 2006, it was retained as a separate species, but under the name of ''Nephelomys levipes''. It is similar to ''N. keaysi'', but smaller, and the fur on the underparts is buffy instead of whitish in the specimens Thomas examined. The

interorbital region The interorbital region of the skull is located between the eyes, anterior to the braincase. The form of the interorbital region may exhibit significant variation between taxonomic groups. In oryzomyine rodents, for example, the width, form, an ...

of the skull is narrow. The

incisive foramina In the human mouth, the incisive foramen (also known as: "''anterior palatine foramen''", or "''nasopalatine foramen''") is the opening of the incisive canals on the hard palate immediately behind the incisor teeth. It gives passage to blood vesse ...

, which perforate the

palate The palate () is the roof of the mouth in humans and other mammals. It separates the oral cavity from the nasal cavity. A similar structure is found in crocodilians, but in most other tetrapods, the oral and nasal cavities are not truly separ ...

between the

incisor Incisors (from Latin ''incidere'', "to cut") are the front teeth present in most mammals. They are located in the premaxilla above and on the mandible below. Humans have a total of eight (two on each side, top and bottom). Opossums have 18, wher ...

s and the

molars The molars or molar teeth are large, flat teeth at the back of the mouth. They are more developed in mammals. They are used primarily to grind food during chewing. The name ''molar'' derives from Latin, ''molaris dens'', meaning "millstone to ...

, are long and narrow. The bony palate is short, with its posterior end often located between the third molars. The alisphenoid strut, an extension of the

alisphenoid The greater wing of the sphenoid bone, or alisphenoid, is a bony process of the sphenoid bone; there is one on each side, extending from the side of the body of the sphenoid and curving upward, laterally, and backward. Structure The greater wi ...

bone of the skull that separates two

foramina In anatomy and osteology, a foramen (;Entry "foramen"
in

(openings) in the skull, is present in some individuals. The

mastoid The mastoid part of the temporal bone is the posterior (back) part of the temporal bone, one of the bones of the skull. Its rough surface gives attachment to various muscles (via tendons) and it has openings for blood vessels. From its borders, ...

bone usually contains some openings.Weksler et al., 2006, p. 19 In the

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of sever ...

, the head and body length is 130 mm, the tail length is 160 mm, the hindfoot length (without claws) is 31 mm, the ear length is 27 mm, and the skull length is 35.7 mm.

References

Literature cited

* Hershkovitz, P. 1944. A systematic review of the Neotropical water rats of the genus ''Nectomys'' (Cricetinae). Miscellaneous Publications Museum of Zoology, University of Michigan 58: 1–88. * * Thomas, O. 1901. New mammals from Peru and Bolivia, with a list of those collected from the Inambari River, Upper Madre de Dios. Annals and Magazine of Natural History (7)7:178–190. * * Zeballos, H., Vargas, J. and Weksler, M. 2008. . In IUCN. 2008 IUCN Red List of Threatened Species. Retrieved on April 24, 2009. {{Taxonbar, from=Q1767494 Mammals of Bolivia Mammals of Peru Nephelomys Mammals described in 1902 Taxa named by Oldfield Thomas Taxonomy articles created by Polbot