Light-Footed Rice Rat
Encyclopedia
Nephelomys levipes, also known as the Nimble-footed Oryzomys or Light-footed Rice Rat, is a species of rodent
in the genus Nephelomys
of family Cricetidae
. It is found on the eastern slope of the Andes
from southeastern Peru
into west-central Bolivia
in cloud forest
at elevations from 1800 to 3200 m (5,905.5 to 10,498.7 ft). 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". In 1944, Philip Hershkovitz
relegated both O. levipes and O. keaysi to the synonymy
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
of the skull is narrow. The incisive foramina
, which perforate the palate
between the incisor
s and the molars
, 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 bone of the skull that separates two foramina (openings) in the skull, is present in some individuals. The mastoid bone usually contains some openings. In the holotype
, 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.
Rodent
Rodentia is an order of mammals also known as rodents, characterised by two continuously growing incisors in the upper and lower jaws which must be kept short by gnawing....
in the genus Nephelomys
Nephelomys
Nephelomys is a genus of South American oryzomyine rodents found in the Andes from Bolivia to Venezuela, with a westward extension into the mountains of Costa Rica...
of family Cricetidae
Cricetidae
The Cricetidae are a family of rodents in the large and complex superfamily Muroidea. It includes true hamsters, voles, lemmings, and New World rats and mice...
. It is found on the eastern slope of the Andes
Andes
The Andes is the world's longest continental mountain range. It is a continual range of highlands along the western coast of South America. This range is about long, about to wide , and of an average height of about .Along its length, the Andes is split into several ranges, which are separated...
from southeastern Peru
Peru
Peru , officially the Republic of Peru , is a country in western South America. It is bordered on the north by Ecuador and Colombia, on the east by Brazil, on the southeast by Bolivia, on the south by Chile, and on the west by the Pacific Ocean....
into west-central Bolivia
Bolivia
Bolivia officially known as Plurinational State of Bolivia , is a landlocked country in central South America. It is the poorest country in South America...
in cloud forest
Cloud forest
A cloud forest, also called a fog forest, is a generally tropical or subtropical evergreen montane moist forest characterized by a persistent, frequent or seasonal low-level cloud cover, usually at the canopy level. Cloud forests often exhibit an abundance of mosses covering the ground and...
at elevations from 1800 to 3200 m (5,905.5 to 10,498.7 ft). It occurs in the same general area as its congener N. keaysi, but at higher altitudes.
In 1902, Oldfield Thomas
Oldfield Thomas
Oldfield Thomas FRS was a British zoologist.Thomas worked at the Natural History Museum on mammals, describing about 2,000 new species and sub-species for the first time. He was appointed to the Museum Secretary's office in 1876, transferring to the Zoological Department in 1878...
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". In 1944, Philip Hershkovitz
Philip Hershkovitz
Philip Hershkovitz was an American mammalogist. Born in Pittsburgh, he attended the Universities of Pittsburgh and Michigan and lived in South America collecting mammals. In 1947, he was appointed a curator at the Field Museum of Natural History in Chicago and he continued to work there until his...
relegated both O. levipes and O. keaysi to the synonymy
Synonym (taxonomy)
In scientific nomenclature, a synonym is a scientific name that is or was used for a taxon of organisms that also goes by a different scientific name. For example, Linnaeus was the first to give a scientific name to the Norway spruce, which he called Pinus abies...
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
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....
of the skull is narrow. The incisive foramina
Incisive foramen
The fossa incisiva is an opening in the bone of the oral hard palate where blood vessels and nerves may pass. There are four of these openings in the incisive fossa.-Formation:...
, which perforate the palate
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 separate. The palate is divided into two parts, the anterior...
between the incisor
Incisor
Incisors are the first kind of tooth in heterodont mammals. They are located in the premaxilla above and mandible below.-Function:...
s and the molars
Molar (tooth)
Molars are the rearmost and most complicated kind of tooth in most mammals. In many mammals they grind food; hence the Latin name mola, "millstone"....
, are long and narrow. The bony palate is short, with its posterior end often located between the third molars. The alisphenoid strut
Alisphenoid strut
In some rodents, the alisphenoid strut is an extension of the alisphenoid bone that separates two foramina in the skull, the masticatory–buccinator foramen and the foramen ovale accessorius...
, an extension of the alisphenoid bone of the skull that separates two foramina (openings) in the skull, is present in some individuals. The mastoid bone usually contains some openings. In the holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
, 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.
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.
- Musser, G.G. and Carleton, M.D. 2005. Superfamily Muroidea. Pp. 894–1531 in Wilson, D.E. and Reeder, D.M. (eds.). Mammal Species of the World: a taxonomic and geographic reference. 3rd ed. Baltimore: The Johns Hopkins University Press, 2 vols., 2142 pp. ISBN 978-0-8018-8221-0
- 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.
- Weksler, M., A. R. Percequillo, and R.S. Voss. 2006. Ten new genera of oryzomyine rodents (Cricetidae: Sigmodontinae). American Museum Novitates 3537:1–29.
- Zeballos, H., Vargas, J. and Weksler, M. 2008. . In IUCN. 2008 IUCN Red List of Threatened Species. Retrieved on April 24, 2009.