Oryzomys is a genus of semiaquatic rodents in the tribe Oryzomyini living in southern North America and far northern South America. It includes eight species, two of which—the marsh rice rat (O. palustris) of the United States and O. couesi of Mexico and Central America—are widespread; the six others have more restricted distributions. The species have had eventful taxonomic histories, and most species were at one time included in the marsh rice rat; additional species may be recognized in the future. The name Oryzomys was established in 1857 by Spencer Fullerton Baird for the marsh rice rat and was soon applied to over a hundred species of American rodents. Subsequently, the genus gradually became more narrowly defined until its current contents were established in 2006, when ten new genera were established for species previously placed in Oryzomys.
The transitional colilargo also known as the intermediate lesser grass mouse, is a species of rodent in the tribe Oryzomyini known only from two individuals found in the Federal District in Brazil. Although described as a link between oryzomyine and akodontine rodents and placed in its own genus, Microakodontomys, Weksler and coworkers dismissed it as an aberrant Oligoryzomys.
Microryzomys is a genus of rodent in the tribe Oryzomyini of family Cricetidae. It is closely related to Oreoryzomys, Oligoryzomys, and Neacomys. It contains two species, both restricted to the Andes: M. altissimus and M. minutus.
Nectomys palmipes, also known as the Trinidad nectomys or Trinidad water rat, is a species of semiaquatic rodent in genus Nectomys of family Cricetidae. It is found on the island of Trinidad and on the nearby mainland of Venezuela.
Nectomys is a genus of rodent in the tribe Oryzomyini of family Cricetidae. It is closely related to Amphinectomys and was formerly considered congeneric with Sigmodontomys. It consists of five species, which are allopatrically distributed across much of South America: Nectomys grandis in montane Colombia; Nectomys palmipes on Trinidad and in nearby Venezuela, Nectomys apicalis in the western margins of the Amazon biome, Nectomys rattus in much of Amazonia, and Nectomys squamipes in the Atlantic Forest of Brazil. These species are generally semiaquatic, are normally found near water, and are commonly called water rats.
Nectomys rattus, the small-footed bristly mouse, Amazonian nectomys, Amazonian mouse, or common water rat is a species of rodent in the genus Nectomys of family Cricetidae. It is found in Brazil, Colombia, French Guiana, Guyana, Suriname, and Venezuela, where it lives in a variety of habitats including lowland tropical rainforest, cerrado and caatinga. It is mainly found in areas close to water. It was recognized as distinct only in 2000 and its limits with other Nectomys, including Nectomys apicalis and Nectomys squamipes, remain unclear.
Oryzomys dimidiatus, also known as the Nicaraguan oryzomys, Thomas's rice rat, or the Nicaraguan rice rat, is a rodent in the family Cricetidae. It is known from only three specimens, all collected in southeastern Nicaragua since 1904. Placed in Nectomys upon its discovery, it was later classified in its own subgenus of Oryzomys and finally recognized as closely related to other species now placed in Oryzomys, including the marsh rice rat and Coues' rice rat, which occurs in the same region.
Mindomys hammondi, also known as Hammond's rice rat or Hammond's oryzomys, is an endangered species of rodent in the tribe Oryzomyini of family Cricetidae. Formerly considered to be related with Nectomys, Sigmodontomys, Megalomys, or Oryzomys, it is now placed in then genus Mindomys, but its relationships remain obscure; some evidence supports a placement near Oecomys or as a basal member of Oryzomyini.
Nephelomys keaysi, also known as Keays's oryzomys or Keays's rice rat, is a species of rodent in the genus Nephelomys of family Cricetidae. It is found from southeastern Peru to northern Bolivia on the eastern slope of the Andes in Yungas humid forest at altitudes of 1000 to 2600 m. Although its continued existence is not in serious danger and it is listed as "least concern", destruction of its habitat may pose a threat to some populations.
Aegialomys xanthaeolus, also known as the yellowish oryzomys or yellowish rice rat, is a species of rodent in the family Cricetidae. It belongs to the genus Aegialomys in tribe Oryzomyini, which was not recognized as distinct from Oryzomys until 2006. It is found in coastal Ecuador and Peru. Though it is currently the only formally recognized mainland species of Aegialomys, at least one other exists. The specific name is sometimes incorrectly spelled "xantheolus", without the second "a".
Oryzomyini is a tribe of rodents in the subfamily Sigmodontinae of the family Cricetidae. It includes about 120 species in about thirty genera, distributed from the eastern United States to the southernmost parts of South America, including many offshore islands. It is part of the clade Oryzomyalia, which includes most of the South American Sigmodontinae.
Nectomys apicalis, also known as the western Amazonian nectomys, is a semiaquatic species of rodent in the genus Nectomys of family Cricetidae. It is found east of the Andes in Ecuador, Peru, and Bolivia, east into western Brazil; further to the east, it is replaced by N. rattus. It lives near watercourses in lowland tropical rainforest. Its karyotype has 2n = 38–42, and it probably actually represents several distinct undescribed species.
Nectomys grandis, also known as the Magdalena-Cauca water rat, is a nocturnal, semiaquatic species of rodent in the genus Nectomys of family Cricetidae. It is found in western and northern Colombia at altitudes from sea level to 2000 m, including the basins of the Magdalena, Cauca and Porce rivers. It has two subspecies, N. g. grandis and N. g. magdalenae.
Cerradomys is a genus of oryzomyine rodents from eastern Bolivia, Paraguay, and central Brazil found in cerrado, Caatinga and Gran Chaco habitats.
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. Its generic name is derived from the Ancient Greek word nephelê "mist", referring to the cloud forest habitat of the members of the genus.
Nephelomys moerex is a species of rodent in the genus Nephelomys of family Cricetidae. The type locality is at Mindo in western Ecuador, where it has been recorded together with three other rodents of the oryzomyine group, Sigmodontomys aphrastus, Mindomys hammondi, and Handleyomys alfaroi, as well as three opossums, Chironectes minimus and unidentified species of Didelphis and Marmosa. Mindo is a "tiny agricultural community" located at 0°02'S, 78°48'W and 1,264 metres (4,150 ft) above sea level. It was originally described by Oldfield Thomas as a subspecies of Oryzomys albigularis. It remained synonymized under this species until it was recognized as a separate species when the genus Nephelomys was established for Oryzomys albigularis and related species in 2006.
In anatomy, posterolateral palatal pits are gaps at the sides of the back of the bony palate, near the last molars. Posterolateral palatal pits are present, in various degrees of development, in several members of the rodent family Cricetidae. Many members of the family lack them or have only simple pits, but Arvicolinae and Oryzomyini have more highly developed posterolateral palatal pits. Posterolateral palatal pits are also present in some other rodents, including Glis, Jaculus, Hystrix, Abrocoma, Ctenomys, Chinchilla, and Lagidium.
In mammals, ungual tufts are tufts of hairs at the base of claws of the forefeet and hindfeet. Their presence has been used as a character in cladistic studies of the Cricetidae, a large family of rodents.
In some rodents, the subsquamosal fenestra is an opening between two parts of the squamosal bone, at the back of the skull. It can be seen in lateral view. Most Oryzomyini have the fenestra, but some species, including those in the genera Nectomys, Sigmodontomys, and Melanomys among others, lack it.
Pennatomys nivalis is an extinct oryzomyine rodent from the islands of Sint Eustatius, Saint Kitts, and Nevis in the Lesser Antilles. The only species in the genus Pennatomys, it is known from skeletal remains found in Amerindian archeological sites on all three islands, with dates ranging from 790–520 BCE to 900–1200 CE. No live specimens are known, but there are several historical records of rodents from Saint Kitts and Nevis that could conceivably refer to Pennatomys. The animal apparently belongs to a group within the tribe Oryzomyini that includes many other island-dwelling species.
