Simplicidentata is a group of mammals that includes the rodents and their closest extinct relatives. The term has historically been used as an alternative to Rodentia, contrasting the rodents with their close relatives the lagomorphs. However, Simplicidentata is now defined as including all members of Glires that share a more recent common ancestor with living rodents than with living lagomorphs. Thus, Simplicidentata is a total group that is more inclusive than Rodentia, a crown group that includes all living rodents, their last common ancestor, and all its descendants. Under this definition, the loss of the second pair of upper incisors is a synapomorphic feature of Simplicidentata. The loss of the second upper premolar (P2) has also been considered as synapomorphic for Simplicidentata, but the primitive simplicidentate Sinomylus does have a P2.
Metacheiromys is an extinct genus of placental mammal from extinct paraphyletic subfamily Metacheiromyinae within extinct paraphyletic family Metacheiromyidae in extinct order Palaeanodonta, that lived in North America from the early to middle Eocene.
Simons's spiny rat is a spiny rat species found in Bolivia, Brazil, Colombia, Ecuador and Peru. It was named for American scientific collector Perry O. Simons.
Oligoryzomys is a genus of rodents in the tribe Oryzomyini of family Cricetidae. Many species are known as pygmy rice rats or colilargos. The genus is found from Mexico to Tierra del Fuego and includes approximately 17 species.
The genus Neacomys, also known as bristly mice because of their spiny fur, includes several species of rodents in the tribe Oryzomyini of family Cricetidae. It is most closely related to Oligoryzomys, Oreoryzomys, and Microryzomys. Neacomys species are mainly found in the Amazon basin, but N. pictus occurs in Panama and N. tenuipes in montane Colombia.
The John Day Formation is a series of rock strata exposed in the Picture Gorge district of the John Day River basin and elsewhere in north-central Oregon in the United States. The Picture Gorge exposure lies east of the Blue Mountain uplift, which cuts southwest–northeast through the Horse Heaven mining district northeast of Madras. Aside from the Picture Gorge district, which defines the type, the formation is visible on the surface in two other areas: another exposure is in the Warm Springs district west of the uplift, between it and the Cascade Range, and the third is along the south side of the Ochoco Mountains. All three exposures, consisting mainly of tuffaceous sediments and pyroclastic rock rich in silica, lie unconformably between the older rocks of the Clarno Formation below and Columbia River basalts above.
The white-toothed brush mouse, also known as the white-toothed melomys or white-toothed mouse, is a species of rodent in the family Muridae. It is found only in West Papua, Indonesia. It is the only species in genus Brassomys. Its natural habitats are subtropical or tropical dry forests and subtropical or tropical dry lowland grassland.
Isthmomys is a genus of rodent in the family Cricetidae, belonging to the tribe Reithrodontomyini. Species are:
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.
Nephelomys albigularis, also known as the white-throated oryzomys or Tomes's rice rat, is a species of rodent in the genus Nephelomys of family Cricetidae. Described in 1860, it was the first Nephelomys species to be discovered. It was originally described in the defunct genus Hesperomys as Hesperomys albigularis and considered related to the much smaller H. longicaudatus. By 1894, it was placed in Oryzomys, as Oryzomys albigularis, and associated with what is now Nephelomys meridensis. In the early 1960s, the scope of the species was considerably expanded to include most of the species that are now in Nephelomys, as well as a single name, boliviae, that is currently a synonym of Euryoryzomys nitidus. From 1976 on, several of these were reinstated as separate species.
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.
Sigmodontomys is a genus of rodent in the tribe Oryzomyini of family Cricetidae. It is related to Nectomys and Melanomys and used to be included in Nectomys. It includes two species, Sigmodontomys alfari and the much rarer Sigmodontomys aphrastus, but whether these are indeed each other's closest relatives is uncertain.
Tillodontia is an extinct suborder of eutherian mammals known from the Early Paleocene to Late Eocene of China, the Late Paleocene to Middle Eocene of North America where they display their maximum species diversity, the Middle Eocene of Pakistan, and the Early Eocene of Europe. Leaving no descendants, they are most closely related to the pantodonts, another extinct group. The tillodonts were medium- to large-sized animals that probably feed on roots and tubers in temperate to subtropical habitats.
The Clarkforkian North American Stage, on the geologic timescale, is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from 56,800,000 to 55,400,000 years BP lasting 1.4 million years.
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.
Guy Graham Musser was an American zoologist. His main research was in the field of the rodent subfamily Murinae, in which he has described many new species.
The Santa Rosa local fauna consists of the animals found in the Paleogene fossil site of Santa Rosa in eastern Peru. The age of the Santa Rosa fauna is difficult to determine, but may be Eocene (Mustersan) or Oligocene (Deseadan).
The Wasatch Formation (Tw) is an extensive highly fossiliferous geologic formation stretching across several basins in Idaho, Montana Wyoming, Utah and western Colorado. It preserves fossils dating back to the Early Eocene period. The formation defines the Wasatchian or Lostcabinian, a period of time used within the NALMA classification, but the formation ranges in age from the Clarkforkian to Bridgerian.
The Bridger Formation is a geologic formation in southwestern Wyoming. It preserves fossils dating back to the Ypresian Epoch of the Paleogene Period. The formation was named by American geologist Ferdinand Vandeveer Hayden for Fort Bridger, which had itself been named for mountain man Jim Bridger. The Bridger Wilderness covers much of the Bridger Formation's area.
The San Jose Formation is an Early Eocene geologic formation in the San Juan Basin of New Mexico and Colorado.
