This family contains 3 species placed in a single genus. Chinchilla rats are found in the Andes of South America from southern Peru to northern Chile. They occur in rocky areas and thickets to around 5000 m elevation.
Chinchilla rats are medium-sized (head-body length 150-250 mm), and have a rat-like body with a long pointed nose, large rounded ears, and large eyes. Their legs are unremarkable. The forefeet have 4 digits and the hindfeet 5. Stiff hairs project beyond the nails of the middle hind digits and probably serve as a comb; similar hairs are found in the families Chinchillidae, Ctenomyidae, and Octodontidae. The nails are weakly built. The tail is shorter than the head and body, cylindrical, and well-furred.
The common name of these rats is probably due to their long, dense, and soft fur, which is sometimes sold in fur markets, although it is not as desirably as that of true chinchillas (Chinchillidae).
The skulls of chinchilla rats have long and narrow rostra, a rounded braincase, enlarged bullae, and delicate zygomatic arches. Incisive foramina are especially long and narrow. The lacrimal canal opens on the rostrum. Chinchilla rats are hystricomorphous and hystricognathus, but hystricognathy is not well developed in this group (the angular process of the dentary arises close to the alveolus of the incisor). There is no separate canal or groove for the passage of nerves and blood vessels through the infraorbital canal. Paroccipital processes are short and pressed against the bullae. The dental formula is 1/1, 0/0, 1/1, 3/3 = 30, and the molars, which are unrooted, have high, flat crowns.
These rodents may be colonial. They are probably herbivorous, but their diets, like most other aspects of their biology, are poorly known.
Families of Order Rodentia Suborder Sciurognathi Family Aplodontidae (mountain beaver, sewellel) Family Sciuridae (squirrels) Family Castoridae (beavers) Family Geomyidae (pocket gophers) Family Heteromyidae (kangaroo rats, pocket mice, and allies) Family Dipodidae (birch mice, jumping mice, jerboas) Family Muridae (familiar rates and other rodents) Family Anomaluridae (scaly-tailed squirrels) Family Pedetidae (spring hare, springhaas) Family Ctenodactylidae (gundis) Family Myoxidae (dormice and hazel mice) Suborder Hystricognathi Family Bathyergidae (mole rats, blesmols, and rats) Family Hystricidae (Old World porcupines) Family Petromuridae (rock rat or dassie rat) Family Thryonomyidae (cane rats or grasscutters) Family Erethizontidae (New World porcupines) Family Chinchillidae (Chinchillas and viscachas) Family Dinomyidae (pacarana, branick rats, false paca) Family Caviidae (cavies and guinea pigs) Family Hydrochaeridae (capybara) Family Dasyproctidae (agoutis, acouchis) Family Agoutidae (pacas) Family Ctenomyidae (tuco-tucos) Family Octodontidae (degus, coruros, rock rats) Family Abrocomidae (chinchilla rats, chinchillones) Family Echimyidae (spiny rats) Family Capromyidae (hutias, zagouties, cavies, Indian coneys) Family Heptaxodontidae (Quemi, giant hutias) Family Myocastoridae (nutria, coypu)
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