This family consists of 1 genus and 1 species found in southwestern Africa.
Dassie rats are squirrel-like, with a long and hairy (but not or only slightly bushy) tails, body 150-200 mm in length, blunt heads, short rounded ears, and large eyes. The limbs are only moderately long, and the feet are narrow, with four main digits and short claws. Bristle-like hairs associated with claws of the hind feet form a sort of comb, probably used in grooming. The fur of a dassie rat is soft and silky, but there is no underfur. Pelage color varies considerably, but is usually some shade of brown, gray, or buff.
The skulls of dassie rats are hystricomorphous, with a greatly enlarged infraorbital canal and an accessory canal or groove that transmits nerves to the rostrum. They are broad and flat in profile, but ridges and crests for the attachment of muscles are not well developed. Auditory bullae are large, and the paroccipital processes are long and curved around the bullae. The zygomatic arches are strongly built, but the jugal does not contact the lacrimal. The palate is long, extending well beyond the toothrow. The lower jaws are hystricognathous but not strongly so; the angular process is only slightly deflected.
The dental formula of petromurids is 1/1, 0/0, 1/1, 3/3 = 20. The incisors are narrow. Cheekteeth are hypsodont but only on one side, resulting in a terraced appearance. Both upper and lower molars have one labial and one lingual fold. The cheekteeth are not evergrowing.
Rock rats live in groups in arid rocky areas. They are active during the day. Group members use a distinctive whistle to warn of predators. Their diet consists primarily of grass stems and leaves, with some insects also included. They do not require free water. Dassie rats squeeze into rock crevices when threatened, and one of their most remarkable characteristics is their ability to flatten their bodies. Their ribs are flexible and their skulls are unusually flat. The females even have their nipples on their sides, rather than on their undersides, so that young can nurse even when their mother is hiding flattened in a crack.
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)<<<<<<<>>>>>>> ARTIODACTYLA CARNIVORA CETACEA CHIROPTERA DASYUROMORPHIA DERMOPTERA DIDELPHIMORPHI DIPROTODONTIA HYRACOIDEA INSECTIVORA LAGOMORPHA MACROSCELIDEA MICROBIOTHERIA MONOTREMATA NOTORYCTEMORPHIA PAUCITUBERCULATA PERAMELEMORPHIA PERISSODACTYLA PHOLIDOTA PRIMATES PROBOSCIDEA RODENTIA SCANDENTIA SIRENIA TUBULIDENTATA XENARTHRA
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