The family Myoxidae contains 26 species in 8 genera. Its members are found in Africa and Europe west to central Asia. They can be divided into 3 subfamilies: Graphiurinae (Graphiurus); Leithiinae (Dryomys, Eliomys, Myomimus, Selevinia); and Myoxinae (Girulus, Muscardinus, Myoxus). The name Gliridae is sometimes used for this group.
Myoxids are small to medium sized rodents, up to about 190 mm in head-body length. They resemble squirrels or chipmunks, with compact bodies and bushy tails (except members of the genera Selevinia and Myomimus, which have sparsely-furred tails). The limbs are relatively short; the feet are broad; and the toes are tipped with short, curved claws. Myoxids have four functional digits on their forefeet and five on their hindfeet. Their bodies are covered with thick, soft fur. Some species have distinctive black facial markings. Most are good climbers, and the arboreal species have well-developed toe pads.
Members of this family are myomorphous, but they differ somewhat from the typical myomorph arrangement of the masseter. Their skulls have an enlarged infraorbital foramen through which passes a slip of the medial masseter, as in other myomorphs, but the zygomatic plate is not as strongly developed as in most other members of the group. Nerves and blood vessels pass through this foramen as well as muscle; myoxids lack the separate infraorbital foramen for the passage of nerves and blood vessels that is found in dipodids. The jugal of myoxids is horizontal and does not meet the lacrimal. The mandibles are unusual in that the angular process is bent outwards, and in some genera it is perforated. Myoxids are sciurognathus.
The dental formula of myoxids is 1/1, 0/0, 0-1/0-1, 3/3 = 16 or 20. The incisors are sharply pointed. Cheekteeth are brachydont, and their occlusal surfaces are made up of a series of cusps and basins or parallel enamel ridges. Selevinia (which is sometimes placed in its own family) has very small teeth that scarcely erupt from the gums. These have a very simple occlusal pattern.
Myoxids are primarily vegetarian, feeding on fruit and nuts, but they also eat invertebrates, birds and their eggs, and sometimes other rodents. Selevinia probably feeds mostly on invertebrates. Myoxids living in temperate regions put on fat during the fall, then become dormant during inclement weather.
The fossil record of this family begins in the Eocene.
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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