Hystricognathi

The porcupines ( Hystrix leucuta here ) are among the Hystricognathi.

Hystricognathi is a partial order of rodents ( Rodentia ).

To date 230 extant species have been described in 68 genera. The Hystricognathi be divided into two infra- orders: the Phiomorpha, which are restricted to the Old World, as well as restricted to the New World Caviomorpha (guinea pig relatives). The Old World Hystricognathi ( Phiomorpha ) include four extant families: the sandy graves ( Bathyergidae ), porcupines ( Hystricidae ), the rock rat ( Petromus typicus ) and the cane rats ( Thryonomys ). The New World Hystricognathi however, are diverse and include 13 extant families, which are classified into four superfamilies: the Baumstachlerartigen ( Erethizontoidea ), the guinea pig -like ( Cavioidea ), the chinchilla -like ( Chinchilloidea ) and the mirage -like rats ( Octodontoidea ). The closest relatives ( sister group ) of Hystricognathi are the Gundis ( Ctenodactylidae ), limited to North Africa rodent family.

Features

The Hystricognathi differ from other rodents by various anatomical features of the mandible and skull construction. The eponymous feature is the hystricognathe mandible: The Sprouting from the rear end of the lower jaw Angularfortsatz is not in line with the rest of the jaw, as in other rodents with sciurognathem Kieferbau is the case, but is angled sideways. The masseter muscle (musculus masseter medialis), a jaw muscle, thereby extends partially through the infraorbital foramen ( "Under eye hole "). In addition to representatives of this partial order lacks the infra-orbital plate.

Distributional history

Origin and distribution history of Hystricognathi are controversial. Some of the oldest representatives were from the early Upper Eocene described ( about 37 Mya ) from the Fayum oasis in northern Egypt. In South America, the group appears in the early Oligocene (31 Mya ). South America was isolated throughout the Tertiary of Africa and North America; Fossils of Hystricognathi, however, were found exclusively in South America, Africa and Eurasia. Which way the Hystricognathi South America reached is therefore unknown. North America reached the group only after a land bridge was formed three million years ago with the Isthmus of Panama; this land bridge led to a broad faunal exchange between North and South America ( " Great American Faunentausch ").

Families

The partial order Hystricognathi consists of 19 families, which are divided into two infra- orders:

Infraorder Phiomorpha

• Sand burial ( Bathyergidae )
• Porcupines ( Hystricidae )
• Petromuridae Wood, 1955, with the rock rat ( Petromus typicus A. Smith, 1833) as the only way
• Cane rats ( Thryonomyidae Pocock, 1922) with the genus Thryonomys

Infraorder Caviomorpha

• Chinchilla rats ( Abrocomidae ) genus Abrocoma
• Genus Cuscomys

• With the single genus Cuniculus with two types

• Only extant genus Dinomys with the Pacarana ( Dinomys branickii Peters, 1873) as the only way

• With the genus myocastor and Nutria ( Myocastor coypus Ameghino, 1904) as the only way