Hystricognathi is a subordo of the Rodentia. Hystricognaths exhibit a partial passage of the masseter medialis through the infraorbital foramen as the masseter maxillomandibularis, which being transmitted axially by the rostral surface of the maxilla distiguishes them from the Myomorpha and the Protrogomorpha. The lack of infraorbital plate to which to anchor the masseter lateralis and the relative size of the infraorbital foramen distinguishes hystricognaths from the Sciuromorpha. Families Many, see text The order Rodentia is the most numerous of all the branches on the mammal family tree. ... The maxillae are the largest bones of the face, except for the mandible, and form, by their union, the whole of the upper jaw. ...

There are 18 familiæ within the Hystricognathi, divisible into a dual classification of infraordines, the Phiomorpha and the Caviomorpha. For other uses, see number 18. ... Caviomorpha is an infraorder of hystricognath rodents. ...

Phiomorphan hystricognath familiæ

• Bathyergidae
• Hystricidae
• Petromuridae
• Thryonomyidae

Genera  Atherurus  Hystrix  Thecurus  Trichys The Old World porcupines are large representatives of the terrestrial rodent mammals, distinguished by their spiny covering from which they take their name. ...

Caviomorphan hystricognath familiæ

• Abrocomidae
• Agoutidae
• Capromyidae
• Caviidae
• Chinchillidae
• Ctenomyidae
• Dasyproctidae
• Dinomyidae
• Echimyidae
• Erethizontidae
• Hydrochaeridae
• Myocastoridae
• Octodontidae

Genera Dasyprocta Myoprocta Agouti The Dasyproctidae are a family of South American rodents, comprising three genera. ... Subfamilies  Caviinae  Dolichotinae The Cavy (family Caviidae) is divided in two subfamilies: Subfamily Caviinae: cavies and guinea pigs Genus Cavia, this genus is especially called cavy. ... Genera  Chinchilla  Lagidium  Lagostomus Chinchillas and their relatives viscachas are small, nocturnal mammals native to the Andes mountains in South America and belonging to the family Chinchillidae. ... Genera Dasyprocta Myoprocta Agouti The Dasyproctidae are a family of South American rodents, comprising three genera. ... Genera  Coendou  Sphiggurus  Erethizon  Echinoprocta The New World porcupines are large terrestrial rodents, distinguished by their spiny covering from which they take their name. ... Binomial name Hydrochoerus hydrochaeris (Linnaeus, 1766) The capybara (Hydrochoerus hydrochaeris) is the largest of living rodents (the long extinct rodent Phoberomys pattersoni was significantly bigger. ... Binomial name Myocastor coypus (Molina, 1782) The Coypu (Myocastor coypus) or Nutria is a large, crepuscular, semiaquatic rodent native to South America, but now also present in Europe, Asia, and North America. ... Genera  Octodon  Octodontomys  Octomys  Spalacopus  Aconaemys  Tympanoctomys The Octodontidae are a family of South American rodents. ...

Also see

• Sciurognathi