Hystricognathi

Hystricognathi Temporal range: Late Eocene–Recent PreꞒ Ꞓ O S D C P T J K Pg N
Capromys pilorides
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Rodentia
Suborder:	Hystricomorpha
Infraorder:	Hystricognathi Tullberg, 1899
Families
Abrocomidae Bathyergidae †Bathyergoididae Capromyidae Caviidae †Cephalomyidae Chinchillidae Ctenomyidae Cuniculidae Dasyproctidae †Diamantomyidae Dinomyidae Echimyidae †Eocardiidae Erethizontidae †Heptaxodontidae Heterocephalidae Hystricidae †Kenyamyidae Myocastoridae †Myophiomyidae †Neoepiblemidae Octodontidae Petromuridae †Phiomyidae Thryonomyidae
Synonyms
Eucaviomorpha

The Hystricognathi are an infraorder of rodents, distinguished from other rodents by the bone structure of their skulls. The masseter medialis (a jaw muscle) passes partially through a hole below each eye socket (called the infraorbital foramen) and connects to the bone on the opposite side. This, together with their lack of an infraorbital plate and the relative size of the infraorbital foramen, distinguishes hystricognaths from other rodent groups.

The 18 families within the Hystricognathi are divided into two parvorders, the Phiomorpha and the Caviomorpha. The Caviomorpha are mostly native to South America, with a few species in the Caribbean and North America, while the Phiomorpha occur in the Old World.