5-563: 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 Eucaviomorpha The Hystricognathi are an infraorder of rodents , distinguished from other rodents by
10-652: A body structure more like a short-tailed rat . They are social, tunnel-dwelling animals, and live in the Andes Mountains of South America . They are probably herbivorous , although this is not clear. They can be described as medium-sized. Stiff hairs project over the three middle digits of the rear feet. Their massive skulls narrow in the facial areas. Some molecular work suggests that, despite their appearance, they may be more closely related to octodontoids such as degus , nutria , and tuco-tucos than they are to chinchillas and viscachas . The family name
15-408: 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
20-781: 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 . Play behavior has been observed in seven hystricognath families. The caviomorphs chase each other, play-wrestle, and gallop. The longer-legged species chase more often than
25-446: The shorter-legged species. They also rotate their heads and body muscles as a form of play. Abrocomidae Abrocoma Cuscomys † Protabrocoma Chinchilla rats or chinchillones are rodents of the family Abrocomidae . This family has few members compared to most rodent families, with only nine known living species. They resemble chinchillas in appearance, with a similar soft fur and silvery-grey color, but have
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