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Hystricognathi

(Infraorder)

Overview

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Anatomy

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Hystricognathi is an of rodents. Hystricognaths are distinguished from other rodents by the bone structure of their skulls. The masseter medialis (a jaw muscle) passes partially through 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.

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

Skull of a Nutria demonstrating the hystricognathous lower jaw and hystricomorphous zygomasseteric system

Behavior

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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 the shorter-legged species. They also rotate their heads and body muscles as a form of play (Fagen 1981).

Phiomorphan Hystricognath Familiæ

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Caviomorphan Hystricognath Familiæ

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Photos

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Taxonomy

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The Infraorder Hystricognathi is a member of the Suborder Hystricognatha. Here is the complete "parentage" of Hystricognathi:

The Infraorder Hystricognathi is further organized into finer groupings including:

Families

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Abrocomidae

Chinchilla rats are members of the family Abrocomidae. They resemble in appearance, with a similar soft fur and silvery-grey color, but have 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. [more]

Agoutidae

The Dasyproctidae are a family of large rodents, comprising the agoutis and acouchis. Their fur is a reddish or dark color above, with a paler underside. They are herbivorous, often feeding on ripe fruit that falls from trees. They live in burrows, and, like squirrels, will bury some of their food for later use. [more]

Bathyergidae

The blesmols, also known as mole rats, or African mole-rats, are burrowing rodents of the family Bathyergidae. They represent a distinct evolution of a subterranean life among rodents much like the of North America, the tuco-tucos in South America, or the fossorial muroids. [more]

Bathyergoididae

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Capromyidae

Hutias are moderately large -like rodents that inhabit the Caribbean Islands. They range in size from 20 to 60 cm (7.9 to 24 in), and can weigh up to 7 kg (15 lb). 20 species of hutia have been identified, and half may be extinct. Among those that perished were the giant hutias. They resemble the nutria in some respects and the largest species weigh up to seven kilograms. Tails are present, varying from vestiges to prehensile. They have stout bodies and large heads. Most species are herbivorous, though some consume small animals. Instead of burrowing underground, they nest in trees or rock crevices. Only a few species are common, while others have become endangered. [more]

Caviidae

The Cavy (Caviidae) is a family of rodents native to South America, and including the domestic guinea pig, wild cavies, and the capybara, among other animals. They are found across the continent, in open areas from moist savanna to thorn forests or scrub desert. [more]

Chinchillidae

The family Chinchillidae contains the , viscachas, and their fossil relatives. They are restricted to southern and western South America, often in association with the Andes. They are large rodents, weighing from 800 g (28 oz) to 8 kg (18 lb), with strong hind legs and large ears. All species have thick, soft fur, which is considered valuable in some species. [more]

Dasyproctidae

The Dasyproctidae are a family of large rodents, comprising the agoutis and acouchis. Their fur is a reddish or dark color above, with a paler underside. They are herbivorous, often feeding on ripe fruit that falls from trees. They live in burrows, and, like squirrels, will bury some of their food for later use. [more]

Diamantomyidae

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Dinomyidae

The family Dinomyidae was once a very successful group of hystricognath rodent, but now contains only a single living species, the Pacarana. The Dinomyidae included among its ranks the largest rodents known to date, the bison-sized Josephoartigasia monesi and the smaller Josephoartigasia magna. It is thought that the dinomyids were able to occupy ecological niches associated with large grazing mammals due to the lack of true ungulates in South America until its later connection to North America. The modern pacarana is only modest sized, considerably smaller than the capybara. [more]

Echimyidae

The spiny rats are a group of rodents in the family Echimyidae. They are distributed from central Central America through much of South America. They were also found in the West Indies until the 1800s. Some authorities consider the nutria from southern and central South America to be a part of this family. [more]

Eocardiidae

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Erethizontidae

The New World porcupines, or Erethizontidae, are large arboreal , distinguished by the spiny covering from which they take their name. They inhabit forests and wooded regions across North America, and into northern South America. Although both the New World and Old World porcupine families belong to the Hystricognathi branch of the vast order Rodentia, they are quite different and are not closely related. [more]

Heptaxodontidae

The giant hutias are an group of large rodents known from fossil and subfossil material in the West Indies. One species, Amblyrhiza inundata, is estimated to have weighed between 50 and 200 kg (110 and 440 lb), big specimens being as large as an American Black Bear. This is much larger than Capybara, the largest rodent living today, but still much smaller than Josephoartigasia monesi, the largest rodent known. These animals may have persisted into historic times and were probably used as a food source by aboriginal humans. All giant hutias are in a single family Heptaxodontidae, which contains no living species. [more]

Hydrochoeridae

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Hystricidae

The Old World porcupines, or Hystricidae, are large terrestrial , distinguished by the spiny covering from which they take their name. They range over the south of Europe, most of Africa, India, and the Malay Archipelago as far east as Borneo. Although both the Old World and New World porcupine families belong to the Hystricognathi branch of the vast order Rodentia, they are quite different and are not closely related. [more]

Kenyamyidae

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Myophiomyidae

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Neoepiblemidae

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Octodontidae

The Octodontidae are a rodents, restricted to south-western South America. Thirteen species of octodontid are recognised, arranged in nine genera. The best known species is the Degu, Octodon degus. [more]

Petromuridae

The Dassie Rat, Petromus typicus, is an rodent found among rocky outcroppings. It is the only living member of its genus, Petromus, and family, Petromuridae. The name "dassie" means "hyrax" in Afrikaans, and the two animals are found in similar habitats. Petromus means "rock mouse" and dassie rats are one of many rodents that are sometimes called rock rats. The family and genus names are sometimes misspelled as Petromyidae and Petromys. [more]

Phiomyidae

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Thryonomyidae

The genus Thryonomys, also know as cane rats, grass cutters, or cutting grass, is a genus of found throughout Africa south of the Sahara, the only members of the family Thyronomyidae. They are eaten in some African countries and are a pest species on many crops. [more]

At least 20 species and subspecies belong to the Family Thryonomyidae.

More info about the Family Thryonomyidae may be found here.

References

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Sources

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Last Revised: November 19, 2008