Porcupines are large rodents with coats of sharp spines, or quills, that protect them against predation. The term covers two families of animals: the Old World porcupines of the family Hystricidae, and the New World porcupines of the family Erethizontidae. Both families belong to the infraorder Hystricognathi within the profoundly diverse order Rodentia and display superficially similar coats of rigid or semi-rigid quills, which are modified hairs composed of keratin. Despite this, the two groups are distinct from one another and are not closely related to each other within the Hystricognathi. The largest species of porcupine is the third-largest living rodent in the world, after the capybara and beaver.
The family Chinchillidae is in the order Rodentia and consists of the chinchillas, the viscachas, and their fossil relatives. This family is restricted to southern and western South America, mostly living in mountainous regions of the Andes but one species living on plains. They are medium to large-sized rodents, weighing from 800 g (28 oz) to 8 kg (18 lb), with strong hind legs and large ears and a bushy tail. All species have thick, soft fur, which is considered valuable in some cultures.
Phoberomys pattersoni is an extinct rodent that lived in the ancient Orinoco River delta around 8 million years ago. It was the second-largest of the roughly seven species of its genus. Like many other rodents, Phoberomys was a herbivore with high-crowned premolars and molars.
The pacarana is a rare and slow-moving hystricognath rodent indigenous to South America. Native Tupi people call it the pacarana because it is superficially similar to the paca, a different rodent which is not in the same family. The pacarana has a chunky body and is large for a rodent, weighing up to 15 kg (33 lb) and measuring up to 79 cm in length, not including the thick, furry tail.
The genus Hydrochoerus contains two living and three extinct species of rodents from South America, the Caribbean island of Grenada, California and Panama. Capybaras are the largest living rodents in the world. The genus name is derived from the Greek ὕδωρ 'water' plus χοίρος 'pig'.
Heptaxodontidae, rarely called giant hutia, is an extinct family of large rodents known from fossil and subfossil material found in the West Indies. One species, Amblyrhiza inundata, is estimated to have weighed between 50 and 200 kg, reaching the weight of an eastern gorilla. This is twice as large as the capybara, the largest rodent living today, but still much smaller than Josephoartigasia monesi, the largest rodent known. These animals were probably used as a food source by the pre-Columbian peoples of the Caribbean.
Caviomorpha is the rodent infraorder or parvorder that unites all New World hystricognaths. It is supported by both fossil and molecular evidence. The Caviomorpha was for a time considered to be a separate order outside the Rodentia, but is now accepted as a genuine part of the rodents. Caviomorphs include the extinct Heptaxodontidae, the extinct Josephoartigasia monesi and extant families of chinchilla rats, hutias, guinea pigs and the capybara, chinchillas and viscachas, tuco-tucos, agoutis, pacas, pacaranas, spiny rats, New World porcupines, coypu and octodonts.
Cavia is a genus in the subfamily Caviinae that contains the rodents commonly known as guinea pigs or cavies. The best-known species in this genus is the domestic guinea pig, Cavia porcellus, a meat animal in South America and a common household pet outside of that continent.
Telicomys is an extinct genus of rodent from the Solimões Formation, Brazil, South America.
The Eocardiidae are an extinct family of caviomorph rodents from South America. The family is probably ancestral to the living family Caviidae, which includes cavies, maras, and capybaras and their relatives. McKenna and Bell (1997) divided eocardiids into two subfamilies, Luantinae for two of the oldest genera and Eocardiinae for remaining genera. Kramarz (2006) has recommended the abandonment of these subfamilies, as the genera placed in Luantinae appear to represent basal eocardiids, rather than a specialized side branch. The latter hypothesis had been proposed by Wood and Patterson (1959).
The Neoepiblemidae are an extinct family of hystricognath rodents from South America. The genera Dabbenea and Perumys are now included in Phoberomys. The delineation between Neoepiblemidae and Dinomyidae has historically been unclear, with some genera having varying taxonomic placement. A 2017 study found Phoberomys to be part of the group, while Eusigmomys was found to be part of the Dinomyidae.
The Mylagaulidae or mylagaulids are an extinct clade of sciuromorph rodents nested within the family Aplodontiidae. They are known from the Neogene of North America and China. The oldest member is the Late Oligocene Trilaccogaulus montanensis that lived some 29 million years ago (Mya), and the youngest was Ceratogaulus hatcheri—formerly in the invalid genus "Epigaulus" —which was found barely into the Pliocene, some 5 Mya.
Josephoartigasia is an extinct genus of enormous dinomyid rodent from the Early Pliocene to Early Pleistocene of Uruguay. The only living member of Dinomyidae is the pacarana. Josephoartigasia is named after Uruguayan national hero José Artigas. It contains two species: J. magna, described in 1966 based on a left mandible, and J. monesi, described in 2008 based on a practically complete skull. Both are reported from the San José Member of the Raigón Formation by the Barrancas de San Gregorio along the shores of Kiyú beach.
The Chapadmalalan age is a period of geologic time within the Pliocene epoch of the Neogene used more specifically with South American Land Mammal Ages. It follows the Montehermosan and precedes the Uquian age.
Álvaro Jaime Mones Sibillotte is a Uruguayan biologist and paleontologist.
The Raigón Formation is a Huayquerian-Montehermosan geologic formation in Uruguay.
The Camacho Formation is a Huayquerian geologic formation in Uruguay.
Isostylomys is an extinct genus of dinomyid rodent from the Huayquerian. Fossils have been found at the Ituzaingó Formation in Argentina and Camacho Formation in Uruguay.
