Josephoartigasia monesi, an extinct

Extinction

In biology and ecology, extinction is the end of an organism or of a group of organisms , normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point...

 species of South America

South America

South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...

n caviomorph

Caviomorpha

Caviomorpha is the rodent infraorder or parvorder that unites all South American hystricognaths. It is supported by both fossil and molecular evidence.-Origin:...

 rodent

Rodent

Rodentia is an order of mammals also known as rodents, characterised by two continuously growing incisors in the upper and lower jaws which must be kept short by gnawing....

, is the largest rodent known, and lived approximately 4 to 2 million years ago during the Pliocene

Pliocene

The Pliocene Epoch is the period in the geologic timescale that extends from 5.332 million to 2.588 million years before present. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch...

 to early Pleistocene

Pleistocene

The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....

. The species may have weighed 1000 kg (2,204.6 lb), considerably larger than its closest living relative, the pacarana

Pacarana

The Pacarana is a rare and slow-moving nocturnal rodent found only in tropical forests of the western Amazon River basin and adjacent foothills of the Andes Mountains from northwestern Venezuela and Colombia to western Bolivia, including the yungas. One place that it is common is Cotapata National...

. The rodent may have lived in an estuarine

Estuary

An estuary is a partly enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea....

 environment or a delta

River delta

A delta is a landform that is formed at the mouth of a river where that river flows into an ocean, sea, estuary, lake, reservoir, flat arid area, or another river. Deltas are formed from the deposition of the sediment carried by the river as the flow leaves the mouth of the river...

 system with forest communities, and may have eaten soft vegetation.

Classification

J. monesi is known from an almost complete skull, which was recovered from the San José Formation on the coast of Río de la Plata

Río de la Plata

The Río de la Plata —sometimes rendered River Plate in British English and the Commonwealth, and occasionally rendered [La] Plata River in other English-speaking countries—is the river and estuary formed by the confluence of the Uruguay River and the Paraná River on the border between Argentina and...

 in Uruguay

Uruguay

Uruguay ,officially the Oriental Republic of Uruguay,sometimes the Eastern Republic of Uruguay; ) is a country in the southeastern part of South America. It is home to some 3.5 million people, of whom 1.8 million live in the capital Montevideo and its metropolitan area...

. Discovered in 1987, but not scientifically described until 2008, the specimen is preserved in Uruguay's National History and Anthropology Museum. The species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 is one of two in the Josephoartigasia

Josephoartigasia

Josephoartigasia is an extinct genus of rodent from the Early to Late Pliocene that is related to the living pacarana. The genus includes the largest known rodent, Josephoartigasia monesi. It resembles a modern capybara....

genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

, the other being J. magna

Josephoartigasia magna

Josephoartigasia magna is an extinct species of giant rodent. J. magna is known form Pliocene age fossil teeth found in the San Jose Formation, Playa Kiyu, Chapadmalalan, Uruguay. The species was described in 1966 by J. C. Francis and A. Mones and was placed in the genus Artigasia. After restudy, A...

. J. monesi is sometimes called the giant pacarana, after its closest living relative, the pacarana

Pacarana

The Pacarana is a rare and slow-moving nocturnal rodent found only in tropical forests of the western Amazon River basin and adjacent foothills of the Andes Mountains from northwestern Venezuela and Colombia to western Bolivia, including the yungas. One place that it is common is Cotapata National...

 (Dinomys branickii) in the family Dinomyidae

Dinomyidae

Dinomyidae was once a very speciose group of South American 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...

.

Size

The skull of the holotype

Holotype

A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...

 is 53 cm (21 in) long, and the remaining incisor

Incisor

Incisors are the first kind of tooth in heterodont mammals. They are located in the premaxilla above and mandible below.-Function:...

 is more than 30 cm (12 in) in length. The total estimated body length is 3 m (10 ft), with a height of 1.5 m (5 ft).

By comparing the skull with various extant species of rodent, the authors of the original paper estimated a mass between 468 kg (1,031.8 lb) and 2586 kg (5,701.2 lb), with a median estimate of 1211 kg (2,669.8 lb). A later researcher revisited the numbers and came up with a more conservative estimate of 350 kg (771.6 lb) to 1534 kg (3,381.9 lb), with a median of 900 kg (1,984.2 lb). (Compare 800 to 1,400 kg (1,800 to 3,100 lb) for an adult Black Rhinoceros

Black Rhinoceros

The Black Rhinoceros or Hook-lipped Rhinoceros , is a species of rhinoceros, native to the eastern and central areas of Africa including Kenya, Tanzania, Cameroon, South Africa, Namibia, Zimbabwe, and Angola...

.}

There is no dispute that J. monesi replaces Phoberomys pattersoni

Phoberomys pattersoni

Phoberomys pattersoni is an extinct rodent that lived in the ancient Orinoco River delta approximately 8 million years ago. It was the second-largest of the roughly 7 species of its genus. Like many other rodents, Phoberomys was a herbivore with high-crowned premolars and molars...

, a related and somewhat older species that lived in Venezuela

Venezuela

Venezuela , officially called the Bolivarian Republic of Venezuela , is a tropical country on the northern coast of South America. It borders Colombia to the west, Guyana to the east, and Brazil to the south...

 during the Late Miocene

Late Miocene

The Late Miocene is a sub-epoch of the Miocene Epoch made up of two stages. The Tortonian and Messinian stages comprise the Late Miocene sub-epoch....

, as the largest rodent. However, size comparisons are difficult because previous estimates of 400 kg (881.8 lb) and 700 kg (1,543.2 lb) for P. pattersoni were based on forelimb and hindlimb elements, which are not present in the J. monesi specimen.