Temporal range: Pliocene to Early Pleistocene 4–2Ma
|Josephoartigasia monesi reconstruction|
Rinderknecht & Blanco, 2008
Rinderknecht & Blanco, 2008
Josephoartigasia monesi, an extinct species of South American caviomorph rodent, is the largest rodent known, and lived approximately 4 to 2 million years ago during the Pliocene to early Pleistocene. The species may have weighed 1,000 kg (2,200 lb), considerably larger than its closest living relative, the pacarana. The rodent may have lived in an estuarine environment or a delta system with forest communities, and may have eaten soft vegetation.
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 in Uruguay. Discovered in 1987, but not scientifically described until 2008, the specimen is preserved in Uruguay's National History and Anthropology Museum. The species is one of two in the Josephoartigasia genus, the other being J. magna.J. monesi is sometimes called the giant pacarana, after its closest living relative, the pacarana (Dinomys branickii) in the family Dinomyidae.
By comparing the skull with various extant species of rodent, the authors of the original paper estimated a mass between 468 and 2,586 kg (1,030 and 5,700 lb), with a median estimate of 1,211 kg (2,670 lb). A later researcher revisited the numbers and came up with a more conservative estimate of 350 to 1,534 kg (770 to 3,380 lb), with a median of 900 kg (2,000 lb). (Compare 800 to 1,400 kg (1,800 to 3,100 lb) for an adult Black Rhinoceros.)
There is no dispute that J. monesi replaces Phoberomys pattersoni, a related and somewhat older species that lived in Venezuela during the Late Miocene, as the largest rodent. However, size comparisons are difficult because previous estimates of 400 and 700 kg (880 and 1,500 lb) for P. pattersoni were based on forelimb and hindlimb elements, which are not present in the J. monesi specimen.
- Rinderknecht, Andrés; Blanco, R. Ernesto (January 2008). "The largest fossil rodent" (pdf). Proceedings of the Royal Society B 275 (1637): 923–928. doi:10.1098/rspb.2007.1645. PMC 2599941. PMID 18198140. Retrieved 2008-05-27.
- According to Rinderknecht & Blanco (2008) recent studies indicate that some strata of the San José Formation in which the specimen was found are Pleistocene, instead of Pliocene as was traditionally assumed. In any case, they do give a date range of 4–2 Mya.
- Brahic, Catherine (2008-01-16). "One-tonne rodent discovered in South America". New Scientist. Retrieved 2008-01-16.
- Satter, Raphael G. (2008-01-16). "Fossil remains of 2,000-pound rodent found". MSNBC. Retrieved 2008-01-17.
- Millien, Virginie (May 2008). "The largest among the smallest: the body mass of the giant rodent Josephoartigasia monesi". Proceedings of the Royal Society B 275 (1646): 1953. doi:10.1098/rspb.2008.0087. PMC 2596365. PMID 18495621. Retrieved 2008-05-27. Lay summary.