Josephoartigasia monesi

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†Josephoartigasia monesi
Fossil range: Pliocene to Pleistocene[1]

Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Rodentia
Suborder: Hystricomorpha
Family: Dinomyidae
Genus: †Josephoartigasia
Species: †J. monesi
Binomial name
†Josephoartigasia monesi[1]
Rinderknecht & Blanco, 2008

Josephoartigasia monesi is the largest known rodent, and lived approximately 4 to 2 million years ago in South America during the Pliocene or Pleistocene[1][2]. The species may have weighed 1,000 kg (2,200 lb), considerably larger than its closest living relative, the pacarana[1]. The rodent may have lived in an estuarine environment or a delta system with forest communities[1], and may have eaten soft vegetation.[3].

[edit] Classification

J. monesiis known from an almost complete skull, which was recovered from the San José Formation on the coast of Río de la Plata in Uruguay[1]. Discovered in 1987 (though not scientifically described until 2008), the specimen belongs to Uruguay's National History and Anthropology Museum.[4] The species is one of two in the Josephoartigasia genus, the other being J. magna.[1]

[edit] Size

The skull of the holotype is 53 cm (21 in) long, and the remaining incisor 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 with extant species of rodent, the authors of the original paper estimated a mass between 468 kg (1,030 lb) and 2,586 kg (5,700 lb), with a median estimate of 1,211 kg (2,670 lb).[1] A later researcher revisited the numbers and came up with a more conservative estimate of 350 kg (770 lb) to 1,534 kg (3,380 lb), with a median of 900 kg (2,000 lb).[5]

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 kg (880 lb) and 700 kg (1,500 lb) for P. pattersoni are based on forelimb and hindlimb elements, which are not present in the J. monesi specimen.[1]

[edit] References

  1. ^ a b c d e f g h i Rinderknecht, Andrés; Blanco, R. Ernesto (Jan 2008). "The largest fossil rodent" (pdf). Proceedings of the Royal Society B: 923-928. doi:10.1098/rspb.2007.1645. 
  2. ^ 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.
  3. ^ Brahic, Catherine (2008-01-16). One-tonne rodent discovered in South America. New Scientist. Retrieved on 2008-01-16.
  4. ^ Satter, Raphael G. (2008-01-16). Fossil remains of 2,000-pound rodent found. MSNBC. Retrieved on 2008-01-17.
  5. ^ Millien, Virginie (May 2008). "The largest among the smallest: the body mass of the giant rodent Josephoartigasia monesi". Proceedings of the Royal Society B. doi:10.1098/rspb.2008.0087. Lay summary. 
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