One Ton Guinea Pig Cousin Used Gnashers Like Tusks

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Justine Alford

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806 One Ton Guinea Pig Cousin Used Gnashers Like Tusks
James Gurney. Artist's impression of Josephoartigasia monesi.

An ancient, buffalo-sized rodent may have used its immense front teeth for more than chomping through vegetation, a new study has found. After analyzing the animal’s skull, scientists found that its teeth may have been employed like an elephant’s tusks, helping it dig around in the ground and fight off predators. And you thought the rodents lurking in the sewers were scary.

Josephoartigasia monesi is the largest known rodent to have lived on Earth. This beast weighed up to 1,000 kilograms (2,205 lbs), maybe even more, and measured some 1.5 meters (5 ft) in height and 3 meters (10 ft) in length, making it roughly the size of a buffalo or bison. It lived in South America around 3 billion years ago during the Pliocene to early Pleistocene, likely dwelling in estuarine environments or around streams in forest areas, spending its time gnawing away at aquatic plants. Although some have described the species as a giant rat, this herbivore was actually more closely related to guinea pigs or porcupines.


J. monesi is only known from one fossil, an almost complete skull discovered in Uruguay back in 1987. The specimen remained in the hands of a fossil collector for many years until it was donated to Uruguay’s National History and Anthropology Museum more than two decades ago, where it remained unnoticed in a box until finally being scientifically described in 2008. Now, scientists have revisited the specimen in order to investigate this giant rodent’s chomping abilities.

As described in the Journal of Anatomy, scientists from the University of York and The Hull York Medical School started off by CT scanning the fossil, which was used to create a detailed computer model of the skull. Then, the scientists reconstructed its missing lower jaw using a scaled-up version of the jaw from a close modern-day relative, the chinchilla.

Next, they employed a computational technique used in engineering called finite element analysis which calculates stresses and strains in a particular object. This revealed that at the rear of the jaw, the animal had a bite force of more than 4,000 Newtons, which is around three times greater than those of medium-sized crocodiles. At the front of the jaw, however, the rodent had a bite force of around 1,400 Newtons, which is similar to that of a modern-day tiger. Furthermore, they estimate that its massive incisors would have actually been able to withstand almost three times that force.

Taking these data into consideration, the researchers suggest that the front teeth likely played many more roles than just biting through vegetation. They think that the animal probably used them for activities that required extra muscles, for example those in the neck for digging around in the ground for food, or defending itself against predators, just like modern-day elephants use their tusks.


[Via University of York, BBC News, Motherboard and Science]


  • tag
  • Pleistocene,

  • teeth,

  • fossil,

  • rodent,

  • tusk,

  • Josephoartigasia monesi,

  • J. monesi,

  • guinea pig