Largest known rodent wielded its enormous teeth like tusks

Scientists have discovered that the largest-known rodent to have ever roamed earth - roughly the size of a buffalo - had ferocious front teeth useful for fighting and digging - much in the way elephants today use their tusks.

The rodent, called Josephoartigasia monesi in the Journal of Anatomy, weighed an estimated one tonne, but its close modern-day relatives include the much smaller guinea pig.

This huge rodent, found in Uruguay and described in a paper in 2008, lived in South America about three million years ago, probably around estuaries near forested areas. Yet it was not the only giant animal at the time, the earlier paper said.

"The possible associated fauna include other giant rodents, sabre-toothed cats, giant carnivorous birds, xenarthrans [mammals lacking incisors and canine teeth], capybaras [large mammals] and assorted ungulates [hoofed mammals]," Andres Rinderknecht of Uruguay's National Museum of Natural History and Anthropology and Ernesto Blanco of the Institute of Physics wrote in 2008.

Aside from its size, one of the huge rodent's distinctive features were its enormous front teeth. Long, sharp incisors are a common feature among rodents such as the teeth of beavers, squirrels, but the ones on Josephoartigasia monesi looked as if they could cause a lot of damage.

To find out what these fearsome teeth were used for, Philip Cox, of Britain's University of York, and the authors of the 2008 study put the fossil through a CT scan, created a computer reconstruction of the skull and modelled the stresses and strains that it could take.