The largest rodent that ever lived -- the size of a buffalo and weighing more than 2,000 pounds -- might have used its tusk-like front teeth for fighting, researchers suggest.
The giant relative of the guinea pig, which went extinct around 2 million years ago, may have also used its giant front teeth to dig for food, they say.
Scans of a fossil skull of the South American giant Josephoartigasia monesi and computer modeling suggest its bite was as strong or even stronger than that of a modern tiger, but its front teeth -- almost a foot long -- could withstand forces as much as three times as large.
It suggests the 5-foot-tall, 10-foot long creatures were using those front incisors in the same way a modern elephant uses its tusks, researchers from Britain and Uruguay report in the Journal of Anatomy.
"We concluded that Josephoartigasia must have used its incisors for activities other than biting, such as digging in the ground for food, or defending itself from predators," says Philip Cox of the University of York in Britain. "This is very similar to how a modern day elephant uses its tusks."
Cox and his research colleagues used computer simulations and CT scans of the only J. Monesi skull known, found in Uruguay in 1987 but not scientifically described until 2008, to determine the extinct creature's bite force and the biomechanics of its skull.
The animal's bite force at its rearmost teeth measured around 4,165 newtons, about three times that of a modern day tiger or medium-size crocodile, but its front tusk-like teeth were strong enough to endure three times the stress produced by that bite force, the researchers determined.
That suggests those giant front teeth "overengineered" and likely were used for much more than just eating, including tasks that would have involved extra muscles in the creature's neck, the researchers said.
"These results, combined with previous work, lead us to speculate that J. monesi was behaving in an elephant-like manner, using its incisors like tusks, and processing tough vegetation with large bite forces at the cheek teeth," they said.
J. monesi, the largest rodent ever discovered, lived in the Earth's warm Pliocene period when large mammals such as the first mammoths were fairly abundant.
The creatures is sometimes called the giant pacarana, after its closest living relative, the pacarana, although today's creature is much smaller at around 3 feet long.
