During the Pliocene period some three million years ago, there lived a bull-sized rodent in what is now South America. A new study suggests these creatures used their 11-inch (30 cm) long incisors for more than just eating, using them like tusks to defend themselves and for digging food.

Artistic impression of Josephoartigasia monesi by James Gurney.

Weighing in at an impressive 2,200 pounds (1,000 kg), this massive rodent, named Josephoartigasia monesi, stood 5 feet (1.5 meters) tall and measured nearly 10 feet (3 meters) in length. Back in 2007, a single fossilized skull was discovered in Uruguay. This skull, which measures 20.8 inches (53 cm) long, has now undergone a CT scan to determine just how powerful its bite really was.

With the help of a computer simulation, researcher Philip Cox and colleagues simulated the bite force and cranial biomechanics of the now-extinct creature. At the rearmost tooth of the jaw, the rodent was able to exert a bite force measuring about 4,165 newtons — which is about three times stronger than bite forces exerted by tigers and mid-sized crocodiles.

Philip Cox et al./Journal of Anatomy.

The tips of J. monesi's front teeth were capable of pressing down only 1,389 newtons. At the same time, however, these teeth were strong enough to endure three times the stress produced by that bite force, which suggests it was using these teeth for something other than biting. As the researchers note in the study, "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 also say it's possible that these rodents were using these formidable front teeth to defend themselves from predators.

[ BBC | ScienceAAAS ]