for National Geographic News
A one-ton "fossil rat" has been discovered in South America, scientists announced today. (See pictures of the giant rodent.)
The prehistoric, bull-size creature—the world's largest recorded rodent—has been identified from a well-preserved skull.
The megarodent lived in lowland rain forests between two and four million years ago, perhaps using its massive teeth to fend off saber-toothed cats and giant, flightless, meat-eating birds, researchers say.
The newfound species, called Josephoartigasia monesi, is reported today in a study led by Andrés Rinderknecht of the National Museum of Natural History and Anthropology in Montevideo, Uruguay.
The rodent weighed about 2,200 pounds (1,000 kilograms), based on an analysis of its 21-inch-long (53-centimeter-long) skull, according to the study, published in the new issue of the journal Proceedings of the Royal Society: B.
Found by an amateur paleontologist in a cliff face along Uruguay's southern coast, the skull suggests that the species was twice as heavy as any other known rodent, Rinderknecht said in an email.
"The future can bring big surprises. But at present J. monesi is the largest recorded rodent," he said.
A relative of rats, mice, and guinea pigs, the creature measured some ten feet (three meters) long, nose to tail. The ancient animal looked a lot like the capybara, the world's largest living rodent, also from South America. (Watch video of an anaconda hunting a capybara.)
But the prehistoric mammal belonged to a rodent family with a single surviving member—the pacarana (see photo)—the study says. A rare species weighing up to 33 pounds (15 kilograms), the pacarana is confined to tropical forests in central South America.
J. monesi inhabited forests around river deltas or estuaries, the study suggests.
"It probably fed on aquatic plants and fruits, because its molars are small and not good for grass or other abrasive [vegetation]," Rinderknecht said.
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