Jan. 16 (Bloomberg) -- A fossilized skull found at a beach in Uruguay belongs to a newly identified species of rodent that weighed more than a ton and roamed the estuaries of South America alongside saber-toothed tigers.

``Some of the living giants in Africa, the hippopotamus and the elephants, get this big, but there aren't many land creatures that are larger,'' said Ernesto Blanco, who teaches biomechanics at the Universidad de la Republica in Montevideo, Uruguay.

The fossil, discovered in a boulder by an amateur paleontologist, could help expand knowledge about rodents from the Dinomyidae family which were previously identified largely from fragments of jawbones and isolated teeth, said Blanco, co- author of a report on the find in the U.K. journal Proceedings of The Royal Society.

Only one species of Dinomyidae still exists, the endangered pacarana of South America. About 50 fossil species are known. The skull dates to the Pliocene-Pleistocene period, ranging from 2 million to 4 million years ago.

``This is the first time it's been possible to study a complete skull, not just of this species, but of the entire group,'' Blanco said in a telephone interview.

The largest living rodent in the world is the capybara, which is found across South America. Capybaras can weigh 60 kilograms (132 pounds), or 6 percent of the weight of the new species, whose scientific name is Josephoartigasia monesi. Rodents, a group including rats, beavers and squirrels, account for nearly 40 percent of all mammalian species alive today.

`Smart' Cars

Studies of the ``exceptionally well-preserved'' bones indicate that the new rodent weighed in excess of 1,000 kilograms, more than the two-door ``Smart'' cars built by Daimler AG's Mercedes Car Group, according to Blanco.

The creature had weak jaw muscles and the teeth had a relatively small area for grinding, suggesting it may have relied on fruit, soft vegetation or aquatic plants for food.

The skull sat in Uruguay's Museum of Natural History and Anthropolgy for at least five years and probably more than a decade before being studied, Blanco said, adding he and his co- author, Andres Rinderknecht, have a research budget of ``a few hundred dollars'' a year.

``Paleontology is expensive,'' Blanco said. ``You need to have people in the field for a long period. Without more funding, this work probably can't continue.''

To contact the reporter on this story: Bill Faries in Buenos Aires at wfaries@bloomberg.net

Last Updated: January 15, 2008 19:00 EST