One-Ton Rat Roamed Ancient Swamplands

Jan. 16, 2008 -- Fossil hunters have uncovered the greatest rodent that ever lived -- a one-ton behemoth that bestrode the swamplands of South America some four million years ago.

The newly identified species is the greatest-known member of the order Rodentia and by comparison makes the biggest rodent alive today, the 60-kilo (132-pound) capybara, look like a pygmy shrew.

The skull of the extraordinary beast was found in a broken boulder on Kiyu Beach on the coast of Uruguay's River Plate region, paleontologists reported in a study on Wednesday.

Measuring a whopping 53 centimeters (21 inches), the skull has massive incisors several centimeters long.

Despite this fearsome look, the creature was not carnivorous and looked more like a hippo than a rat.

Its small grinding teeth suggest it had only weak masticatory muscles for chewing food, and probably tucked into soft vegetation, fruit and squidgy aquatic plants in deltas, the experts say.

Its food intake must have been vast, given its huge size.

Other denizens of this world of marsh and forest would have included saber-toothed cats, flesh-eating birds and armadillos.