Technology & Science

Bison-sized 'Guinea-zilla' roamed South America

Fossil of 700 kg rodent related to guinea pigs found in Venezuela. The 3-metre-long creature ate sea grass, dodged crocs, scientists say.

The fossil of a giant rodent the size of a buffalo has been uncovered in what is now Venezuela.

The roughly 700-kilogram herbivore lived millions of years ago in a South American swamp. It is an evolutionary sibling to today's guinea pigs, scientists say.

Dubbed Goya, the fossil was unearthed in a semidesert area of Venezuela, about 400 kilometres west of Caracas in the town of Urumaco.

The rodent, Phoberomys pattersoni is named for Brian Patterson, a Harvard professor who led a fossil-collecting expedition to Venezuela in the 1970s.

Marcelo R. Sanchez-Villagra of the University of Tubingen in Germany is the first author of a study describing the creature. The paper appears in Friday's issue of the journal Science.

The furry rodent had a smooth head with small ears and eyes. No one knows why it died out.

Sanchez-Villagra said the three-metre-long Goya roamed the banks of an ancient river some six to eight million years ago. An analysis of the creature's teeth suggests it dined on sea grass.

"Imagine a weird guinea pig, but huge, with a long tail for balancing on its hind legs and continuously growing teeth," said Sanchez-Villagra in a release.

It balanced on its hind legs to watch out for predators such as monster crocodiles, large marsupial cats and huge carnivorous birds called phorracoids, he said.

"Phoberomys is reported to be the largest rodent that ever existed," Sanchez-Villagra and colleagues in Venezuela and the United States wrote in the report.

A big-boned fossil

The leg bones in the skeleton suggest Goya walked differently from most modern rodents, according to the researchers. The fossil is 90 per cent complete.

Mice, rats and guinea pigs scamper about in a crouched position with their legs bent at the knee and elbow. But the huge Goya had to stand straight, wrote McNeill Alexander of the University of Leeds in Britain in an essay accompanying the study.

"The question that puzzles me is not how Phoberomys could have been so large, but why the overwhelming majority of rodents are so small," Alexander wrote.

South America was an island for millions of years until a land bridge called the Panamanian isthmus emerged to connect Central and South America about three million years ago.