A Rodent as Big as a Buffalo

Eight million years before the invention of cheese and running wheels, the mighty Phoberomys -- a spectacular rodent the size of a buffalo -- roamed the swamps of South America.

To picture what it looked like, “think of a guinea pig and make it really big and you’re getting pretty close,” said zoologist Marcelo R. Sanchez-Villagra of Germany’s University of Tubingen.

The hulking size of this ancient rodent was reported Friday in the journal Science by Sanchez-Villagra and coauthors Orangel Aguilera and Ines Horovitz. The team analyzed a near-complete fossil skeleton and skull unearthed in Venezuela.

Shapes and sizes of the bones indicate that the creature’s nearest living relative is the guinea pig and that it weighed more than 1,500 pounds -- 10 times more than the biggest rodent now living, the sheep-sized capybara.

“My first reaction was nothing but -- Wow!” said Neill Alexander, emeritus professor of zoology at the University of Leeds in England. “It’s so fantastically bigger than any rodent we’ve got today.”

Phoberomys had a long tail, small front limbs and the teeth of a herbivore.

It probably lived in herds at marshy riverbanks -- and faced some fearsome foes. Giant crocodiles lurked in the rivers, and on land there were gigantic, meat-eating birds. “Really nasty predators,” Alexander said.

Nobody knows why rodents of such unusual size no longer tread the planet.

Phoberomys might have disappeared when the swamps dried up. Scientists also speculate that the giant rodent might have been too slow to survive. Rodents are not well-designed for running, and so their best defense against predators is to be really small -- and able to scuttle down holes.