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Giant rodent stalked S. America, fossils show ; Researchers say oversized guinea pig was big as a buffalo

Posted on: Wednesday, 24 September 2003, 06:00 CDT

Hate cleaning pet cages? It could be worse. At least your guinea pig isn't the size of a buffalo like the creature described today by paleontologists.

Living in lush marshes in Venezuela 6 million years ago, the 1,500-pound Phoberomys (FOE-ber-o-mees) weighs in as the largest rodent ever found. The discovery of two fossil skeletons, including a nearly complete one nicknamed "Goya," is reported in Science magazine.

The formal name of the rodent is Phoberomys pattersoni. The latter term is in honor of Brian Patterson, a Harvard professor who led a fossil-collection expedition to Venezuela in the 1970s.

"It looks like a very large guinea pig, only the animal had a long tail," says paleontologist Marcelo Sanchez-Villagra of Germany's Tubingen University.

Sanchez-Villagra led the research team that discovered the fossils in an arid region of northern Venezuela, a new frontier for paleontology.

Only a few fragmentary fossil teeth of the creature had previously been uncovered, making size estimates uncertain.

While rodents today are small, Phoberomys shows how creatures evolve to fill empty niches in the natural world of their time, says paleontologist Maureen O'Leary of the State University of New York, Stony Brook, who was not involved in the research.

"Certainly paleontologists have known giant rodents existed in the past, but it's good to find these fossils," O'Leary said. "It's not like we can go out and shoot one of these things today."

An isolated continent until 3 million years ago, when the Central American land bridge connected the Americas, South America featured marshes that made an excellent home for the water-loving giant rats. They lived alongside giant turtles and catfish, chewing on grasses with long rodent teeth.

Nine feet long and 4.2 feet tall, Phoberomys had a long tail to help balance its weight as it moved.

Goya had fur, a smooth head with small ears and eyes, and the large tail, which enabled it to balance on two hind legs to watch for predators, Sanchez-Villagra said.

And there were a lot of predators to worry about.

"We know that there were crocodiles in the same location where we found this animal," Sanchez-Villagra said. "They were some of the largest crocs ever -- more than 10 meters [33 feet] long."

Goya also had to worry about a large carnivore called the marsupial cat, and huge flesh-eating birds called phorracoids, he said.

Competition from North American animals and a changing climate likely led to the giant rodent's extinction, he said.

"Many animals from North America made it to South America, and many from the south went north," Sanchez-Villagra said. "When that happened, many of the animals from South America became extinct because of competition."

In a commentary, biologist R. McNeill Alexander of the United Kingdom's University of Leeds suggests they were too slow to escape new predators.

Gannett News Service, with AP contributing

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