Oldest fossil rodents in South America confirms animals from Africa   PhysOrg - October 12, 2011
In a literal walk through time along the Ucayali River near Contamana, Peru, a team of researchers found rodent fossils at least 41 million years old Ð by far the oldest on the South American continent.

Ancient stone artwork discovered   BBC - August 18, 2009

Prehistoric artwork has been discovered by an amateur archaeologist at a Perthshire mountain range.

Fossil Tooth Remains Of Extinct Rodent Species Discovered: Oldest Find Within This Genus   Science Daily - August 7, 2009

Uruguay: Bull-Size Rodent Discovered -- Biggest Yet National Geographic - January 16, 2008

Laos: 'Fossil' rock rat pictured alive BBC - June 15, 2006

Images have been obtained of a live Laotian rock rat, the animal science now believes to be the sole survivor of an ancient group of rodents. The kha-nyou, as it is known locally, was trapped by an expedition in May. The pictures show a friendly, furry creature about the size of a squirrel that waddles a bit like a duck. Experts say the kha-nyou can trace its line to a rodent family that initial studies had suggested became extinct more than 11 million years ago. The expedition to central Laos was led by a retired Florida State University scientist, David Redfield."We were extremely fortunate in so many ways to be able to do this," he said of the discovery. The kha-nyou was picked up near the village of Doy, close to the Thai border. It was released back into the wild after being photographed and videoed.

New rodent is 'living fossil' BBC - March 9, 2006

A squirrel-like rodent discovered in Laos is the sole survivor of a group that otherwise died out 11 million years ago, according to fossil data. The animal made headlines in 2005 when it was hailed as the only new family of living mammals to be found in 30 years. But scientists now believe it is a "living fossil", the relic of a group of prehistoric rodents once widespread in South East Asia and Japan.

Nature - September 2003

Cow-sized guinea pigs grazed the riverbanks of South America about five million years ago, confirms a newly found skeleton.

This biggest-ever rodent, Phoberomys patersoni, shared its home with two-metre turtles, ten-metre crocodiles and three-metre carnivorous birds. "It was a land of giants," says co-discoverer Marcelo S‡nchez-Villagra of the University of TŸbingen, Germany.

Named Goya, after the Venezuelan site where its bones were found, the buck-toothed behemoth probably weighed in at 700 kilograms and sported a tail. Phoberomys' closest living relative is probably another hefty guinea-pig lookalike, the forest-dwelling pacarana, which weighs 15 kilograms. Today's largest rodent is the sheep-sized capybara, also South American. The continent was once home to several more extinct rodents that weighed more than 100 kg.

Rodents of unusual size

Guinea pigs' ancestors probably arrived in South America from Africa about 40 million years ago. They found a continent with few large herbivores, and evolved to fill the niche - Goya's teeth show that he or she ate grass. Big animals have slower metabolisms, so they need proportionately less food, and their large guts are good for digesting tough plants. But they may have died out due to their sluggish movement. Most successful modern large herbivores, such as antelopes, are long-legged and fleet-footed. Rodents have short legs and big paws, which are good for digging burrows. "Being a really big rodent, you're slower than the competition," says evolutionary biologist Robert McNeill Alexander of the University of Leeds, UK.

The crocodiles, birds and cat-like marsupials that might have eaten Phoberomys were probably not speedy. But the influx of competitors and predators from North America when the two continents joined three million years ago would have been bad news. This and climate change probably finished off the hapless rodent.

Phoberomys was previously known from fossil teeth and a few fragments of bone. S‡nchez-Villagra and his colleagues found Goya's skeleton in the desert region of Urumaco. When Phoberomys lived there, it was swamp.

Few fossils have been found in northern South America, as most of the land is covered in forest. The skeleton will go on display in the Natural History Museum in Caracas. Meanwhile, the world record for the largest-ever marsupial has just doubled.

Diprotodon optatum, a sort of immense wombat, weighed in at about 2,800 kg - not the 1,175 kg previously suggested - calculate Stephen Wroe and his colleagues at the University of Sydney. They base their new estimate on measurements of bones and on comparisons with other animals. Previous figures were "educated guesswork", says Wroe. Some researchers had thought Australia's poor soil could not support enough plants to feed large herbivores. But the animal's sudden weight gain takes it beyond any living land animal apart from elephants.