'Extinct' rodent found in Laos

In Brief

Paleontology

March 10, 2006|By DENNIS O'BRIEN

A rodent that scientists once branded as an entirely new variety of animal has turned out to be a really old one.

Laonastes aenigmamus looked like something new when conservation biologists spotted it in a Laotian open-air food market last year. Laotians like to roast the animal, which looks like a squirrel and measures 16 inches from nose to tail.

The researchers sent 15 specimens to the Natural History Museum in London, where experts compared the skulls, teeth, bones and its DNA profile with those of known rodents. They also consulted biologists for the Wildlife Conservation Society and the World Wide Fund for Nature, who were both credited with finding the rodent. In May, the museum announced in its journal that the animal, known locally as "Kha-nyou" or rock rat, was part of a new and distinct family of rodents.

But Mary Dawson, a vertebrate paleontologist of the Carnegie Museum of Natural History in Pittsburgh, says her examination of the London specimens shows the creature is actually a surviving member of the Diatomyidae family, believed to be extinct for 11 million years. The rodents once roamed Asia, and have little in common with squirrels in the United States, she said.

Dawson, whose report was published today in Science, based her findings primarily on the tooth enamel and the shape of the animal's lower jaw. She said both match a number of Diatomyidae fossil specimens found over the years, including some well-preserved remains 22 million years old, found in China in June by Chuan-kui Li, a co-author of the Science paper.

The museum researchers who identified the rodent as part of a new family called Dawson's findings "convincing." They noted that while the animal should be considered part of a known family, it is still a new species or member of that family.

The findings are an example of the "Lazarus effect," a term used when animals turn up that were thought to be extinct, Dawson said. A type of javelina, or feral pig, was thought to have disappeared 10,000 years ago before it was discovered in Paraguay about 30 years ago.

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