The creature's official title is stone-dwelling puzzle-mouse and it has been honoured with the Latin name Laonastes aenigmamus.

Less poetically, it is being called a rock rat, or "kha-nyou" to local Laotians.

"(It) looks something like a cross between a large dark rat and a squirrel, but is actually more closely related to guinea pigs and chinchillas," the British weekly magazine New Scientist reports.

The rodent has long whiskers with a thicky, furry tail, large paws, stubby limbs and is around 40 centimetres (16 inches) long.

The discovery was made by Robert Timmins, a member of the New York-based Wildlife Conservation Society, who spotted a dead rock rat as it was about to be grilled as a kebab.

"It was for sale on a table next to some vegetables," said Timmins. "I knew it was something I had never seen before."

Timmins and colleagues subsequently found the animal in rocky limestone outcrops in the Khammouan National Biodiversity Conservation Area in central Laos, but they have never seen it alive.

The discovery is "a major zoological find," New Scientist says.

New rodent species are discovered at the rate of one every year or so.

But what makes the rock-rat special is that it is the first member of a whole new family of mammals, now called Laonastidae.

The last time this happened was in 1974, when the bumblebee bat was discovered.

"To find something so distinct in this day and age is just extraordinary. For all we know, this could be the last remaining mammal family left to be discovered," Timmins told New Scientist.

The report appears in next Saturday's issue of the magazine. The full study appears in a specialist British journal, Systematics and Biodiversity.

Taxonomy classifies living creatures according to progressively narrower definitions: Kingdom, phylum, class, order, family, genus and, finally, species.

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