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. "It's easily one of the most gratifying experiences of my life, and I hope these pictures will help in some way to prevent the loss of this marvellous animal."
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.
Now classified as Laonastes aenigmamus, the animal first caught the eye of international researchers last year in a hunters' market - dead specimens were on sale.
Based on differences in the skull, teeth, bones and other body features together with DNA analysis, scientists initially put the creature in an entirely new rodent family more closely related to rodents in Africa and South America than in Asia.
LAOTIAN ROCK RAT
The animal is so called for its only known habitat - limestone outcroppings in Central Laos
But then a particularly impressive fossil of a long-extinct rodent was unearthed in China last summer, and that prompted experts to wonder whether the kha-nyou might be a living member of the long-gone family.
They went back through the fossil evidence and found that the kha-nyou's skull, teeth, lower jaw-bone and other skeletal characteristics were a striking match to the fossil.
The latest thinking is that the Laotian rock rat belongs in the same group - the otherwise extinct rodent family Diatomyidae.
Dead specimens were first seen in a hunters' market
Mary Dawson, curator emeritus of vertebrate palaeontology at the Carnegie Museum and primary author of the scientific paper which made the re-identification, has reviewed the latest images.
She has confirmed their authenticity. "This is a truly exciting discovery," Dawson said. "Dr Redfield's sighting of the living animal is the first to be recorded scientifically. These are the first photographic images of the recently discovered 'living fossil' Laonastes aenigmamus."