Mammals took to the skies at least 70 million years earlier than previously thought, scientists say.
V. antiquus is similar to a modern-day flying squirrel
A fossil uncovered in China suggests mammals were trying out flight at about the same time - or even earlier - than birds, the team reports in Nature.
The researchers said the squirrel-sized animal, which lived at least 125 million years ago, used a fur-covered skin membrane to glide through the air.
The creature was so unusual, they said, it belonged to a new order of mammals.
The US-Chinese team said Volaticotherium antiquus, which means "ancient gliding beast", belonged to a now extinct ancestral line and was not related to modern day flying mammals, such as bats or flying marsupials.
Nocturnal bug eater
The fossil was discovered in the Inner Mongolian region of China. The rock beds it was found in date to at least 125 million years ago to the Mesozoic Era, a time when dinosaurs roamed the Earth.
With a length of 12-14cm (5-6in) and weight of about 70g (3oz), the creature was comparable in size and shape to modern-day flying squirrels.
It had a fold of fur-covered skin membrane that stretched between the creature's fore and hind limbs.
The fossil was found in Inner Mongolia, China
This large membrane combined with its light weight suggested it was an agile glider, the researchers said, although probably not deft enough to capture its prey mid-flight.
V. antiquus had elongated limbs, like modern flying mammals, and its skeleton suggested the presence of a stiff tail, which would have acted as a rudder in flight.
The researchers believe the creature was tree-dwelling, nocturnal and, because of its sharp teeth, most likely feasted on a diet of insects.
This new find places the V. antiquus as the earliest known flying mammal. Dr Jin Meng, an author on the paper and palaeontologist at the American Museum of Natural History, said he believed the creature lived between 130 and 165 million years ago.
With the earliest known flying bird, Archaeopteryx, dating to about 150 million years ago, this could mean mammals flirted with air travel before birds.
The earliest record of a bat, capable of controlled flight, dates to about 51 million years ago; while, before this discovery, the earliest known gliding mammal was a rodent that lived 30 million years ago in the Late Oligocene period.
The researchers believe the gaps in the fossil records for flying mammals are because the creatures delicate flying features are difficult to preserve.
Dr Meng said: "This new evidence of gliding flight in early mammals is giving us a dramatically new picture of many of the animals that lived in the age of dinosaurs."
He added: "Establishing a new order probably only happens once, if that, in the lifetime of a lucky palaeomammalogist."