A fossil of a pterodactyl, the earliest known flying vertebrate, shows the creatures had unique and complex wing fibers that enabled them to fly with the precision and control of birds, researchers said on Wednesday.

The finding by a team of Brazilian, German, Chinese and British researchers in China backs up the theory that the reptiles that dominated the skies from up to 220 million years ago, were not just basic gliders.

A new technique that involves shining ultra-violet rays on the well-preserved fossil found in Inner Mongolia brought out a detailed view of the tissue in the wing of the pterodactyl, also known as pterosaurs, researchers said at a news conference on Wednesday in Rio de Janeiro.

They also found hair-like fibers different from any other animal's that covered the creature's body and part of its wings. This could have helped the animals control their body temperature and shows they were warm-blooded, said Alexander Kellner, a paleontologist at Brazil's National Museum in Rio.