The fossil is an almost complete, articulated skeleton with a wingspan of just 25 cm, making it about the size of a swallow. Skeletal features, such as curved, long toes, indicate it was a tree-dweller (Illustration: Chuang Zhao)

A beautifully preserved fossil of a tiny pterosaur suggests that the giant pterodactyls that roamed the skies during the late Cretaceous period may have come from much smaller, tree-dwelling ancestors.

The new fossil, which was discovered in 2004 in western Liaoning province, China, is about 120 million years old.

The specimen is an almost complete, articulated skeleton with a wingspan of just 25 centimetres, making it about the size of a swallow, says its discoverer, palaeontologist Xiaolin Wang of the Institute of Vertebrate Paleontology and Paleoanthropology at the Chinese Academy of Sciences in Beijing.

Portions of its skull are not fully fused, which suggests it may not have reached its full adult size, but its well-developed limb bones make clear that it is much older than a hatchling.


The specimen’s toe bones are long and curved, adaptations which are often seen in tree-dwelling birds and which are poorly suited for running along the ground, says Wang.

Tree dweller

These features suggest that the new fossil, which Wang and his colleagues named Nemicoloperus crypticus, was a small, tree-dwelling species that was likely to have fed on insects in the forest canopy.

Its anatomy suggests that Nemicolopterus is a relatively primitive member of the suborder that includes the giant pterodactyls, the largest flying creatures that ever lived.

Because other even more primitive pterosaurs also are small and tree-dwelling, this makes it likely that the giant pterodactyls evolved from an ancestor with similar habits, the researchers say.

Flight clues

“This is a very, very complete specimen of an unusual little pterodactyl,” says Michael Caldwell, a vertebrate palaeontologist at the University of Alberta in Edmonton, Canada.

The new fossil also sheds some light on another mystery of pterosaur evolution – whether pterosaurs began to fly upwards from the ground, or whether they first climbed into trees and then began to glide downwards.

Though not conclusive, the fact that Nemicolopterus shows tree-climbing adaptations such as curved toes suggests that tree-climbing may have preceded flying, says Caldwell.

Journal reference: Proceedings of the National Academy of Sciences, (DOI: 10.1073/pnas.0707728105)

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