Mesozoic World

The fossil of a tiny, feathered dinosaur that lived 124 million years ago in what is now China could reveal clues about the origins of bird flight.

The creature, named Microraptor, closes the gap in the fossil record between large meat-eating dinosaurs and what is thought to be the earliest bird, Archaeopteryx. The crow-sized dinosaur did not fly but had clawed feet that it probably used to climb trees.

The discovery adds weight to the theory that small dinosaurs took to the branches to escape predators, gradually developing flight. Other scientists argue that fast-running, bipedal dinosaurs evolved the wings, feathers and muscle structure needed to take-off from the ground.

Treasure trove

The Microraptor fossil came from a rock formation in western Liaoning, north-east China, that has yielded more than 1,000 specimens of early birds and feathered dinosaurs.

Xing Xu from the Institute of Vertebrate Palaeontology and Palaeoanthropology (IVPP) at the Chinese Academy of Sciences, Beijing, said a local farmer had collected the fossil. "I first saw it in a private collection - in a farmer's house," Dr Xu said. "Then with the help of my farmer friend, the IVPP got it."

Scientific scrutiny revealed an adult creature about the size of a crow, with curved claws similar to those used by perching birds. Microraptor has been classified as the smallest non-flying member of the theropods, two-legged meat-eaters that walked the planet between 230 million and 66.4 million years ago.

The find "further shortens the morphological gaps between dinosaurs and birds," said Dr Xu. "It suggests that the paleoecology [the ecology of prehistoric organisms] of some bird-like dinosaurs is similar to that of early birds," he added.

Tree-dwellers

The fossil is important because it could resolve a scientific debate about the origins of bird flight. Commenting on the report in the journal Nature, Dr Paul Barrett of the department of Zoology at the University of Oxford in the UK said that an amazing number of fossils had been found in the Liaoning region.

"Many of the new animals are really helping to plug the gap between birds and dinosaurs once and for all," he said. "The new animal shows a number of modifications to the hips, tail and teeth which are in some ways intermediate between those of advanced meat-eating dinosaurs and birds.

"There also appear to have been feathers, adding more evidence to the view that feathers and feather-like structures predated the origin of birds. "Finally, some of the anatomical specialisations of the feet hint at a tree-dwelling habit - this runs contrary to what most scientists think happened in the origin of birds.

"The consensus has it that birds evolved from the 'ground-up' from fast running animals that gradually took to the air through becoming more efficient leapers. "This paper suggests that there might be some currency in an older, less fashionable idea that birds are descended from tree dwellers that evolved flight though a number of intermediate gliding phases."

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