The finding in northern China provides evidence for the theory that birds evolved from a group of small-sized dinosaurs living in the trees rather than on the ground, scientists said.

The dinosaur, Epidendrosarus in Latin, is believed to have been a juvenile about the size of a house sparrow, with a tail the length of its body. The first of its kind to be reported, the fossil has as its most distinctive feature an elongated third digit in the foreleg, not found on other known dinosaurs or birds.

"The extremely elongated third manual digit could assist it in grasping branches in arboreal life, and also as a tool for finding insects in trees," said Zhang Fucheng, paleontologist with the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences.

The foot of the dinosaur is also unique among all dinosaurs with four toes almost on the same level, very similar to those of perching birds.

The two popular theories on flight origin are that either it was acquired from bouncing on the ground or from arboreal life, including jumping, sliding and then flying with wings.

The new fossil is the second evidence found for the latter theory, and dates even earlier than the first evidence, which was also discovered in north China. Though geologists have not reached agreement on the age of the fossil, it is believed to be from the late Jurassic period in the Mesozoic era.

The species is even more similar to advanced birds than to the most primitive bird Archaeopteryx, in terms of arboreal features, Zhang said.

Zhang's paper, which describes the discovery, was published in the latest issue of the German journal Natur Wissenschafften and co-authored as Zhonghe Zhou, Xing Xu and Xiaolin Wang from the same institute.

Scientists declined to specify the location of the fossil deposits to guard against illegal digging and smuggling.

(Xinhua News Agency September 7, 2002)