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Tuesday, 26 December, 2000, 19:04 GMT
The feathered dinosaurs of Liaoning
Astonishing fossils are being pulled out of the ground in the remote hills of Liaoning Province, China. The specimens, particularly those of tiny, feathered dinosaurs, are fuelling the debate about the origin of birds. Martin Redfern of BBC Science reports.
Slowly but smoothly, the night train glided north-east from Beijing into Liaoning Province. By six in the morning we had reached the bustling city of Jinzhou from where we continued on a white-knuckle taxi ride, praying that the next corner would not conceal a lorry attempting to overtake a donkey cart on the wrong side of the road.
What lured him back were not the overnight train rides or the bumpy roads but the fantastic fossils that are being uncovered in the hills of Liaoning.
We drove between parched, brown fields and passed low mud-brick farms. An icy wind blew from Siberia to the north. The farmers buttoned up their coats against the chill as they gathered every last scrap of vegetation in the hope that they could keep their donkeys alive through another winter. Two years of drought have also meant these are impoverished people.
But as we came to the little village of Sihetun, there was a subtle difference. There were a few modern villa-style homes and some of the young men were riding new Japanese motorbikes. Clearly, there was an additional source of income here.
Fluff to feather
We found it on the hillside just behind the village. In what looked like a huge quarry, researchers were excavating some of the most exciting fossils yet discovered: dinosaurs with feathers.
The fossils have been dated to 124 million years ago, in the lower Cretaceous period. At that time, there was a shallow lake here and anything that fell into it soon got buried under mud and volcanic ash. As a result, many skeletons have been preserved intact. The fine shales even display traces of the creatures' feathers.
Most of them seem to belong to the group of dinosaurs called dromeosaurs. These are the little fast-moving creatures such as Velociraptor, made famous by the film Jurassic Park. They in turn belong to the larger group known as theropods, which includes the mighty carnivore Tyrannosaurus Rex.
The most dinosaur-like examples were clearly too heavy to fly and their feathers were too small and primitive. One species, called Sinosauropterix, had only a faint fuzz of fibres around its body; these may have been downy feathers, though others suggest they could have been hair or flaps of skin.
Dr Zhou Zhonghe points out that the smaller a dinosaur was, the harder it would have been for the creature to control its body temperature. Perhaps, the first feathers developed for thermal insulation and later for display.
Some have suggested that larger relatives were warm blooded and that their babies would have benefited from insulating down. It is strange to think that the terrible T. Rex may have hatched cute fluffy chicks!
The palaeontologists are searching hard to find missing links between birds and dinosaurs. In 1999, they thought they had one. It was purchased in the US for $80,000 from a dealer.
A small fraction of that money had probably helped to buy a Chinese farmer a motorbike before the fossil was smuggled out of the country. The export of vertebrate fossils from China is illegal but some of the local officials who are meant to enforce the law seem to have acquired fine specimens themselves.
The supposed "missing link" was named Archaeoraptor and was featured as the cover story in National Geographic magazine. But it was soon found to be a fake, a composite of a bird-like creature with the tail of a more primitive theropod dinosaur.
When a layered rock is split open to reveal a fossil, you are left with two halves - part and counterpart. The breakthrough in this story came when Xu Xing of the Institute of Vertebrate Palaeontology was able to purchase, for a mere $5,000, the counterpart of the tail stuck on to Archaeoraptor.
With it came the animal that really belonged to the tail, and it was the smallest theropod dinosaur ever found. It was named Microraptor and the discovery was reported in the journal Nature in December 2000.
About the size of the pigeon, Microraptor also had feathers. It had relatively powerful, long legs and might have been able to fly with a good run-up on the ground. But it is more likely that it was a tree climber.
Microraptor had the sort of curved, pointed claws on its feathered forelimbs or wings that are seen in things like woodpeckers and squirrels, which climb tree trunks. One toe on each hind leg is pointed back as in birds, for perching. Maybe it could launch itself from the branches and at least glide if not fly.
There are still those who dispute hotly that theropod dinosaurs gave rise to birds and they have one undeniable piece of evidence in their favour. The oldest known bird, Archaeopteryx, from Germany, is 26 million years older than the feathered theropods from Liaoning, so the latter could not have been their ancestors.
Zhou Zhonghe's PhD supervisor in Kansas, Professor Larry Martin, disagrees with his student and thinks that birds and dinosaurs had a common ancestor far further back in the geological record.
But for most fossil experts, the evidence is clear. The feathered dinosaurs of Liaoning have many features in common with birds and not only feathers. They have a primitive wishbone, the bone in the chest that braces the body against the flight muscles in birds. And they have a characteristic half-moon shaped bone in their wrists, which enables birds to flap their wings wide. The debate is bound to continue but the number and quality of fossils still being discovered in Liaoning means that there will be plenty more evidence.
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