An artist's reconstruction for the four-winged, feathered dinosaur Anchiornix huxleyi.
Credit: Zhao Chuang andXing Lida
PARIS: The remains of a ‘four-winged’ dinosaur in China has resolved the ‘temporal paradox’ in palaeontology, confirming that birds owe their ancestry to two-footed dinosaurs.
Xing Xu of the Chinese Academy of Science in Beijing is staking the claim thanks to a well preserved fossil of a bird-like dinosaur called Anchiornis huxleyi. Until now, A. huxleyi was thought to be a primitive bird. It was presumed to have been a near-contemporary of Archaeopteryx, the first recognised bird, which lived around 150 million years ago.
Fossil resolves ‘temporal paradox’
But these opinions were based on an incomplete fossil. The new, nearly complete specimen revealed that A. huxleyi is in fact millions of years older than Archaeopteryx and has both dinosaur and avian features.
It is the long-sought evidence that proves birds descended from theropod dinosaurs, argues Xu, whose work was published in the British journal Nature on Friday.
Scientists have long argued about the evolutionary line taken by birds. Some have said bird-like dinosaurs appear too late in the fossil record to be the true ancestors of birds, an argument known as the "temporal paradox".
The debate has raged for years mainly because the fossil evidence is so rare or fragmented. The new evidence comes from in Daxishan, in Jianchang county in northeastern China.
151 to 161 million years old
It was found in rock dated to the early part of the Late Jurassic, between 151 and 161 million years ago, which means it is clearly older than Archaeopteryx.
Rather than be considered a bird, A. huxleyi is a late member of the Troodontidae, a group of dinosaurs closely related to avians, the study argues. "This new find refutes the ‘temporal paradox’ and provides significant information on the temporal framework of theropod divergence," it says.
The researchers describe the dinosaur as having long feathers covering its arms, tail as well as its feet. This is an arrangement that Xu says is "four-winged", although this gives no guarantee that the creature had aerial ability. In contrast, its elongated lower legs suggest it was a good runner.
Some evolutionary biologists have suggested that a four-winged condition played a role in the origin of flight, but others oppose this idea. The plumage attachment is especially important because it shows how bird-like dinosaurs developed skeletal and other features enabling them to have feathers, the paper says.
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