Fossil settles dinosaur-bird row
Published 29/01/2010 | 07:58
A creature with pointed teeth, sharp claws and a confused identity has been shown once and for all to be a dinosaur and not a bird.
Haplocheirus sollers lived 15 million years before the first flying bird, Archaeopteryx, and helps dispel any doubt that birds evolved from dinosaurs.
An almost complete fossil skeleton of the 10-foot long dinosaur was unearthed by scientists during an expedition to the Gobi Desert in China in 2004.
Haplocheirus, which lived 160 million years ago, is the oldest known member of an oddball group of bird-like dinosaurs called alvarezsauroids. Their most distinguishing feature was a single huge claw on each hand that may have been used for digging.
Alvarezsauroids are so bird-like that for many years, since their discovery in the 1920s, experts argued about whether they were really dinosaurs. Many insisted the later alvarezsauroids, which were smaller than Haplocheirus, were actually flightless birds.
The new fossil settles the dispute, confirming their dinosaur identity without doubt, and also fills an important gap in knowledge about the evolution of birds.
Most scientists believe modern birds are direct descendants of meat-eating two-legged dinosaurs. But there is an alternative view, that birds evolved quite independently.
Those who challenge the "dinobird" theory point to the fact that all the clearest examples of bird-like dinosaurs only appeared millions of years after the Archaeopteryx. Bird evolution had progressed a long way before they even existed. Haplocheirus bucks this trend, since it lived long before the first bird.
A joint Chinese and US team led by Dr Xu Xing from the Institute of Vertebrate Palaeontology and Palaeoanthropology in Beijing, described the dinosaur today in the journal Science.
Dr Xu pointed out how hard it was to distinguish between birds and dinosaurs. "Deep in evolutionary history, it's extremely difficult to draw the line," he said in a Science news article.