Mei long seems to have died peacefully as it was catching forty winks (Image: Mick Ellison, American Museum of Natural History)

The first ever remains of a sleeping dinosaur have been found, providing support for the idea that small dinosaurs were the ancestors of flying birds.

Dr Xing Xu, of the Institute of Vertebrate Palaeontology and Palaeoanthropology at the Chinese Academy of Science in Beijing and Dr Mark Norell, of the American Museum of Natural History in New York have found a perfectly preserved 130 million-year-old new species of dinosaur in China.

They report their discovery in this week's issue of the journal Nature.

"This is the first report of sleeping behaviour in dinosaurs," said Xu. "We've never had any other information about a dinosaur sleeping."

The fossilised small two-legged dinosaur was found curled up with its head tucked under its forearm similar to how modern birds sleep.

Dubbed Mei long, which means "soundly sleeping dragon" in Chinese, the dinosaur was about 53 centimetres long or about the size of a large bird. Its size lends support to the theory that the small size of the dinosaur forebears of birds was crucial to their subsequent development of flight.

Skeleton of Mei long (Image: Xu Xing)

"It is one of the most complete skeletons I have ever seen. It is a perfect preservation. We have almost every bone in the skeleton," Xu said. "There is no disturbance. The body is arranged in a life-like posture."

The sleeping skeleton was found near Beipiao City in Liaoning province, an area rich in fossils that have revealed secrets of dinosaur behaviour.

The sleeping posture indicates the characteristic probably originated in dinosaur ancestors of modern birds, said the resarchers.

Judging from its remarkably preserved state and position of the skeleton Mei long died a peaceful, and probably sudden, death.

Unlike other dinosaurs found with their neck extended back in a classic death pose, Mei long seemed to be sleeping contentedly when it died. Xu and Norell are not sure what killed the dinosaur but they said there are several possibilities.

It could have been starved of oxygen, buried under thick layers of volcanic ash or could have been sleeping in a cave or burrow when the roof collapsed.

"What you can see from the skeleton is that it died peacefully, quickly," said Xu.
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