Guanlong wucaii was found in the Junggar Basin of Xinjiang, China.
 
A fossil dug up in a remote Chinese desert clearly reveals the earliest example of a Tyrannosaur, scientists say.

The Junggar Basin in the far western reaches of China's Gobi Desert have yielded a pair of small hidden dragons, long buried in a mixture of sand, clay, and volcanic deposits.

The researchers, led by Xu Xing of the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, named the new dinosaur Guanlong wucaii, meaning Crested Dragon.

The creature lived 160 million years ago in the Jurassic Period, more than 90 million years before Tyrannosaurus rex, the researchers report in this week's issue of the journal Nature .

"Guanlong is the oldest and most primitive tyrannosaur," said James Clark of George Washington University, who participated in the study.

The creatures were about 3 metres long, compared to Tyrannosaurus rex, the best-known tyrannosaur which lived 65 million to 70 million years ago during the Cretaceous Period. The latter reached lengths of 14 metres.

The most striking feature of the two nearly complete skeletons is a strange crest at the front of the head like that of a rooster, only with a straight top edge rather than a wavy one.

Clark says the structure was unusual among this branch of theropod dinosaurs, the broader line believed to be related to birds. The crest dwindled in size to just a faint ridge in the next known tyrannosaur descendant, a feathered tyrannosaur unearthed in 2004 called Dilong. It was completely gone by the time of T.rex, 90 million years after Guanlong.

Clark says no one knows if the crest belonged to only the male tyrannosaur like a rooster because the gender of the two fossils cannot be determined.

Tyrannosaurs are known to have been meat-eaters.

By the time of T-rex, tyrannosaurs were the dominant predators in eastern and central Asia and North America. They remained so for the last 20 million years of the Late Cretaceous era, which ended at the time all dinosaurs became extinct 65 million years ago.

Editor: Yan