MACHO meat-eating Tyrannosaurus rex had a feathery forefather, which sported a delicate crest on its snout and long slender arms.

This smaller and comparatively dandyish ancestor of fearsome T-rex was discovered in the badlands of Xinjiang in far-western China where it lived in the Late Jurassic period, about 160 million years ago.

"It was a very spectacular animal," said paleontologist Steve Salisbury, of the University of Queensland in Brisbane.

The new dinosaur had a mix of primitive characteristics - like three-fingered hands and blade-like teeth on the sides of its jaw - and more modern T-rex traits such as U-shaped teeth in the front of its upper jaw.

The huge "nasal crest" on the dinosaur's nose was a surprise to the discovery team of Chinese, Canadian and US researchers, led by Xing Xu of the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing.

They speculate today in the journal Nature that it may have been a cumbersome sexual ornament, similar to the peacock's tail and the elk's antlers.

Because the 3m-long dinosaur - named Guanlong wucaii , or "crowned dragon of the five-coloured rocks - and a more recent member of the same lineage, Dilong, apparently had primitive feathers, Dr Salisbury suggested another surprise: that T-rex may also have had a spot of plumage.

"It may have had immature feathers, protofeathers, when it was young," said Dr Salisbury.

He added that some sort of feathered covering was probably a characteristic of all coelurosaurs, a group of swift small-bodied creatures that were ancestral to several groups of bipedal three-toed animals, including birds and the Tyrannosauridae, T-rex and its kin.

The newly discovered dinosaur, probably a "secondary predator", was hailed as a significant find by scientists keen to tease out the evolutionary path taken by T-rex, which lived 65-80 million years ago during the Late Cretaceous period.

Until now, the task was difficult because of a gap in the fossil record, now filled by Dr Xu and his colleagues.

In an accompanying report in Nature, written by paleontologist Thomas Holtz of the University of Maryland, the remains of the two Guanlong show clearly that the beast was "the most ancient known member of the line that led to T-rex and its giant kin".

Leigh Dayton

'Spectacular': An artist's impression of Guanlong wucaii. Picture: Reuters