Meet gigantoraptor - the feathered one-ton relative of modern birds

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It weighed more than a ton, walked on two legs and was armed with dagger-like claws and a giant, fearsome beak. It is also the latest addition to the growing known menagerie of large, flesh-eating dinosaurs.

Scientists who discovered fossils of the creature, called gigantoraptor, at a site in China said yesterday they were surprised by its size and similarity to modern-day birds - it was even covered in feathers.

Gigantoraptor was at least twice the height of a man at the shoulder and grew more than 26 feet long. At 1,400kg, it was about 35 times heavier than any other feathered dinosaurs known by science. In fact it may have been even bigger, because the specimen unearthed from the Sunitezuoqi region of Inner Mongolia was not fully grown when it perished tens of millions of years ago, scientists said.

Gigantoraptor was the stuff of nightmares. Although it could not fly, it was covered in feathers and had short forelimbs ending in large clawed "hands". The head, which sat on an ostrich-like neck, resembled that of a bird with a powerful snapping beak instead of a toothed jaw.

The dinosaur lived in the late-Cretaceous period, around 70 million years ago, at the same time that Tyrannosaurus rex, one of the largest land carnivores, terrorised what is now North America. Most theories suggest that carnivorous dinosaurs became smaller as they grew more bird-like. But gigantoraptor, which evolved towards the end of the dinosaurs' reign, proved this was not always the case.

A team led by Dr Xing Xu, from the Chinese Academy of Sciences in Beijing, described the find in the journal Nature. The partial skeleton revealed in the first official scientific description of gigantoraptor included pieces of the beak, vertebrae, limb bones, right shoulder blade and pelvis.

Because of its bird-like features, scientists have placed gigantoraptor in the family of oviraptorosuarids, a group of small feathered dinosaurs which rarely weighed more than 40kg.

The scientists wrote: "As an oviraptorosaurian, gigantoraptor is remarkable in its gigantic size."

Bone structure suggested the dinosaur had an unusually fast growth rate, which may explain how it got so big. It also had a number of bird-like features which were absent from its smaller, feathered relatives.

Most experts now believe that modern birds evolved from a branch of small, feathered dinosaurs whose feathers may have evolved originally for warmth but later became useful for gliding flight and then powered flight.