An ostrich-like rhino-sized dinosaur

Jun 14, 2007 07:41 GMT  ·  By

An ostrich would look like an undernourished dwarf beside a huge beaked feathered dinosaur recently discovered in China's Gobi Desert.

The ostrich-like dino weighed as much as a rhino (around 1.5 tons) and was over 16 ft (5 m) tall, being the biggest feathered animal ever and the largest toothless dinosaur known so far.

Gigantoraptor erlianensis lived 70 million years ago, to the end of the dinosaur era, when it reached an evolutionary peak.

The fossil belongs to a young individual, so the fully-grown Gigantoraptor was considerably heavier. This giant also makes us think about how dinosaurs evolved into birds. Most concepts state that the two-legged feathered theropod dinosaurs tended to evolve progressively smaller, but the new discovery contradicts this.

"We thought previously that we had a relatively simple pattern-as dinosaurs became smaller in size they became more birdlike. Now, after the discovery of Gigantoraptor, things get more complicated." said lead researcher Xing Xu from the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, China.

The new species is an oviraptorosaur, a group of bird-like dinosaurs, most of them turkey-sized, with feathers on arms and tail.The previously largest known oviraptosaur was emu-sized.

"While the dinosaur's remains didn't include any feathers, which rarely fossilize, its close link to more primitive feathered oviraptorosaurs suggest it very likely did have a feathered tail and arms," said Xu.

"Previously the biggest known feathered animal was an 1,100-pound (500-kilogram) prehistoric flightless bird that lived in Australia six to eight million years ago," he added, pointing to Dromornis, a relative of ducks and geese.

Oviraptorosaurs could have used their long feathers for display and egg incubation.

"This is one of the hypotheses to explain how long feathers evolved on arms," Xu said.

"Gigantoraptor may also account for huge clutches of fossilized theropod eggs measuring 10 ft (3 m) in diameter previously found in China. The species shows gigantism needs not to be correlated with loss of birdness in theropod dinosaurs," said Luis M. Chiappe, director of the Dinosaur Institute at the Natural History Museum of Los Angeles County.

"The fossil also revealed various unexpected features, including more birdlike arms and legs than those seen in related dinosaurs. It looks like it has a number of features which are present in birds which it didn't inherit from its own relatives. Those birdlike features may have appeared once in this animal and once in birds," said dinosaur researcher Paul Barrett of the Natural History Museum in London, England.

The toothless dinosaur has some herbivorous traits like a small head and a long neck, but it was equipped with fearsome claws 20 cm (8 inches) long.

"The claws are so long they are more like those of a meat-eating dinosaur. Maybe it ate small animals, or clams, or plant seeds, or even eggs," said Xu.

Scientists believe this dinosaur had a fast bird-like growth rate, rather than the slow one like in other large theropods (T-rex is the most known example).