for National Geographic News
The remains of a huge beaked dinosaur with the looks of an ostrich but the weight of a rhino have been discovered in China's Gobi desert, fossil hunters have announced.
The previously unknown dinosaur weighed in around 1.5 tons (1.4 metric tons) and stood more than 16 feet (5 meters) tall—an extraordinary size given its birdlike appearance, say the Chinese researchers who found it. (See a photo gallery of the giant dinosaur.)
Gigantoraptor erlianensis, which lived some 70 million years ago, is the largest toothless dinosaur known to date and possibly the biggest feathered animal ever to have lived, according to a team led by Xu Xing from the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, China.
The research study also suggests the fossil specimen was still relatively young when it died and that a fully-grown Gigantoraptor would have been considerably heavier.
"The size is just amazing," Xu said.
Describing Gigantoraptor in this week's issue of the scientific journal Nature, the researchers say the creature also challenges thinking about the way birds might have evolved.
Most theories suggest two-legged dinosaurs known as theropods gave rise to birds after certain groups became progressively smaller, but Gigantoraptor appears to contradict this evolutionary trend, the paleontologists report.
"We thought previously that we had a relatively simple pattern—as dinosaurs became smaller in size they became more birdlike," Xu said. "Now, after the discovery of Gigantoraptor, things get more complicated.
"That doesn't mean birds aren't descended from dinosaurs, but the transition is very complicated," Xu added. (Related: "'Feathered' Dinosaur Was Bald, Not Bird Ancestor, Controversial Study Says" [June 1, 2007].)
The team says the newly discovered species belonged to a group of theropod dinosaurs called oviraptorosaurs, yet it was about 300 times heavier than earlier fossil relatives found with arm and tail feathers (a picture of one such dinosaur).
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, the team said.
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