New find faster than a T. rex

Paleontologists working in the desert wilderness of northwestern China have unearthed the oldest ancestor yet of Tyrannosaurus rex, a midsize, long-armed predator with razor-sharp teeth and a spectacular inflatable crest atop its snout.

Unlike T. rex, however, Guanlong wucaii – “crown dragon from the land of five colors” – was not the top-of-the-line predator of its time, but scientists suggested Wednesday it could probably outrun anything it could not outfight.

“When you become a giant animal, the entire (body) has to be modified,” said Mark Norell, a paleontologist at the American Museum of Natural History. “This is a very gracile animal; T. rex is elephantine.”

Guanlong, which lived 160 million years ago, predated T. rex by 90 million years and is the oldest tyrannosaur ever found by at least 30 million years. Norell was part of an eight-member discovery team led by Xing Xu, of the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing.

They describe their find today in the journal Nature.

Team co-leader James Clark, of George Washington University, said he and Xu decided to investigate the badlands of the Junggar Basin west of the Gobi desert after Chinese geologists prospecting for oil in the 1970s had mentioned finding fossils there.

“You depend on previous discoveries,” Clark said at a news conference. “You get as many people as you can and start looking at outcrops.” The team has been working in the Basin since 2000 and has dug up several dozen fossils.

Clark said the team found Guanlong in 2002. At first, excavators thought they had only one specimen, but after chipping away the “mud rock” encasing the fossil, they found a second skeleton below the first.

Analysis showed the lower fossil was a “juvenile,” about seven years old, while the top skeleton was a 12-year-old adult. Clark said the mature Guanlong was about 10 feet long, “a not particularly small, not particularly large dinosaur.” T. rex averaged 40 feet long and weighed six tons.

The most distinctive feature of the skeleton was a long, bony crest on top of the snout, unusual for meat-eating dinosaurs. Clark said the crest was a thin membrane over an air-filled sac. Such features, he added, could have evolved for sexual display to attract mates or as distinctive markers for species identification.

Clark said Guanlong had many tyrannosaur-like attributes, including sharp cutting teeth, a flared tailbone, and the configuration of its snout, but the fossil was older by at least 30 million years than the oldest known tyrannosaur, and that animal, reported by Xu and Norell in 2004, was smaller than Guanlong. Nevertheless, a detailed numerical analysis of the data showed with 90 percent certainty that Guanlong was a tyrannosaur.