WASHINGTON – 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.
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.
The team 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.
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 7 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 6 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 in 2004, was smaller than Guanlong. Nevertheless, a detailed numerical analysis of the data showed with 90 percent certainty that Guanlong was a tyrannosaur.
Team member David Eberth of Canada’s Royal Tyrell Museum said the Junggar Basin during Guanlong’s time was a marshy, subtropical wetland, rife with rivers and lakes, far different from today’s austere wilderness.
Clark said the team has found larger predators in the area, but that Guanlong was probably a fleet hunter well able to take care of itself in a hostile environment.
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