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A Dino King's Ancestor

Researchers have unearthed remains of the oldest known dinosaur of the tyrannosaur family.

Tyrannosaurus rex gets a lot of attention for being one of the fiercest large dinosaurs that ever lived. These fearsome meat eaters, however, weren't the first of their kind.

In northwestern China, paleontologists have found remains of Guanlong wucaii, the oldest known dinosaur that belongs to the tyrannosaur family. The name means "crowned dragon from the five-colored rocks," and the species lived about 160 million years ago.

This dinosaur, the oldest known species in the tyrannosaur family, had a 6-centimeter-tall crest that ran along the top of its snout.

This dinosaur, the oldest known species in the tyrannosaur family, had a 6-centimeter-tall crest that ran along the top of its snout.

Zhongda Zhang/Institute of Vertebrate Paleontology & Paleoanthropology (IVPP), Beijing

G. wucaii were only 3 meters (9.8 feet) long, but they were probably ancestors of the much larger T. rex, which lived 95 million years later, researchers say.

In China, the researchers found two G. wucaii skeletons that were nearly complete. One appeared to be a 12-year-old adult. The other was a 6-year-old youngster. Each one had a hollow, bony crest running along the top of its snout.

The skull of this dinosaur had a hollow, bony crest running along the top of its snout.

The skull of this dinosaur had a hollow, bony crest running along the top of its snout.

IVPP

The crest, which was 6 centimeters (2.4 inches) tall on the adult (and smaller on the juvenile), baffles scientists. The crest wasn't connected to the creature's nose. Nor did it appear to be useful for fighting. Instead, it's possible that the structure served as a sign of adulthood or a way for the animals to tell the difference between males and females. It could have also helped them recognize members of their own species.

The new fossils shed light on debates about tyrannosaur evolution. Paleontologists used to think that T. rex and its cousins evolved from huge predators that lived 145 million years ago. Now, it appears that tyrannosaurs evolved much earlier than that, from a group of small, meat-eating dinos called coelurosaurs.

This drawing shows what a complete skull, with crest, probably looked like.

This drawing shows what a complete skull, with crest, probably looked like.

R.S. Li/IVPP

G. wucaii fit somewhere in the middle, sharing traits with both groups. It had tyrannosaur-like teeth in the front of its jaws and nasal bones that were fused together to strengthen its skull. But it also had the coelurosaur's long snout, bladelike teeth on the sides of its jaws, and long arms with three-fingered hands that could grasp objects.

Also unlike T. rex, G. wucaii had to hold its own in a harsh world. During its time on the planet, it faced predators twice its size.—E. Sohn

Going Deeper:

Perkins, Sid. 2006. Ancestor of kings: Early progenitor of T. rex had a crest. Science News 169(Feb. 11):83. Available at http://www.sciencenews.org/articles/20060211/fob1.asp .

For additional information about the discovery of remains of Guanlong wucaii, go to www.gwu.edu/~newsctr/fossilfind/ (George Washington University).

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