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You're listening to ALL THINGS CONSIDERED from NPR News. The most famous of all the giant meat-eating predators that walked the Earth, that would be Tyrannosaurus Rex of course, actually they started out rather small, at least as dinosaurs go. That is evident from the latest fossil discovery from China, what's believed to be the earliest ancestor of T-Rex. The creature was a mere ten feet long and it sported a large crest on top of its head. NPR's Christopher Joyce introduces us to Guanlong, the crowned dragon.

CHRISTOPHER JOYCE, reporting:

It was just over a year ago when scientists announced they'd found the oldest ancestor of Tyrannosaurus Rex; a feathered dinosaur from China. Now scientists have discovered the bones of an even older ancestor. It was toothy to be sure, but about one fourth the size of T. Rex. And says lead scientist James Clark of George Washington University, it wasn't alone.

Dr. JAMES CLARK (Scientist, George Washington University): We have two skeletons preserved. The larger one lying on top of the smaller one. Their ages are seven and 12 old. As far as its distance from Tyrannosaurus, it's actually more than 90 million years older than Tyrannosaurus Rex.

JOYCE: Finding the Adam or Eve of the T. Rex family is remarkable enough. But finding two of them, one on top of the other, is as, one team member described it, weird. How that happened no one knows. There is no sign of a struggle and their deaths were probably years apart. Guanlong looks something like a smaller, more graceful T. Rex. Steak-knife-like teeth, but with longish arms instead of the short rather pathetic arms of T. Rex. It had three fingers like modern birds, and might have had fathers, says Clark, though he didn't find any.

Guanlong suggests that nature stuck to a basic design that worked for predators. But this discovery suggests that over time evolution apparently favored living large. Team member Gregory Erickson is with Florida State University.

Dr. GREGORY ERICKSON (Florida State University): Maybe it's just a case of these animals sort of, you know, tracking larger prey. You know, if, kind of an arms race could be going on here. As herbivores get larger then it makes a niche for a larger predator.

JOYCE: Another mystery about this creature, it had something unique to tyrannosaurs, a large crest on its head like the crest many birds have but bony inside. Tom Holtz, a dinosaur scientist at the University of Maryland, says lots of dinosaurs are believed to have display ornamentation plates along the back, or bony frills around the neck for example.

Dr. TOM HOLTZ (Dinosaur Scientist, University of Maryland): You know, if you have a big showy display structure at least in certain seasons, you've got a lot of color on it to say, you know, hi look at me, I'm ready for breeding, or hey stay away from me I'm dangerous.

JOYCE: Scientists say the past decade of dinosaur discoveries, especially in China, has revealed a menagerie of tyrannosaur ancestors. Smaller, quicker, feathered, and now crested. And they were by no means top dog when they started out in the Jurassic Period, some 180 million years ago.

Dr. HOLTZ: In the cast of the tyrannosauroids, we see they spent a long period of their history as secondary predators, as minor components in the predatory guilds. And it's only at the very end, only the last 15 million years of the Cretaceous, really, that they take off as the top. So, this helps reinforce the idea that the tyrannosaurs that we know and love, the great T. Rex, was, in a sense, a really late experiment.

JOYCE: An experiment that came to a screeching halt, fortunately for we mammals, 65 million years ago with the great dinosaur extinction. The new discovery is described and illustrated in the most recent issue of the journal Nature. Christopher Joyce, NPR News.

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