Tyrannosaurus Tiny

FORGET ABOUT WHETHER AN ERRANT COMET, ANGRY volcano or invidious virus killed the dinosaurs 65 million years ago. Scientists have still not explained how the Saurian dynasty got started or why it dominated the earth for more than 150 million years. The discovery in northwestern Argentina of the fossilized skeleton of a 10-kg (22-lb.) carnivore that is 230 million years old may help paleontologists begin to solve the mystery. In the British journal Nature, researchers from the University of Chicago and the National University of San Juan, Argentina, report that the dog-size predator is the most primitive dinosaur ever found.

Although the ancient hunter lacked the flexible lower jaw and other advanced features of its more ferocious descendants, the overall shape and internal structure of its bones provide strong evidence that the beast was a true dinosaur. "This fossil confirms our suspicions that dinosaurs began as small, carnivorous, bipedal animals," says Paul Sereno, an assistant professor of anatomy at Chicago and a leader of the expedition. "We are just a couple of steps away from the ancestor of all dinosaurs." The scientists named the find Eoraptor, or "dawn stealer," because it appeared at the dawn of the dinosaurs and, considering its modest size, probably used stealth rather than brute force to snatch small prey.