Spanning just 10 feet in length and sporting a tiny horn on its nose, a newly identified dinosaur has become the oldest known relative of the fierce meat-eater, Tyrannosaurus rex. The discovery suggests such tyrannosaurs were quite petite before they evolved into giant killing machines just before their demise.

The dinosaur, called Proceratosaurus, lived some 170 million years ago. "We can say conclusively it's the earliest representative of the line of evolution that led to Tyrannosaurus,"