A cool and misty dawn, circa 78 million B.C. A lone triceratops interrupts a leisurely meal of ferns and twigs to glance around uneasily. Though the 11-ton creature is an intellectual lightweight, it senses the danger lurking in the surrounding forest. Suddenly, out from behind a tree lumbers one of the largest and fiercest carnivores that have ever lived: Tyrannosaurus rex. Although this beast is a mere adolescent, it is 15 ft. tall and armed with dagger-sharp teeth. The triceratops attempts a retreat, but the cold-blooded creature can only move slowly. It is too soon after sunrise, and the dinosaur hasn't had time to absorb the heat it needs to rouse its sluggish metabolism. While T. rex has the same problem, its longer legs enable it to quickly overtake the docile herbivore. And then . . .
Wait! Time out! There is something wrong with this picture. Nearly everything, in fact. Two decades ago, paleontologists might have signed off on such a scenario, but not today. An avalanche of new evidence -- from fossilized bones, dinosaur nests, eggs and even footprints, analyzed with such high-tech equipment as CAT scans and computers -- has completely transformed scientific thinking about dinosaurs. Triceratops and other herbivores were not necessarily dull-witted, nor did they wander around alone; they probably traveled in vast herds and went on annual migrations. They may have cared for their young, and perhaps cooperated with one another to protect them from predators. Predators too were social. All but the oldest and biggest tyrannosaurs traveled in packs and attacked like prowling wolves, as did most of the smaller and nastier predators. (Despite popular belief, Tyrannosaurus was not necessarily the most vicious.)
Dinosaurs probably weren't cold-blooded either. They could move along briskly, even in cool weather; some lived above the Arctic Circle, where the sun never rises in winter. Rather than a uniform dull green, they could easily have been striped, spotted and brilliantly colored. Even the idea that all the dinosaurs died out 65 million years ago is now passe. Many experts believe that one resilient line is still flourishing today. The common name for these modern dinosaurs: birds. Observes Mark Norell, a paleontologist at the American Museum of Natural History in New York City: "Birds are more closely related to Tyrannosaurus rex than Tyrannosaurus is to almost any dinosaur you've ever heard of."
This rewriting of conventional wisdom has accelerated in the past 10 years. New fossil beds have been found and old ones rediscovered in the Gobi Desert, along the ancient Silk Road in the mountains of China, on the margin of the Argentine Andes and in the jungles of Laos and Thailand. Despite the remarkably small number of scientists working in the field -- only about 100 worldwide, splitting a meager $1 million in research funds -- a new dinosaur species is found on average every seven weeks.
Surprises crop up constantly. The latest: a new species from Mongolia, announced last week by Norell and several U.S. and Mongolian scientists. Known as Mononychus (meaning one claw), the turkey-size animal looked like a modern, flightless bird, complete with feathers, but had bone structures characteristic of both birds and dinosaurs. Its discovery cements the bird- dinosaur link even more firmly.