Much of what you thought you knew about dinosaurs turns out to be wrong. That's the take-home message from Dinosaurs: Ancient Fossils, New Discoveries, which opened Saturday at the American Museum of Natural History in New York City.

Recent finds and technologies have revolutionized scientists' understanding of dinosaur biology, behavior and even extinction. In one especially well executed display, an animatronic T. rex moves surprisingly sluggishly, minding what researchers now believe was the animal's speed limit of 11 to 16 kilometers an hour--a striking contrast to the car-chasing pace of Jurassic Park's monster. It turns out T. rex was far too massive to be a swift stalker.

Across the way, a 60-foot-long steel-and-fiberglass model of an Apatosaurus skeleton and accompanying video lay to rest another popular notion of dinosaur biomechanics--namely, that the long-necked herbivores could hold their heads high. Computer analyses indicate that the beasts were largely limited to horizontal neck movements.

Other displays examine what footprints can reveal about dinosaur social structure, the relationship between dinosaurs and living birds and the events that brought the Age of Dinosaurs to an abrupt close. And a rogues gallery of skulls from creatures including Triceratops and Stegosaurus discusses the latest thinking on what purpose their elaborate horns, frills and other adornments really served.

The crown jewel of the exhibition is the 700-square-foot diorama of a forest that existed in China's Liaoning Province 130 million years ago. Widely recognized as one of the most important paleontological sites in the world, Liaoning has yielded exquisitely well preserved remains of organisms ranging from flowering plants to feathered dinosaurs. Many are represented here. Repenomamus giganticus, the largest Mesozoic mammal on record, hunts baby psittacosaurs; Microraptor gui, a four-winged dinosaur, glides between trees; Peipiaosteus pani, a close relative of the modern day sturgeon, swims in a pond under the watchful eyes of waterstriders and dragonflies.

The exhibit, organized by the AMNH in collaboration with the Houston Museum of Natural Science, the California Academy of Sciences in San Francisco, Chicago's Field Museum and the North Carolina Museum of Natural Sciences in Raleigh, will remain on view in New York until January 2006, after which it will travel to the partner institutions.Tickets, which include general admission, are $19 for adults, $14 for students and seniors and $11 for children.