THE TRADITIONAL image of the dinosaur is -- extinct. That's the word from "Dinosaurs, Past and Present," at the Museum of Natural History.

This is a show of how artists, working with paleontologists, have depicted "the terrible lizards," and how new fossil discoveries have changed the picture. A companion show in the Rotunda gallery, "Dinosaurs, Mammoths and Cavemen: The Art of Charles R. Knight," is devoted to the work of the Old Master of this sort of thing, whose imaginative work in the first half of this century continues to be imitated.

Children of a certain age -- does every boy draw dinosaurs at age nine or 10? -- will find these two shows the highlight of their summer. And they're not without their rewards for the rest of us, with a little time to dig in.

Fossil detectives do make mistakes. One early blunder was made by paleontologist Richard Owen (who first suggested we call them Dinosauria) and sculptor Waterhouse Hawkins. They restored an iguanodon in the 1850s. Owen later published an apology, when he discovered that the horn on the end of the creature's nose was actually a "thumb spike," and belonged on its hand.

Perfectly understandable.

All along we've been thinking that dinosaurs had pea brains and that's why they're extinct. False. After all, they had to have something going for them to last 135 million years. What's more:

They didn't drag their tails.

They didn't all move slowly.

They weren't all cold-blooded.

They weren't all that ugly.

Today's informed artists no longer paint the single specimen: Dinosaurs were actually gregarious, with plant-eaters moving in herds and meat-eaters hunting in packs. Some even protected their young.

As William Stout shows in one of his paintings, hadrosaurs (duckbill dinos) had nurseries. Recent excavations in Montana uncovered massed fossils of eggs, hatchlings and juveniles. Stout also shows the prehistoric monster browsing daintily in a broadleaf forest; traditionally these plant-eaters have been illustrated swimming in swamps or lakes, munching on aquatic plants.

Deinonychus means "deadly claw," and the hotblooded deinonychus had two of them for slashing its prey. Discovered by John Ostrom in 1964, and drawn here by paleontologist Robert Bakker, this prehistoric animal had a bigger brain. That, along with its stereoscopic vision, suggests an efficient hunter to paleontologists. Dinosaurs could be quick and deadly. Similarly, the way the dryptosaurus did battle with its own kind could have been the origin of the expression "leapin' lizards."

One of Mark Hallett's many lively and clear illustrations is the "Awakening of Hunger" -- the yawning stretch of a duo of tyrannosaurus rex. Some scientists see them as fierce hunters. But others have thought about how skimpy the tyrannosaurus' forelimbs are and suggested that the king of the prehistoric beasts might have been nothing more than a giant scavenger. A dinosaur wimp.

Many questions are still puzzling those who enjoy speculating on the never fully knowable. Did the triceratops herd form a protective ring against predators? Did hadrosaurs cluster for warmth while sleeping? And, while we're at it, would humans have happened, if the big-brained dinosaurs had survived? DINOSAURS, PAST & PRESENT -- At the Museum of Natural History through August 31. DINOSAURS, MAMMOTHS & CAVEMEN: THE ART OF CHARLES R. KNIGHT -- In the Rotunda Gallery at the Museum of Natural History through August 31.