Dinosaur dreams.

Early one summer morning, Dr. Nicholas Hotton, who is a research curator in the Smithsonian's department of paleobiology, goes out into the woods by his house in Takoma Park.

"I was batting around trying to look at an animal I'd just glimpsed -- it was like a springbok, the part I could see. And then I saw the rest of it. It wasn't all that big, but it had a long reptilian tail and a great big neck with a little bitty head. The neck and head were electric blue. I knew it was a dinosaur. I said, 'My God, what's a dinosaur doing in Takoma Park?' "

He recalls this dream while standing amid the hammering and scaffolding of last-minute adjustments to the Smithsonian's new dinosaur hall, which opens, and not a moment too soon, to the public today in the Museum of Natural History.

"Whenever I dream about dinosaurs I dream about live ones, not the bones," he says.

Who doesn't? That's why the star of the new hall is the pterosaur floating over the tons of bones, the Jurassic xylophones, the Mesozoic picket fences that are mere skeletons of diplodocus, stegosaurus, camarasaurus and so on. The pterosaur is a replica, not a skeleton. It is a scientist's dream of what it looked like, which was nothing but hungry with 40-foot wings of brown, translucent skin; or a carnivorous first baseman's mitt, or a bird-of-paradise flower that just walked out of a leather bar.

"I think it could maneuver on the surface of the water," says Hotton. "It would move those wings back, like an Englishman tucking an umbrella under his arm, and then raise them to catch the wind like lateen sails. You wheel around to face the wind and the swell. Pap! Up go the wings and off you go."

Dreaming.

We need dinosaurs.

We started discovering their bones in the late 18th century, just as the age of reason and the Enlightenment and all that banished the unicorn, the camelopard, the basilisk and all that from our taxonomies and our psyches. In 1824 the British, who had always been so perceptive with dragons (St. George and all), gave us the first drawings the bones implied. In 1841 the British anatomist Sir Richard Owen gave us the word "dinosaur," meaning "terrible lizard." Since then, explorers have found dinosaur remains everywhere from the Canadian Yukon to Mongolia to Tanzania to Australia.

There were giants in the earth in those days -- Genesis.

A land of giants; giants dwelt therein in old time; and the Ammonites call them Zamzummin -- Deuteronomy.

If you don't think 20th-century humans need dinosaurs, you don't have children.

"I talked to children from preschool through first grade," says William Schowalter, a pediatric psychiatrist at Yale's Child Study Center. "In any given class there will be two or three children who know more about dinosaurs than they know about their classmates. They have no psychiatric diagnosis. It gives them a good feeling about themselves to know something in an adult area, and they're identifying with the largest creatures who ever walked the earth -- and the most ferocious. The children divided them into meat- and vegetable-eating categories. The meat eaters are seen as male, especially tyrannosaurus rex -- it's ferocious, and dangerous, and children can take on its attributes in a kind of animistic way. The vegetable eaters are seen as female, and benevolent.

"I'd ask these kids about superheroes, and why they weren't more fascinated with them. The difference is that the dinosaurs were real at one time, so there's a lovely ambiguity -- they're real, but they're gone, so the children don't have to fear them. Every class has a Batman and a Spiderman clique, but these come and go. Dinosaurs last."

Check out the 12-minute movie in the dinosaur hall, a collection of great movie dinosaur sequences starting with the animated -- as opposed to moving-model -- "Gertie on Tour" in 1909. Gertie, a lovable brontosaurus, plays with a trolley car. The most intriguing sequence is from "King Kong" -- as if you didn't already know that. The explorers stampede screaming through a swamp while a dinosaur chases them; civilization pursued by the Ur-beast, the ego in flight from the id.

"Dinosaurs bring up the kid in all of us," says Byron Preiss, editor of a brilliantly illustrated $12.95 paperback from Bantam Books entitled "The Dinosaurs -- A Fantastic New View of a Lost Era." He adds: "People aren't embarrassed to be fascinated with them because they're scientific."

Peering around a construction workers' barricade at the Smithsonian, Jennifer Regan Sparks, 6 years old and of Toledo, is asked if dinosaurs were mean.

"No," she says, then spots an exception across the way, a great horned thing with a huge shield of bone over its shoulders, the sort of beast that would make you turn to a rhinoceros for sympathy.

"Triceratops was mean," she says.

She would not like to travel back in time to see dinosaurs. " 'Cause we're scared of 'em."

Says Brian Sparks, 3: "My dad isn't!"

Scientists have identified 250 kinds of dinosaurs since the boom began in the last century. They had heights from two feet (i.e. syntarsus) to 50 feet (ultrasaurus). They weighed from one pound (baby psittacosaurus) to 200,000 pounds (brachiosaurus or ultrasaurus).

Generally, they ran big, by current standards. Like elephants. Giants in the earth.

Nobody's sure why the last of them died, 63 million years ago. There's no shortage of explanations: The world got too hot. Or too cold. A supernova killed them with radiation. An asteroid hit the earth and covered the sun with dust. Their bodies were too big for their brains. The oceans shrank. Their eggs went soft. Who knows? Maybe they got disgusted, looking around seeing shrews and proto-rats scurrying through the swamps, and said: Mammals? If this is the future, include us out.

What we know for sure is that they were the ancients, the Old Ones, the precursors.

It would be lovely to think that whatever is here 63 million years after we're extinct will remember us with the love and fascination we give dinosaurs. Maybe if a tremor of doubt says it isn't likely, think of what that says about dinosaurs.

No wonder we care.