THE TRICERATOPS paws the Mesozoic landscape, lowers its three-horned head and fixes a stern eye on you while it emits a threatening bellow. The effect is startling. You know the dinosaur isn't real, but it's just real enough to make one pause and wonder at the remarkable exhibit "The Dinosaurs Live Again" at the Maryland Science Center in Baltimore.

Six large-scale model dinosaurs are the stars of an exhibit of films, fossils and other dinosaur memorabilia. The dinosaurs are computer-controlled creatures, stuffed with air-driven valves that move eyes, open mouths, lift legs, turn heads and twitch tails in a dimly lit setting of plants and rocks meant to resemble a prehistoric playground. Surprisingly, the oversized puppets are effective, and if two visits are any indicator, adults might be more captivated by them than children.

"The Dinosaurs," drawing large crowds since its opening late last month, is the sequel to the Maryland Science Center's popular 1987 exhibit "Return of the Dinosaurs." It also is one of three new shows at the center. "To Fly," the long-running cinema staple of the National Air and Space Museum, is now being presented in the center's new IMAX Theater. In its Davis Planetarium, "Starwatch '88" shows the wonders of the night sky and offers tips on locating planets, stars and constellations.

Across the Inner Harbor, in the Tropical Rain Forest at the National Aquarium, the exhibit "Hidden Life" explores the wonder of animals' ability to hide in plain sight. The seven displays require viewers to take the time not only to look, but to see. A large, bright green leaf over a limb becomes an emerald tree boa, a squashed fungus hidden under a plant leaf suddenly moves and turns into a matamata turtle.

THE DINOSAURS LIVE AGAIN

at the Maryland Science Center through February 29. The center is open 10 to 5 weekdays, 10 to 6 Saturdays and noon to 6 Sundays. Admission. 601 Light Street, Baltimore. 301/685-2370.

HIDDEN LIFE

at the National Aquarium in Baltimore. The aquarium is open 10 to 5 Saturday through Thursday, 10 to 8 Fridays. Admission $6.75 adults, $5 students 12 to 18 and senior citizens, $3.75 children 3 to 11. 501 East Pratt Street, Baltimore. 301/576-3860.