• Paleontologists now classify dinosaurs in two main groups: "bird-hipped" and "lizard-hipped" according to the design of their skeletons. In lizard-hipped dinosaurs, the lower hip bones point in opposite directions; in bird-hipped creatures, the lower hip bones are long and thin and point backward. Both groups include dinosaurs that walked on two legs and dinosaurs that walked on all fours.

• The tail of the apatosaurus has 82 interlocking vertebrae bones. This dinosaur may have weighed as much as 33 tons.

• Maiasaura is known as the "good mother reptile." Females nested in groups. Their nests were 7-10 feet wide.

• Dryosaurus is a plant-eating dinosaur that is considered the gazelle of its time. At 10 feet in length, it could move rapidly.

• The Utahraptor may have been the deadliest dinosaur. It was a swift-running raptor with a huge claw on the middle toe of each foot.

• Ankylosaurus had a body covered with bony, oval plates set into thick, leathery skin. Rows of spikes covered the body and tail, acting like armor. Its tail could have been used as a club.

• Ceratosaurus had a fearsome appearance with a blade-like horn on its snout. This may have been used in head-butting battles with other males to win leadership of a group.

• Elasmosaurus lived in the sea and probably paddled along near the surface of the water. It was about 46 feet long, but more than half of its body length was a snakelike neck that could whip into the water to snap up fish.

Source: Ogden's George S. Eccles Dinosaur Park; "Simon & Schuster Children's Guide to Dinosaurs and Other Prehistoric Animals," by Philip Whitfield.