Albertosaurus:
Albertosaurus stood on two muscle-bound legs, ate gobs of meat, had oversized toothy jaws, and sported sharp claws on the ends of its legs and arms. Thirty feet long and nearly 6,000 pounds when full-grown, Albertosaurus hunted at least occasionally, preferring hadrosaurs and other plant-eaters, but there is some debate about whether it was primarily a hunter or a scavenger.
Hadrosaurus:
A bulky, cheeky, duck-billed plant-eater whose nearly 1,000 teeth ground up plant matter with efficiency, Hadrosaurus played a pivotal role in the early days of the human study of dinosaurs. The discovery in 1858 of a nearly complete Hadrosaurus skeleton in a New Jersey marl pit was the first semi-complete dinosaur skeleton ever found, jump-starting the science of paleontology. With a long tail and thick midsection, the Hadrosaurus may have grown to be about 32 feet long.
Theropods:
Lived throughout the reign of the dinosaurs, from about 230 million-65 million years ago.
The carnivorous, two-legged dinosaurs called theropods included Tyrannosaurus, Allosaurus, Albertosaurus and Ceratosaurus: all big and fierce with lots of dagger-like teeth. Smaller theropods included Dromaeosaurus, Deinonychus and Velociraptor, which sometimes attacked much larger dinosaurs in packs and relied on sharp claws and speed.
Ornithschians:
Lived throughout the reign of the dinosaurs, from about 230 million-65 million years ago.
A plant-eating family composed mainly of relatively small, beaked dinosaurs, some ornithischians, like Dryosaurus and Hypsilophodon, used swiftness and nimbleness to survive. Others were bulky and sported a dazzling variety of spikes and armor that made them nearly invincible unless surprised. Triceratops, Stegosaurus and Ankylosaurus fit this description
