Tyrannosaurus rex

Given its 6-ton body, 4-foot jaw, and dagger-like teeth, no wonder paleontologists named this dinosaur "tyrant lizard king." T. rex was one of the largest carnivores (meat-eaters) ever. Like other theropod dinosaurs, T. rex walked on two legs and used its tail for balance.

Image credits: main image, Rick Spears; story, tyrannosaurus standing courtesy of AMNH; quote, Mark Norell courtesy of Discovery Channel Online.