(suborder Theropoda) Large carnivorous saurischian (lizard-hipped) dinosaurs of the of the Jurassic and Cretaceous Periods (about 200 to 65 million years ago). They walked on their two back feet, and most had large jaws and short "arms". Tyrannosaurus rex is a well-known example of a theropod. [ More information] Artist's rendering of theropod.