A clade of saurischian (‘lizard-hipped’) dinosaurs whose descendants include the modern birds. It comprised bipedal carnivores, including Tyrannosaurus rex, which was over 12 m long and 4.5 m tall. Shared traits included hollow, thin-walled bones, three extended clawed digits on both the hands and feet, and a furcula (‘wishbone’). Some fossil theropods had feathers very similar to those of modern birds, including Archaeopteryx, which lived about 150 million years ago.