Birds are dinosaurs because they descended from the first theropod and the first dinosaur. A 3-toed hind foot was an adaptation from moving rapidly and catching prey. The 3-toed of meat-eaters such as Tyrannosaurus has survived as the 3-toed foot in birds. The elongated arm bones that support the wing evolved in the first coelurosaur. An Apatosaurus and tyrannosaurus rex are extremely different from each other. An Apatosaurus lived in the Late Jurassic, while a tyrannosaurus lived in the Late Cretaceous. An Apatosaurus was an Herbivorous; while a tyrannosaurus was a carnivorous. An Apatosaurus was also almost twice of a Tyrannosaurus’ size.
4. The Ornithischian dinosaur, or "bird-hipped" dinosaurs, and the Saurischian dinosaur, or "lizard-hipped" dinosaurs. The most visible difference between the two types of hip is the orientation of the pubis. There is evidence that a large asteroid or comet struck the earth causing the end of the Age of Dinosaurs. Dinosaurs were unable to survive through the altered temperatures, reduced sunlight, generated acid rain, or major volcanic