dinosaurs

Term 1: What is a dinosaur?
Definition 1: A type of reptile that dominated Earth for over 160 million years, during the Mesozoic Era.
Term 2: What are the two main groups of dinosaurs?
Definition 2: Saurischia (lizard-hipped) and Ornithischia (bird-hipped).
Term 3: When did the dinosaurs live?
Definition 3: From the late Triassic period (about 230 million years ago) to the end of the Cretaceous period (about 66 million years ago).
Term 4: What caused the extinction of the dinosaurs?
Definition 4: A large asteroid impact in the Yucatán Peninsula caused widespread environmental changes that led to their extinction.
Term 5: Are there any surviving dinosaurs today?
Definition 5: Yes, birds are considered to be the direct descendants of one line of theropod dinosaurs.