Are birds dinosaurs? Did dinosaurs walk on two legs or four? How did the Jurassic Period shape the world today? Learn all this and more in The Jurassic Period! Go back in time 200 million years and find out how the dinosaurs lived. Level 1 readers are aimed at children who are starting to recognize common words and are capable of sounding out unfamiliar words. Short, simple sentences help guide the reader through new concepts and ideas.