This book tells the story of Parasaurolophus, who lived 76 to 74 million years ago during the Cretaceous period. It belonged to a group called hadrosaurs, or duck-billed dinosaurs, named after their flat beak. Parasaurolophus had a long crest that swept back over its head. The crest was hollow, and Parasaurolophus probably used it to make deep honking sounds.