(4) reptiles that became extinct Explanation: Although the word dinosaur means "terrible lizard," the name is somewhat misleading, as dinosaurs are not lizards. Rather, they represent a separate group of reptiles with a distinct upright posture not found in lizards, and many extinct forms did not exhibit traditional reptilian characteristics. Through the first half of the 20th century, before birds were recognized to be dinosaurs, most of the scientific community believed dinosaurs to be sluggish and cold-blooded.