About 20 million years before the appearance of the first dinosaurs, the biggest extinction the world had ever known had occurred. Over 90% of all plant and animal species thenalive on land and in the sea had died out. There are two main types of dinosaurs, named from the configurationof their pelvic bones: bird-hipped and lizard-hipped.In the Early Jurassic, dinosaursstarted getting larger. Diplodocuswas over 30 meters long - but even he wasn‘t safe from predators.