sentences:  Its brother species the "Pteranodon" became hermit-like and remained below the canyons as a guardian of the World Beneath.Thousands of years ago, the advanced city of Poseidos was plotting to take over the rest of Dinotopia.One boy, Gideon Altaire, who loved the forbidden mainland, defied the law and stole the Ruby Sunstone from the Air Scorpion, a new vessel built for conquest, cutting off the machine's source of power.