A three-ton Iguanodon named Aladar, who is raised from the egg by a clan of lemurs and eventually reunited with his own kind, finds himself and the other dinosaurs in trouble when flaming meteors devastate the landscape and the water supply diminishes. In a race against time, the dinosaurs attempt to reach the safety of their nesting grounds. When Aladar comes to the aid of a group of misfits unable to keep up with the breakneck pace of the herd, he makes an enemy of Kron, the stone-hearted leader of the group. Faced with such perils as treacherous rock slides and attacking Carnotaurs, Aladar and his friends must overcome tremendous obstacles before they can settle into a new life in a beautiful valley.