The gorgons ruled the world of animals long before there was any age of dinosaurs. They were the T. Rex of their day until an environmental cataclysm 250 million years ago annihilated them - along with 90 percent of all plant and animal species on the planet - in an event so terrible even the extinction of the dinosaurs pales in comparison. For more than a decade, Peter Ward and his colleagues have been searching in South Africa's Karoo Desert for clues to this world: What were these animals like? How did they live and, more importantly, how did they die?