The Megalodon Shark was the biggest predatory shark to ever live. Reaching lengths of 60 feet or more, these monstrous sharks ruled the oceans for more than 15 million years. They were so large they fed on whales. Some believe the megalodon shark could still live in the depths of the oceans, but most scientists agree that megalodon went extinct about a million years ago. Why is a mystery, but some possible explanations are climate change, changes in its primary food source, and competition for food from rivals such as killer whales and the modern great white shark. The name Carcharodon megalodon has been replaced by Carcharocles megalodon, because paleontologists belive that the modern great white, Carcharodon carcharias is more closely related to an extinct species of Mako shark than to Megalodon.