Megalodon is an extinct species of giant shark that were around in the Cenozoic Era (28 Million years ago). The reached massive sizes of up to 67 feet. They prayed on dolphins, sea turtles, and even large sperm whales. Megaldon was the most formidable carnivor to ever live. It is not know exactly why Megalodon went extinct but some seggestions say that it never went extinct, but only changed in size after a depletion of rich oxygen in the ocean.