'Megalodon' — a giant predatory shark that has inspired numerous documentaries, books and blockbuster movies — likely went extinct at least one million years earlier than previously thought, according to new research. This is a substantial adjustment as it means that O. megalodon likely went extinct long before a suite of strange seals, walruses, sea cows, porpoises, dolphins and whales all disappeared sometime about 1-2.5 million years ago.