Megalodon is an extinct species of giant shark that lived from approximately 15 million years ago to 2 million years ago. It is believed to have resembled a stockier version of today's great white shark.
Megalodon, which likely grew to lengths of upwards of 50 feet, is regarded as one of the largest vertebrate predators ever to live. Its wide-ranging distribution in ancient oceans likely had a profound impact on the composition of marine ecosystems. The precise reason for megalodon's extinction is unknown, though it was likely a combination of cool oceans, a decline in food supply and increased competition from other large animals, primarily carnivorous whales.