Otodus megalodon lived between 23 and 3.6 million years ago — Miocene through Pliocene. At somewhere between 40 and 60 feet and upward of 50 tons, it was the largest macropredatory shark that has ever existed.
Megalodon preyed primarily on large marine mammals including early whales, using serrated teeth to deliver devastating bites to prey too large to swallow whole. Recent research suggests it may have been regionally endothermic — maintaining a warmer body temperature than the surrounding water — which likely contributed to both its extraordinary size and its eventual extinction as ocean temperatures declined 3.6 million years ago.