From the Miocene Period 20 million years ago to the Plio-Pleistocene Period 1.6 million years ago, the ancient seas were terrorized by the Megladon shark!  It is estimated that Megalodon could have easily reached 60 feet in length and weighed over 52 tons.  Some fossil teeth have been found that exceed 7 inches in length.  Megalodon shark lmost likely looked similar in appearance to a stocky Great White shark but about six times bigger!  Megalodon was the second largest predator that ever existed on this planet, the largest being the sperm whale.  Megalodon was larger and heavier than T. rex.