Megalodon (IMAGE) University of California - Los Angeles Caption Megalodons, which went extinct 3.6 million years ago, are believed to have grown to lengths of 50 feet. Credit Alex Boersma/PNAS Usage Restrictions Cite credit with use. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.