10 Biggest Sea Dinosaurs That Ever Existed On Earth

8. Nothasaurus

Vicious Hunters of the Ancient Seas The Nothasaurus, living approximately 230 million years ago, may not have been among the largest prehistoric sea creatures, but they were certainly among the most vicious. These reptiles, measuring around 15 feet in length, had long, needle-sharp teeth that they used to catch squid and fish. Interestingly, Nothasaurus shared several similarities with modern sea lions, including the ability to walk on land and potentially give birth to their young.