The mosasaur was a cretaceous lizard and lived in the oceans of the world. Some believe they may have also lived in fresh water. It had a powerful, crocodile like body that grew up to 30 ft in length. It had large well adapted paddles that made it a good swimmer. The mosasaur teeth and bones are found today in various locations worldwide. Those specimens are approximately 65 - 135 million years old.