The early Jurassic period was not just a time when giant reptiles roamed the land. They also swam in the prehistoric seas. Plesiosaurus, with its long, thin neck and paddle-like limbs, was one of the large marine reptiles that lived at this time. Full-color images and interesting, accessible text will help students find out more about what life might have been like for this underwater creature that could grow to a whopping 16 feet in length.