Plesiosaurs had a couple of different body shapes that affected what their necks and heads looked like, but they all had some shared body traits. This is Meyerasaurus (MY-er-uh-sor-us), a plesiosaur that left behind an almost complete skeleton for scientists to study.
Plesiosaurs had four flippers. They most likely used their front flippers to move and their back flippers to steer, much the way a sea turtle swims.
Scientists aren’t exactly sure how plesiosaurs used their tails. It is possible some plesiosaurs had tail fins, similar to a fish, but it is unlikely that plesiosaurs used their tails to move.
Some plesiosaurs had long necks with small heads. Others, called pliosaurs, had short necks with large heads, like crocodiles.
Meyerasaurus had a small head. Kronosaurus is an example of a pliosaur with a head like a crocodile. Plesiosaurs and pliosaurs had sharp teeth used to catch and hold onto prey such as fish.
Plesiosaurs had lungs and breathed air. Their lungs were probably small. Big lungs full of air would have made plesiosaurs float and made it hard to swim and dive. Small lungs meant they could move underwater better but had to come up for air more often.