Plesiosaurus is a name given to a group of prehistoric marine reptiles that lived during the time of the dinosaurs, about 205 to 65 million years ago. They were not dinosaurs, but they lived in the same era. Plesiosaurus had a long neck and a large body, similar to the Loch Ness Monster and other lake monster legends. They had a unique body shape, with four flippers that they used to swim gracefully through the water.

Plesiosaurus had adaptations that allowed them to live in the ocean, such as streamlined bodies and powerful flippers. They were excellent swimmers and could move effortlessly through the water. Their long necks helped them catch prey, like fish and small marine animals. Plesiosaurus had sharp teeth to grab their food and swallow it whole.

Paleontologists have found fossil remains of Plesiosaurus all around the world. These fossils give us clues about how Plesiosaurus lived and evolved. By studying these fossils, scientists can learn about the ancient oceans and the creatures that lived in them.