Plesiosaurus was strictly a marine creature from the Sauropsida subcategory, although a study by William Conybeare made the claim that it was more of a reptile than a mammal. The Plesiosaurus and the Ichthyosaurus have been found in the same area of the Lias of England and Germany. It was first discovered by Mary Anning in 1821. It is known from several almost complete skeletons found over the years.
What did they eat?
Since they lived in the sea they would mostly survive by taking in and consuming fish of all sizes or any other swimming animal in the ocean during that time period, due to their sharp teeth and incredibly strong jaws. It is even said to have eaten mollusks that lived along the prehistoric shoreline.
Studies show that the Plesiosaurus lived and behaved much like the present-day sea turtle. For the majority of their life, they lived in the water but would come to shore to lay their eggs as sea turtles do.
The most fascinating thing about Plesiosaurus is the fact that they looked like a combination of the characteristics of many animals. This included the serpent, a fish, a dinosaur and a turtle. The Plesiosaurus had necks that were like that of a snake. Long and serpent-like not to forget their small heads. The vertebrae of the animal were flat-ended which means that it seemed to be very stiff-necked. They would grow to a length of 11 feet. Their turtle-like bodies with two pairs of paddles on either side enabled them to navigate the waters. The Jaw of the Plesiosaurus was able to open very wide and had a lot of conical teeth that were in sockets