Plesiosaurs were not a real dinosaur! They are in fact marine reptiles which can be divided into two groups: The long necks, and the short necks. Much like modern-day sea turtles, they breathed air and therefore would likely have laid their eggs on beaches before returning to the oceans.
Did you know?
Plesiosaurs could reach lengths of up to 5 metres and weigh up to 450 kilograms.