These were marine reptiles that were very successful sea hunters in the Jurassic. An example of these creatures is the Ophthalmosaurus3. They breathed through the lungs and had to constantly come to surface of the sea to breathe. They gave birth to young pups and practiced territoriality besides having toothless mouths. They fed on fish and molluscs that were in the sea3. One particular feature is their ability to feed at night as they had big eyes that were sensitive to light. They were predated by sharks especially during the laborious birth but could hide in the corals. This was also a feature that the young also used to escape predators. They propelled themselves using the powerful tails and dolphin-like flippers on their side which they used to steer themselves3.
Sharks and rays and crocodiles were the other known marine animals living in the Jurassic era. Some were predators yet others were prey for the marine reptiles.