Eoplesiosaurus, a now-extinct genus of basal plesiosauroid, existed during the Early Jurassic period, specifically during the probable earliest Hettangian stage, in the United Kingdom. This genus is represented by a sole species, E. antiquior.

The limited fossil record of Eoplesiosaurus makes it challenging to fully understand its paleobiology and behavior. However, its classification as a plesiosaur offers some insights into its possible lifestyle.

Plesiosaurs like Eoplesiosaurus are thought to have been relatively slow swimmers, relying on ambush tactics to catch their prey. They might have employed their long necks to snatch fish and cephalopods by surprise, using their sharp teeth to secure their catch.

Evidence from other plesiosaur species suggests that they could have been social animals, living and hunting in groups. It is plausible that Eoplesiosaurus displayed similar social behavior, further enhancing its chances of survival in the ancient seas.

As a marine reptile, Eoplesiosaurus was well-adapted for a life in the water. Its streamlined body and paddle-like flippers allowed it to maneuver through the oceans with ease. Being carnivorous, it likely fed on fish and cephalopods, using its sharp teeth to grasp and consume its prey.