Plesiosaurus

A plesiosaurus was an aquatic carnivorous dinosaur. They were commonly found in the depths of the Lake of Mists.

Description
Plesiosauruses had compact bodies and strong flippers that were used to swim. They had long and flexible necks that accounted for about a third of their length.

Behavior
Plesiosauruses were aggressive predators. They attacked any creature that crossed their path.