The nothosaur Eupodosaurus, initially classified as a stegosaurian dinosaur, is now considered synonymous with Lariosaurus.
For a nothosaur, Lariosaurus was primitive, possessing a short neck and small flippers in comparison to its relatives. This would have made it a relatively poor swimmer, and it is presumed to have spent lots of time on dry land, or hunting in shallows.
Lariosaurus unique among nothosaurs because its front legs were adapted into paddles, while the back legs remained five-toed. Further, based on skeletal findings of immature lariosaurs inside the adults, Lariosaurus is believed by many to be viviparous, or able to bear live young. Another Lariosaurus skeleton was found with two juvenile placodonts of the Cyamodus genus in its stomach, giving an indication of its diet.