Pistosaurus

Pistosaurus is a genus of marine sauropterygian reptiles. It is a Nothosaur, a relative of the plesiosaurs.
"Pistosaurus" was a advanced nothosaur-like body with a plesiosaur-like head. Is presently known only from the Middle Triassic. Even if it is a nothosaur it is acknowledged to be closely related to the ancestors of plesiosaurs.
The head also resembled that of a plesiosaur, but with the primitive palate of a nothosaur, and numerous, sharp teeth ideal for catching and eating fish.
Although it is unlikely that "Pistosaurus" was a direct ancestor of the plesiosaurs, the mixture of features suggests that it was closely related to that group.