Pistosaurus was about 3 metres (10 ft) long, and had a body form resembling that of nothosaurs, aquatic reptiles that flourished during the Triassic. However, the vertebral column was stiff, like that of a plesiosaur, implying that the animal used its paddle-like flippers to propel itself through the water, as the plesiosaurs probably did. 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.
The following cladogram follows an analysis by Ketchum & Benson, 2011. Template:Clade