Nothosaurs and the plesiosaur connection
The plesiosaurs were far better adapted for aquatic life than their relatives the nothosaurs. Their bodies were flat and rigid, and they were powered by paddles that worked with a flying action, rather like modern turtles. In Triassic times there were many that seem to be transitional between the two groups.
The pistosaurs seem to have been intermediate between the nothosaurs and the true plesiosaurs. Their remains are known from both sides of the Atlantic, Pistosaurus was found in Germany, while its relative Augustasaurus was found in America. It is not known whether they swam like crocodiles as nothosaurs did, or like turtles like plesiosaurs.
Features: Theintermediate nature of this animal is shown by the nothosaur-like body and the plesiosaur-like head. The plesiosaur skull still had the palate of a nothosaur, while the largely nothosaur body had the stiff backbone that usually denotes a plesiosaur. The teeth are similar to both, and the animal was obviously an active fish- hunter as both groups were. Hence there is an ongoing discussion among scientists of the actual classification of this animal.