Askeptosauroidea is a superfamily of thalattosaurs, a Triassic group of marine reptiles. Askeptosauroidea is one of two major subgroups of Thalattosauria, the other being Thalattosauroidea. It include

Pachystropheus is a genus of prehistoric thalattosaurian marine reptile, from the Rhaetian of southwestern England and southern Germany. It is the youngest known thalattosaur.