At Panxian, there appears to have been a transition in the endemic marine reptile fauna, possibly caused by volcanism. This volcanism is indicated by the presence of a bentonite layer between the Middle and Upper Reptile Horizons. From lower in the Upper Reptile Horizon, fossils have also been found of the ubiquitous mixosaurian ichthyosaur "Mixosaurus panxianensis" (which occurs in all layers), the pachypleurosaurs "Keichousaurus sp." and "Wumengosaurus delicatomandibularis", and fish, although fossils of the latter are fragmentary. The lower Middle and Lower Reptile Horizons also include the mixosaurian "Phalarodon cf. fraasi", the primitive ichthyosaur "Xinminosaurus catactes", the placodont "Placodus inexpectatus", the nothosaurs "Lariosaurus hongguoensis" and "Nothosaurus yangjuanensis", and the archosaur "Qianosuchus mixtus", alongside bivalves and saurichthyid fish.