Preservation of exceptional vertebrate assemblages in Middle Permian fluviolacustrine mudstones of Kotel'nich, Russia: stratigraphy, sedimentology, and taphonomy

► The outstanding Late Permian tetrapod site Kotel'nich in Russia is described. ► The preservation of complete skeletons of the pareiasaur Deltavyatia is a mystery. ► Skeletons occur in scours on a palaeosol, one per scour and apparently standing. ► The pits may have been eroded or dug as wallows, but the skeletons were washed in. ► Floodplain dynamics meant complete skeletons could only be preserved in scours.