Timing of dicynodont extinction in light of an unusual Late Triassic Polish fauna and Cuvier’s approach to extinction

Abstract

ABSTRACTDicynodont therapsids are prominent elements of Triassic continental faunas, but the date of their demise is controversial, linked either to end-Carnian faunal turnover or to end-Triassic mass extinction. The second timing is based on a unique, giant dicynodont-theropod dinosaur fauna from Lipie Śląskie, Poland, thought to be Rhaetian in age, due to conjectural botanical and conchostracan (but not tetrapod) evidence. On the other hand, an age assignment for the Lipie fauna to the mid-Norian (Revueltian) has been demonstrated recently by regional integrative stratigraphic data. To test once more this still debated age assignment, we recall the rationale of Georges Cuvier in the study of the fossil record (‘the best documents of Earth’s past are fossilized large tetrapods’). This approach was applied successfully 200 years ago to the species extinction dilemma. In light of the worldwide distribution of dicynodonts, the alleged compositional paradox of the ‘Rhaetian’ fauna from Poland can be significantly reduced by its recognition as a more ‘normal’ early-middle Norian assemblage. The simple megafaunal correlation appears to be conclusive. Thus, there was a major pulse of dicynodont extinction at the end of the Carnian, with the final extinction of the few remaining species happening in the Norian.