The Permian–Triassic mass extinction: Ostracods (Crustacea) and microbialites

The end-Permian mass extinction (EPE), about 252 Myr ago, eradicated more than 90% of marine species. Following this event, microbial formations colonised the space left vacant after extinction of skeletonised metazoans. These post-extinction microbialites dominated shallow marine environments and were usually considered as devoid of associated fauna. Recently, several fossil groups were discovered together with these deposits and allow discussing the palaeoenvironmental conditions following the EPE. At the very base of the Triassic, abundant Ostracods (Crustacea) are systematically present, only in association with microbialites. Bacterial communities building the microbial mats should have served as an unlimited food supply. Photosynthetic cyanobacteria may also have locally provided oxygen to the supposedly anoxic environment: microbialites would have been refuges in the immediate aftermath of the EPE. Ostracods temporarily disappear together with microbialites during the Griesbachian.