The Aras Valley section (NW Iran) exposes a sedimentary succession that allows to study ostracod diversity patterns during/across the end-Permian mass extinction because of its ubiquitous fossil record. For the present study, 59 samples were investigated for their ostracod abundances, which ranged from 4 to 31500 specimens per 500 g. In 45 sample horizons, the ostracods were identified to the species-level. In total, 3,425 specimens were determined and 62 species were identified, of which one genus and ten species are described for the first time: Fabalicypris veronicae Gliwa, sp. nov., Orthobairdia capuliformis Gliwa, sp. nov., Araxobairdia formosa Gliwa, gen. et sp. nov., Bairdiacypris kathleenae Gliwa, sp. nov., Eumiraculum mettei Gliwa, sp. nov., Liuzhinia julfensis Gliwa, sp. nov., Carinaknightina hofmanni Gliwa, sp. nov., Cavellina fosteri Gliwa, sp. nov., Cavellina hairapetiani Gliwa, sp. nov. and Hungaroleberis striatus Forel, sp. nov. The assemblages show, at the end-Permian mass extinction event, a complete turnover from a low-diversity Fabalicypris-dominated pre-extinction community to a more diverse Bairdiacypris-dominated post-extinction community. The turnover coincides with the significant temperature increase that was previously recorded from NW Iranian sections. The low diversity in the horizon immediately below the extinction horizon indicates that environmental changes, such as thermal stress, may have had an impact on the ostracod assemblages prior to the extinction event. In comparison with other diverse ostracod assemblages from the Palaeotethyan realm, the ostracods of the Aras Valley section are not associated with microbialites.

Occurrences of ostracod specimens per species and sample horizon.