Freshwater gastropods across the Cretaceous–Paleogene boundary in the Songliao Basin, north-east China

Gastropod faunas from the Cretaceous–Paleogene (K/Pg) boundary transition in the well-dated Songliao Basin (north-east China, East Asia) have been studied. In total, 673 specimens were counted, of which about 80% (n = 538) could be identified. In all, eight species, belonging to six genera, have been identified, including Hydrobia? datangensis, Mesolanistes cf. nanxiongensis, Valvata jiaolaiensis, Valvata shakengensis, Tricula sp. 1, Tricula sp. 2, Zaptychius sp., Planorbidae gen. et sp. indet. and Helisoma dongdawusuensis. Combining data on species ranges in the Jiaolai and Pingyi basins of eastern China, it is shown that three out of 11 species went extinct during K/Pg boundary perturbations. Therefore, we conclude that freshwater gastropods in East Asia underwent minor extinction (c. 18% extinction rates; 72% survival rates). These snail faunas were not affected by short-lived detrimental conditions related to K/Pg boundary perturbations, such as darkness, cooling and starvation, because most of these genera are micro-herbivorous and/or micro-omnivorous grazers (including detritivores) that fed on bacterial films, algae and diatoms or ingested carrion and fine organic deposits. The global mass extinction event at the K/Pg boundary in freshwater environments has rarely been studied, meaning that the present study may help to understand patterns of selective extinction.