The impact of the Late Devonian Hangenberg anoxic event on ostracod faunas

International audienceThe Kellwasser event (-372 Myr) is one of the five major extinction events. It is followed by the Hangenberg event (-359 Myr) sometimes considered as equally intense. Both were caused by an accumulation of factors including volcanism and climate change. The Hangenberg event remains little studied and many points need to be clarified, particularly concerning its intensity and the recovery of ecosystems. The aim of this work is to synthesize the impact of the Hangenberg event on marine ostracods. It is based on data from publications, gathering all available information to explore the diversity of ostracods at the Devonian-Carboniferous transition.This event caused the disappearance of about 65% of ostracod species and its impact varies according to their ecology. Thus, it was less intense than the Kellwasser event through which 75% of ostracod species became extinct. However, it could be responsible for the disappearance of the Leperditicopida, large putative ostracods characteristic of Palaeozoic lagoonal environments. Faunal recovery of marine ostracod assemblages was very dependent on environmental variations, particularly those associated with the basal Carboniferous transgression. Two main factors have been involved in post-event recovery: diversification of surviving lineages; and recolonization of neritic environments by speciation of deeper water faunas having survived in refuge areas