Survival and recovery atrypid fauna following the terminal Ordovician extinction, the Atrypinae: central Oslo Region, Norway

The atrypid fauna immediately following the end-Ordovician extinction event is poorly known. Siliciclastic strata of the Solvik Formation in the central Oslo region was deposited during the latest Hirnantian into the Aeronian and contains an uncommonly rich atrypid fauna. The brachiopod subfamily Atrypinae includes three new genera; Askerina, Nottina and Sifella, and six new species; Askerina cymbula, Dihelictera askeriensis, Joviatrypa nakremi, Nottina phalerata, Sifella patera and Zygospiraella nupera. Schachriomonia spiraensis sp. nov. (subfamily Spirigerininae) shows transitional traits to the subfamily Atrypinae. Free-lying, relatively large-shelled genera with many-whorled spiralia and frills like Atrypa developed earlier than previously known with the new genus Askerina occurring in the Ordovician/Silurian boundary layers. A possible gradual evolutionary lineage from Zygospiraella duboisi to Z. nupera sp. nov. is explored. Well-developed fossil assemblages are present from the base of the Solvik Formation. The Formation was deposited at varying depths with deeper shale facies inhabited by Atrypinae like Askerina, Schachriomonia and Protatrypa, shallower calcareous facies showcase Nottina and Dihelictera, whereas the storm-dominated, Aeronian parts of the formation include species of Joviatrypa, Sifella, Zygospiraella and Gotatrypa? Baltica situated in southern tropical to subtropical latitudes had migration of taxa from east to west following the tropical storm track