The commoner brachiopods of the latest Ordovician of the Oslo-Asker district, Norway

The brachiopod fauna of the upper part of the rocks of Ashgill age in the Oslo-Asker area, Norway, is reviewed prior to an assessment of the ecology of the macrofauna found in this Rawtheyan and Hirnantian regressive sequence, a regression caused by the contemporary glacio-eustatic lowering of sea level. Most of the elements of the cosmopolitan Hirnantia Fauna occur, some very commonly, such as Dalmanella, Hirnantia, Eostropheodonta, Cliftonia, and Hindella, but other elements are rare or absent; many additional genera are also noted. In sediments filling tidal channels at the top of the sequence, genera such as Thebesia, Brevilamnulella, and Leptoskelidion are recorded for the first time outside the North American craton. The commoner constituents of the fauna are described and illustrated, and the new species Trematis norvegica, Onniella kalvoya, Leptoskelidion loci, Eoplectodonta oscitanda, and Thebesia scopulosa are erected. The pentameride Holorhynchus is revised and reinterpreted as an ancestral stricklandiid.