Early Silurian brachiopods (Rhynchonellata) from the Sælabonn Formation of the Ringerike district, Norway

A revision of Kiaer's index fossils of "Etage" 6 in the Ringerike district of Norway reveals the pres-ence of four species: Rostricellula wadti sp. nov., Platytrochalos ringerikensis sp. nov., Platytrochalos rabbei sp. nov., and Zygospiraella duboisi. Rostricellula is a common Ordovician rhynchonellide brachiopod and is known to occur in the Lower Silurian as a holdover taxon in only a few localities worldwide. Previously, Platytrochalos was known only from the Lower Silurian (Llandoverian) rocks of Anticosti Island, eastern Canada. The occurrence of this rare genus in the Ringerike district pro-vides additional information for the early evolution and palaeogeography of the taxonomically en-igmatic family Leptocoeliidae. Zygospiraella is regarded as an index genus for the Rhuddanian, and the presence of Z. duboisi provides a useful biostratigraphic control on the age of the Saelabonn Formation.