Six new and one earlier known thelodont from the Ordovician and Lower Silurian of Severnaya Zemlya Archipelago are described. Scales of the earliest dated thelodont Stroinolepis maenniki n. gen., n. sp. were obtained from the Strojnaya River section, October Revolution Island, upper Ozernaya and Strojnaya formations, Middle-Upper and Upper Ordovician, correspondingly. Loganellia matura n. sp. was found from the Srednii Island, Golomyannyj Formation, middle Llandovery. Paralogania klubovi n. sp. and Loganelliidae gen. et sp. indet. come from the middle(?) Llandovery of Pioneer Island. L. grossi Fredholm, 1990 in the Matusevich River section, Paralogania consimilis n. sp. and Thelodus calvus n. sp. in the Ushakov River section, and Shielia multispinata n. sp., in the Spokojnaya River section, are distributed in the Samojlovich Formation, Wenlock, Lower Silurian of October Revolution Island.
Agnatha, Thelodonti, Middle-Upper Ordovician, Upper Ordovician, Lower Silurian, Severnaya Zemlya Archipelago, Russia, scale morphology, histology