Early-Middle Ordovician cephalopods from Ny Friesland, Spitsbergen – a pelagic fauna with Laurentian affinities

The collection of cephalopods from eight sampling horizons within the Olenidsletta Member, Valhallfonna Formation, Floian–Dapingian, Profilstranda and nearby Profilbekken, Ny Friesland, Spitsbergen, resulted in detection 31 species, 20 genera, 12 families Ellesmerocerida, Endocerida, Riocerida, Dissidocerida, Orthocerida, Tarphycerida, Oncocerida. Of these, five genera (Ethanoceras gen. nov., Hinlopoceras Nyfrieslandoceras Olenidslettoceras Svalbardoceras nov.) 19 species (Bactroceras fluvii sp. Buttsoceras buldrebreenense Cycloplectoceras hinlopense Cyclostomiceras profilstrandense Deltoceras beluga Eosomichelinoceras borealis Ethanoceras solitudines et Hemichoanella occulta tempestatis H. venti Lawrenceoceras ebenus L. larus Litoceras profilbekkenense bassleroceroides farmi Protocycloceras minor Proterocameroceras valhallfonnense sterna S. skua are new. diagnoses Cyptendoceratidae, Bactroceratidae Hyatt, 1894 emended. Well preserved early growth stages several remarkable. Turnover between intervals is high. differences composition, diversity evenness assemblages interpreted as reflecting changing depth oxygenation depositional bottom conditions. co-occurrence endemic cosmopolitan resulting a high vertical niche differentiation eustatically generated lateral shifts facies zones. Based on calculations phragmocone implosion depths, depths 50–130 m plausible for supporting independent evidence biomarker signatures. Several cephalopod Member represent odd mosaics morphological features previously known which cannot be unambiguously assigned to one existing higher taxa. Results cladistic analysis shed new light evolution Oncocerida Orthocerida.