Lituitid cephalopods from the Middle Ordovician of Bohemia and their paleobiogeographic affinities

Cephalopods of the order Lituitida Starobogatov, 1983 are a common component of low-latitude, warm-water fossil assemblages of the Middle and Upper Ordovician strata of Baltica and the Chinese paleocontinents (North and South China, Tarim, Tibet). The lituitids are also known from Laurentia, Siberia and mid-latitude Avalonia and Argentine Precordillera. By contrast, in the high-latitude regions of peri-Gondwana, the group is known only from a ?Trilacinoceras Sweet, 1958 from the late Darriwilian rocks of the Iberian peninsula and Rhynchorthoceras cf. angelini (Boll, 1857) from the upper part of the Klabava Formation (uppermost Dapingian Stage) of Bohemia. The single specimen of the latter species is the earliest known lituitid known from European and African peri-Gondwanan basins. The timing of its appearance coincides with a time interval of an increased faunal interchange between Perunica and Baltica during the late Dapingian time. Six specimens of two lituitids, Lituites lituus de Montfort, 1808 and Trilacinoceras cf. discors (Holm, 1891), are for the first time reported from the late Darriwilian Dobrotivá Formation. Finds of these lituitids are coeval with an occasional dispersion event of another typically low-latitude cephalopod group, the Tarphyceratida, to high latitudes.