Abstract The palaeobiogeographical distribution of the six major clades of Ordovician echinoderms (asterozoans, blastozoans, crinoids, echinozoans, edrioasteroids and stylophorans) is analysed based on a comprehensive and up-to-date database compiling 3701 occurrences (1938 species recorded from 331 localities) of both complete specimens and isolated ossicles. Although historically biased towards a limited number of regions (Europe, North America, Russia), the resulting dataset makes it possible to identify six main palaeobiogeographical provinces for Ordovician echinoderms: Laurentia, Baltica, West Gondwana, East Gondwana, Avalonia and Siberia. At a global scale, the high endemicity of echinoderms during the Early to Middle Ordovician coincides with the time of maximum dispersal of continental masses. Late Ordovician faunas tend to become more cosmopolitan, possibly as a consequence of changing palaeogeography and/or relatively higher sea-levels in the Sandbian–Katian interval. Regional biodiversity patterns of Ordovician echinoderms confirm that their major diversification during the Ordovician is not a single, universal evolutionary event, but rather results from the complex addition of contrasted local evolutionary trends.

Abstract During the Cretaceous (145.5-65.5 Ma; Gradstein et al. 2004 ). Central Europe was part of the European continental plate, which was bordered by the North Atlantic ocean and the Arctic Sea to the NW and north, the Bay of Biscay to the SW, the northern branch of the Tethys Ocean to the south, and by the East European Platform to the east ( Fig. 15.1 ). The evolution of sedimentary basins was influenced by the interplay of two main global processes: plate tectonics and eustatic sea-level change. Plate tectonic reconfigurations resulted in the widening of the Central Atlantic, and the opening of the Bay of Biscay. The South Atlantic opening caused a counter-clockwise rotation of Africa, which was coeval with the closure of the Tethys Ocean. Both motions terminated the Permian-Early Cretaceous North Sea rifting and placed Europe in a transtensional stress field. The long-term eustatic sea-level rise resulted in the highest sea level during Phanerozoic times ( haq et al. 1988;Hardenbol et al. 1998 ). Large epicontinental shelf areas were flooded as a consequence of elevated spreading rates of mid-ocean ridges and intra-oceanic plateau volcanism, causing the development of extended epicontinental shelf seas and shelf-sea basins ( Hays & pitman 1973 ; Larson 1991 ). A new and unique lithofacies type, the pelagic chalk, was deposited in distal parts of the individual basins. Chalk deposition commenced during middle Cenomanian-early Turanian times. Chalk consists almost exclusively of the remains of planktonic coccolithophorid algae and other pelagic organisms, and its great thickness reflects a high rate of production of the algal tests. The bulk of the grains are composed of lowmagnesium calcite, representing coccolith debris with a subordinate amount of foraminifers, calcispheres, small invertebrates and shell fragments of larger invertebrates ( Håkansson et al. 1974 ; Surlyk & Birkelund 1977 ; Nygaard et al. 1983 ; Hancock 1975 , 1993 ).