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 Anomalocystitid mitrates represent one of the most diverse and long ranging clade of stylophorans (Early Ordovician–Middle Devonian). Although they probably originated from a peri-Gondwanan stock of early mitrocystitids during the Floian, the fossil record of anomalocystitids in the Middle–Upper Ordovician of the Mediterranean Province remains extremely scarce and largely underestimated. The unusually shaped anomalocystitid genus Diamphidiocystis was originally described in the latest Katian–Hirnantian of North America (Illinois). However, earlier occurrences of this genus in the late Darriwilian of western France (Brittany) suggest a probable peri-Gondwanan origin. Based on new Middle to Late Ordovician material from the Anti-Atlas (Morocco), Bohemia (Czech Republic) and Brittany (France), all occurrences of Mediterranean Diamphidiocystis are considered as conspecific and formally described as D. regnaulti sp. nov. The palaeobiogeographical significance of Ordovician anomalocystitid mitrates is discussed.

ABSTRACT From 1840 to 1845, Roderick Murchison (1792–1871), an accomplished geologist who was instrumental in developing the Paleozoic portion of the geologic time scale, traveled in Europe, Scandinavia, and Russia, where he documented the occurrence and extent of the Silurian, Devonian, and Permian Systems. A key component of his fieldwork methodology was to examine fossils in both private collections and public museums to assess the types of fossils that occur in a region, in order to guide and expedite his mapping efforts. While working in Scandinavia, he examined fossil collections in Copenhagen, Oslo, Stockholm, Upsala, and Visby, and those collections clearly influenced his choice of travel routes and, ultimately, the geologic map (plate VI) in The Geology of Russia (Murchison et al., 1845). Furthermore, he was able to compare the Scandinavian fossils to British collections, thereby confirming the age of the strata he was mapping. The results of Murchison’s work appeared in numerous papers as well as two major books, The Geology of Russia (Murchison et al., 1845) and Siluria (Murchison, 1854), thereby advancing knowledge of Scandinavian stratigraphy. Not only were the fossil collections in the museums of his day essential to Murchison’s scientific research, but collections of documents in modern archives are invaluable in reconstructing his movements, observations, and discoveries more than 170 years ago, thereby demonstrating the utility of collections and museums to the construction of knowledge.