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 The purpose of this volume is to list all systematically treated or illustrated Paleozoic Crinoidea for the years 1986 through 1990. Initially it was planned to include the Coronate Echinoderms; however none were illustrated or systematically treated during the 1986 through 1990 interval. This volume continues and updates GSA Memoir 137, Bibliography and Index of Paleozoic Crinoids 1942-1968 (Webster, 1973); GSA Microform Publication 8, Bibliography and Index of Paleozoic Crinoids 1969-1973 (Webster, 1977); GSA Microform Publication 16, Bibliography and Index of Paleozoic Crinoids 1974-1980 (Webster, 1986); and GSA Microform Publication 18, Bibliography and Index of Paleozoic Crinioids and Coronate Echinoderms 1981-1985 (Webster. 1988).

Abstract The purpose of this volume is to list all systematically treated or illustrated Paleozoic Crinoidea for the years 1986 through 1990. Initially it was planned to include the Coronate Echinoderms; however none were illustrated or systematically treated during the 1986 through 1990 interval. Although I do not agree with the identification of many of the species or genera as indexed, I am not attempting to reassign them. I leave that up to later workers who are systematically treating the species involved. I hope that this compilation facilitates their work as it does my own.

Disarticulated Permian crinoid columnals and pluricolumnals, up to 9 cm in diameter, from exotic carbonate blocks in the base of the Zamora Formation, found along Arroyo Zamora near El Volcan, Baja California, Norte, are among the largest ever reported. The relatively inflexible columns that these columnals and pluricolumnals formed are interpreted to have lived in relatively strong currents along the edge of the shelf or upper slope. They are designated Apletoanteris bajaensis n. gen. and n. sp.

Sedimentary interbeds preserved between flows of the Columbia River Basalt Group provide a record of the depositional and erosional conditions that characterized the Columbia Plateau between eruptions of basalt. Examination of the sedimentary, stratigraphic, and petrologic character of the Sweetwater Creek interbed from within the Lewiston basin of southeastern Washington and north-central Idaho allows insight into the paleogeographic conditions that existed following eruption of the Priest Rapids Member of the Wanapum Basalt, ca. 14.5 Ma. The Sweetwater Creek interbed is composed of generally unconsolidated and inter-stratified beds of clay, silt, sand (with local thin gravel stringers), and volcanic ash-rich sediment. Three broadly defined sedimentary facies are identified on the basis of lithology and texture. The spatial distribution of these facies, abundance of clay- and silt-rich sediment, and internal sedimentary structures suggest that deposition of the interbed resulted primarily from fluvial and mixed fluvial-lacustrine sedimentation. Fluvial drainages that headed in the ancestral Clearwater Mountains entered the Lewiston basin on the east and exited to the northwest. Basin streams appear to have been primarily of the meandering, mixed-load type. Channel sands deposited by these streams were concentrated east and north of the basin center, and transported extrabasinal sediments are characterized by plutonic and metamorphic sand- and gravel-sized clasts. Fine-grained silt- and clay-rich flood-plain and associated lacustrine deposits extend across the basin, but are thickest near the basin center. The Umatilla basalt flow entered the Lewiston basin during deposition of the Sweetwater Creek interbed and locally invaded fine-grained lacustrine sediments. A later flow, the Wilbur Creek basalt, partially buried the interbed. Complete burial of the Sweetwater Creek interbed sediments followed eruption of the Asotin flow.