The geographical distribution of rostroconch taxa of the orders Ribeirioida and Conocardiida, mostly across the equatorial continents and oceans, is compiled for six presumed diversity acmes in the early Early Ordovician (c.485 Ma), the late Early–early Middle Ordovician (c.475 Ma), the Late Ordovician (c.455 Ma), the Early Silurian (c.435 Ma), the late Early–early Late Silurian (c.425 Ma) and the early Early Devonian (c.415 Ma), based on our present, uneven knowledge. Rostroconchs show distribution patterns which enable a provisional separation of biogeographical provinces at least from the Silurian onward, comparable with Late Palaeozoic rostroconch distributional patterns. The distributions of tabulate corals, trilobites and bivalves appear roughly comparable, but not the nektic and planktic groups. A restriction to low latitudes (‘tropical’ realms) is clear for members ofRibeiriaandEopteriain the Early Ordovician, similar to proven patterns for hippocardiid rostroconchs from the Late Silurian onward until the Middle Permian. Preliminary rostroconch provinces or subprovinces, respectively, are currently discernable in the Silurian and Devonian for northwestern Laurentia, south-central Laurentia/Baltica and the north-central margin of Gondwana (i.e. Perunica, Bohemia). Rostroconch distributional data for SE Asia, China, Kazakhstan, Siberia and Australia are sparse and require further studies.

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ABSTRACT. The gastropod fauna of the Upper Devonian Baggy and Pilton formations in south-west England is revised and includes some 30 taxa. The topmost part of the Upper Famennian succession in Devon is represented by clastic near-shore and shallow shelf sediments, indicating a short-term transgressive phase (`Strunian Transgression'). The sequence yields a highly diverse fauna dominated by brachiopods and ostracodes, locally supplemented by crinoids, bryozoans, trilobites and molluscs. The taxa`Patellostium' britannicum sp. nov., Angyomphalus (Angyomphalus) junius sp. nov. and Dictyotomaria eurocapillaria sp. nov. are erected; a junior homonym is replaced by Macrochilina? piltonensis nom. nov. The gastropod fauna displays an independent character, where latest Devonian faunal elements overlap with Late Palaeozoic taxa expressing a transition similar to that of the bivalves, brachiopods, echinoderms and corals, without a sharp faunal break at the Devonian/Carboniferous boundary. Apart from the Caenogastropoda, all subclasses of gastropods are represented. Members of the bellerophontoids, pleurotomarioids and loxonematoids are most abundant, followed by murchisonioids, naticimorphs, euomphalomorphs and platyceratoids. The various gastropod groups represent different ecological demands and trophic categories, and together with the accompanying fauna indicate that nearly all habitats and niches were occupied in the shallow South Laurussian Shelf. A M O N G fossil associations from the middle and upper Palaeozoic, latest Devonian (Late Famennian) faunas worldwide have not attracted special attention as they are mainly scarce, badly preserved and not well understood, although most of them have been known for over 100 years. Only those localities important for establishing the Devonian/Carboniferous boundary have been intensively sampled and studied in detail.Some ten years ago, an interdisciplinary research project was initiated by one of us (MRWA) dealing with the study of biofacies evolution and palaeobiodiversity in siliciclastic shelf regions before and after evolutionary turning-points. The selected study area was the southern margin of Laurussia during the Devonian and early Carboniferous because sedimentary rocks of that age and facies are widely distributed geographically and palaeogeographically from eastern North America across the British Isles and Belgium as far as the Russian Platform. The idea for this study arose from the inadequate knowledge about the palaeontology of siliciclastic and mixed siliciclastic-carbonate shelf areas, although they display good preservation potential.The multidisciplinary studies of invertebrate faunas are now leading to a more detailed picture of the bio-and lithofacies evolution, palaeoecology, biogeography, palaeoclimatology and small-scale palaeogeography of the South Laurussian Shelf. Within the scope of the project we selected several topics for analysis, one of which being the study of the fauna, stratigraphy and biofacies of the Pilton-Condroz Shelf (from south-west ...

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