Biogeographical distribution patterns in Early Palaeozoic Rostroconchia (Mollusca)
Michael R. W. Amler, Nicole S. Rogalla, 2013. "Biogeographical distribution patterns in Early Palaeozoic Rostroconchia (Mollusca)", Early Palaeozoic Biogeography and Palaeogeography, D. A. T. Harper, T. Servais
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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 of Ribeiria and Eopteria in 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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The Early Palaeozoic was a critical interval in the evolution of marine life on our planet. Through a window of some 120 million years, the Cambrian Explosion, Great Ordovician Biodiversification Event, End Ordovician Extinction and the subsequent Silurian Recovery established a steep trajectory of increasing marine biodiversity that started in the Late Proterozoic and continued into the Devonian. Biogeography is a key property of virtually all organisms; their distributional ranges, mapped out on a mosaic of changing palaeogeography, have played important roles in modulating the diversity and evolution of marine life. This Memoir first introduces the content, some of the concepts involved in describing and interpreting palaeobiogeography, and the changing Early Palaeozoic geography is illustrated through a series of time slices. The subsequent 26 chapters, compiled by some 130 authors from over 20 countries, describe and analyse distributional and in many cases diversity data for all the major biotic groups plotted on current palaeogeographic maps. Nearly a quarter of a century after the publication of the ‘Green Book’ (Geological Society, London, Memoir 12, edited by McKerrow and Scotese), improved stratigraphic and taxonomic data together with more accurate, digitized palaeogeographic maps, have confirmed the central role of palaeobiogeography in understanding the evolution of Early Palaeozoic ecosystems and their biotas.