A review of the Early Palaeozoic biogeography of bryozoans
Caroline J. Buttler, Patrick N. Wyse Jackson, Andrej Ernst, Frank K. Mckinney, 2013. "A review of the Early Palaeozoic biogeography of bryozoans", Early Palaeozoic Biogeography and Palaeogeography, D. A. T. Harper, T. Servais
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The palaeogeographical distributions of Early Palaeozoic bryozoan faunas are reviewed. Previous studies are examined and new databases have been assembled of the stratigraphical and geographical distribution of Ordovician and Silurian taxa. Analysis was carried out using cluster analysis based on Jaccard’s coefficient and paired group method, as well as principal coordinate analysis based on Jaccard’s coefficient, to examine the relationships between different localities. Bryozoan faunas increased in diversity throughout the Ordovician peaking with 133 genera during the Katian. In the earliest Ordovician provincialism is difficult to determine, but by the Darriwilian five distinct provinces developed, decreasing to four in the Sandbian. There was a decrease in provinciality throughout the Katian as faunas became less endemic, caused by the reduction of geographical barriers. Following the extinction of many genera at the end of the Ordovician, early Silurian faunas contain remnant taxa. Subsequently fenestrates began to dominate faunas. During the Llandovery bryozoans began to show distinct provincialism, but this declined during the Wenlock, only to re-emerge during the Ludlow. Late Silurian (Pridoli) faunas are sparse but nevertheless show possible division into two provinces.
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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.