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, Memoir12, 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.

The various chapters of this book have been written by researchers who are still working in the Canadian Inland Seas region. The chapters synthesize what is known about these seas, yet much still is to be learnt. It is hoped that this collection of information will serve as a springboard for future, much needed, studies in this fascinating, diverse region, and will stimulate comparative analyses with other subarctic and arctic basins of the world. The Canadian Inland Seas are the only remnants, albeit cold, of the ancient cratonic marine basins which occupied central North America throughout the Paleozoic and part of the Mesozoic. Precambrian rocks and gently dipping Paleozoic sedimentary rocks underlie the seas. The area is also close to the centers of Pleistocene glaciations. The coastal areas represent an emerged landscape of the post-glacial Tyrrell sea, as the region has been isostatically uplifted to about 350 meters since glacial times. A total of 56 fish species inhabit Hudson Bay and James Bay. Seals, whales and one of the largest and southernmost populations of polar bears inhabit the seas as well. The coastal areas are important habitats for migratory bird populations, some of which migrate from as far away as Southern Argentina. The ostic environment has preserved these regions relatively unchanged by man, with only a major harbour at Churchill, Manitoba, which is active for part of the year, and a second large, rail-terminal settlement in the south at Moosonee, Ontario. A few, small, native Indian and Inuit villages dot the coasts. The seas are being affected indirectly by the damming of rivers for the generation of hydroelectric power, and by drainage diversions towards the man-made reservoirs. A major project is being completed in Quebec east of James Bay, but other rivers in Ontario and Manitoba have been dammed as well. Undoubtedly freshwater is one of the more important resources of the area, however its exploitation needs careful thought because of the possible long-range effects on the environment, particularly the coastal marshes, which sustain much of the eastern American intercontinental migratory avifauna. Other resources occur in the regions, primarily minerals and perhaps petroleum. For the most part however, such resources remain to be discovered.