Palaeobiography and Biodiversity Change: the Ordovician and Mesozoic-Cenozoic Radiations

Abstract

J. Alistair Crame and Alan W. Owen, 2002, Geological Society of London Special Publication 194, Geological Society, London, 206 p. (Hardcover, US $108.00) ISBN: 1-86239-106-8. This book resulted from the 2001 Lyell Meeting where Alistair Crame and Alan Owen brought together two groups of paleontologists whose interests are so widely separated in geologic time that they would seldom rub elbows. As study of the great radiations of life begins to compete with the extinction debates as a major focus, paleontology will lose some of the attention it has received because of the appeal of catastrophes to the general public. However, the future will be no less contentious within the paleontological community. Even sorting out what radiations are and how they proceeded will take some time. This book takes a look at two radiations—a straightforward task at first sight, but the radiations are so different that comparisons are no easy matter. The Ordovician Radiation was abrupt, taking place, for the most part, in the Arenig, with a sudden pulse in the Late Arenig at about the base of the Laurentian Whiterock. In terms of biogeography the primary phase of the Ordovician radiation took place in such a short interval that the continental positions were essentially stable. The Mesozoic–Cenozoic radiation took place during such a long interval that plate motions provided a means of distribution and interrupted pathways of dissemination. Entire climatic regimes changed. Even the initiation of the radiations differed. As yet no unusual biotic event has been recognized preceding the Ordovician radiation (although one is suggested here) while the largest mass extinction in earth history set the stage for the Mesozoic radiation. Most contributions are detailed examinations of specific biotic changes that took place during one or the other of the radiations, with little space devoted to comparisons of groups …