Special Issue “Renaissance for Paleozoic Evolution Studies: Radiation and Extinction”: Preface

Familiar landscapes with diverse biota first appeared on our planet through rapid biodiversification immediately after the termination of the Precambrian world, about 540 Myr ago. Since then the first 300 Myr of the Phanerozoic, i.e., the Paleozoic Era, witnessed irreversible changes in global environment in association with the expansion and diversification of eco-spaces, both on land and in the oceans. The causes and processes of this unidirectional evolutionary history during the Paleozoic have often been attributed to multiple punctuated episodes, each of which triggered global-scale environmental changes to constrain the direction of evolution. For example, the Cambrian explosion, the Great Ordovician Biodiversification Event (GOBE), and three major mass extinctions, at the end of the Ordovician, Devonian, and Permian, respectively, are attractive clichés/concepts for these unusual changes that have become extremely popular, not only among professional scientists, but also with journalists. Such elevated interest in Earth history was ignited by some iconic contributions; i.e., the Cambrian Explosion (Gould, 1989), the bolide impact story for the end-Cretaceous timing (Alvarez et al., 1980), the visualization of long-term biodiversity patterns in a clear diagram (Raup and Sepkoski, 1982), and the snowball Earth hypothesis (Kirschvink, 1992; Hoffman and Schrag, 1998). The search for possible causes/drivers of these “big events” of the Paleozoic has continued, yielding numerous scientific articles. In addition to extraterrestrial impact, several stimulating ideas such as ocean redox change and intermittent supervolcanism were proposed as possible key mechanisms during the 1990s; nonetheless, interest started to decline in this century. What remains at present is a huge pile of similar data produced by the same analytical techniques, particularly with various geochemical/isotopic proxies, and many similar discussions from almost the same viewpoints. This may reflect the current overemphasis on quantitative measures for evaluating research, such as the number of citations and journal impact factors, in the scientific community (Garfield, Special Issue “Renaissance for Paleozoic evolution studies: radiation and extinction”: Preface