The strontium isotopic composition of the oceans changed markedly at the Cambrian-Ordovician transition, some 500 million years ago. This isotopic shift was greatly affected by the first bio-invasion of the land and the ensuing terrestrial-surface environments in a chain reaction that included: 1) an attenuation of weathering on land, 2) changes in the outflow patterns of fluvial floods and the circulation patterns of groundwater, 3) marked regional differentiation of coastal environments, 4) the formation of soil layers, and 5) the eutrophication of estuaries by nutrient salts of terrestrial-biosphere origin. A series of these environmental changes culminated in the marine Ordovician biodiversification, an explosive flourishing of the Paleozoic evolutionary fauna that is characterized by a variety of filter and suspension feeders. The bio-invasion onto land was one of the greatest geobiological events in the Earth's history.

The Great Ordovician Biodiversification Event (GOBE) introduced both dramatic increase in taxonomic diversity and the complexity of community structure in the marine realm. However, relative few works have assessed comprehensively the changes of sedimentary systems in shallow-marine settings responding to the GOBE. Data presented here illustrate that the sedimentary systems on the South China and North China paleoplates changed markedly as a consequence of the first major phase of the Ordovician biodiversification. Pre-GOBE sedimentary systems in the Tremadocian display widespread microbialites and flat-pebble conglomerates and the indigent extent of bioturbation. Through the transitional period of the early Floian, the sedimentary system in the rest of the Early and Mid Ordovician changes to GOBE-type, characterized by intensive bioturbation and vanishing flat-pebble conglomerate and subtidal microbial sediment. The irreversible changes in the sedimentary systems in North and South China may be a consequence of the Ordovician biodiversification instead of its environmental background. Further detailed and quantitative field studies on the changes in sedimentary systems are crucial for understanding the ultimate causes of the GOBE.

Reefs have formed recurrently in the Phanerozoic and occupied a central place in the development of Earth's complex interactions; as such, reefs are essentially a microcosm of the geobiological system. The long-term waxing and waning of reefs was governed not only by the evolution of organisms themselves, but also by cyclical marine conditions (e.g., calcitic sea vs. aragonitic sea; greenhouse vs. icehouse; oligotrophy vs. eutrophy; and carbonate saturation states) that led to the replacement of dominant kinds of taxa. Viewed in perspective, Palaeozoic to Mesozoic reefs changed fundamentally, particularly during greenhouse periods, due to the shifts in marine environmental regimes and ensuing improvements. Metazoan reefs formed temporarily immediately after the earliest Cambrian biomineralization and subsequently became dominant after the Ordovician radiations, as a consequence of networked geobiological interrelationships that were triggered by the invasion of biota onto land. Major extinctions were also triggers for the subsequent (re)diversifications of preexisting, potential reef builders, not necessarily accompanied by new higher taxa, and for the replacement of dominant organisms, whether reef builders or not. Given that certain regimes persisted, progressive, internal modifications and improvements also accelerated in accordance with niche exploitations that are clearly evidenced by changes in the overall growth morphologies of reef builders. Reefs as a microcosm should be further deciphered in light of how both skeletal organisms and microbes mutually responded to ambient, changing habitat conditions, and how sequential contributors prevailed in turn under given conditions at various spatio-temporal scales. Such studies would elucidate the evolution of geobiological constituents and their interrelationships with the underlying background, and more importantly, irreversibly progressive changes in Earth history.

In an attempt to understand the timing and structure of post-Paleozoic adaptive radiation of bivalves, temporal patterns of origination of extant heteroconch families were analyzed, based on the normalized number of originated families per 6 My (NNFO). The mean value through the Mesozoic and Cenozoic is 1.34. The origination occurred temporally unevenly. Three intervals and two events which are characterized by higher rate of origination of families were recognized; Carnian to Hettangian, Mid-Cretaceous, and Paleocene/Eocene Origination Intervals, and Campanian and Lower Miocene Origination Events. Each origination interval or event appears to be characteristic of a salinity regime. Freshwater families originated only in the Late Triassic and Neogene. In contrast, nearly all the families that originated in the Late Cretaceous were marine. This appears to match the Wilson Cycle corresponding to continental aggregation and separation. The actual rather complex pattern of heteroconch family origination recognized in this study is probably a composite of such effects of the long-term pattern associated with the Wilson Cycle, change in nutrient level, predation pressure, and seawater chemistry.

The radiolarian faunal changes across the Permian/Triassic boundary and during Bajocian (early Middle Jurassic) time in Japan are briefly summarized, and the relationships between the radiolarian faunal changes and the paleoenvironmental changes are discussed in this paper. The cause of the radiolarian faunal change from the latest Permian to earliest Triassic time is not well understood, but it is believed due to rapid changes in the marine environment that were disadvantageous to radiolarians. The survival of radiolarians depends on temperature, depth (quantity of light), the amount of dissolved oxygen, nourishment, food and so on. Moreover, it is possible that difference in shell structure may have allowed survivors to adapt more easily to the rapid environmental change across the Permian/Triassic boundary. The Bajocian radiolarian fauna in the Unuma section, central Japan is composed of about 320 species in each horizon and the total reaches about 510 combined in 5 horizons. About 50 originated species were estimated to replace the extinct species per 0.7∼0.8 million years interval. This pattern of radiolarian faunal change through the section is steady and is concordant with the model of steady faunal change. However, the pattern of change is not steady in orders (Spumellaria and Nassellaria) and some families, respectively. It is thought that the section reflects the mixture extent of the cold water mass (the paleo-Oyashio current) and the warm water mass (the paleo-Kuroshio current). Although the outline of faunal change of Paleozoic-Mesozoic radiolarians has been briefly documented, the details of the process in the extinguishing, recovering and stable periods are not clear except for some studies. Combining our knowledge of the early-middle Paleozoic events, the Permian/Triassic boundary event and the Triassic/Jurassic boundary event, it becomes clear that the main extinction events of the Paleozoic-Mesozoic radiolarian faunas happened in greenhouse periods. This means the marine environmental changes that influenced remarkably the radiolarian faunas were caused easily during the greenhouse periods.

A new genus (Triassiphaeodina gen. nov.) and two new species (Medusetta japonica sp. nov. and Triassiphaeodina niyodoensis sp. nov.) of Late Triassic (Rhaetian) phaeodarian Radiolaria are described from a phosphatic nodule found in mélange rocks of the Northern Chichibu Belt, Shikoku, Japan. The Rhaetian age of the nodule and of the phaeodarian new taxa is based on co-occurring Polycystina Radiolaria, including Bipedis acrostylus Bragin, Livarella densiporata Kozur and Mostler, Fontinella primitiva Carter, and Ferresium sp. A of Carter (1993). This finding shows that phaeodarian Radiolaria were already represented in Late Triassic oceans, with morphologies similar to those known in the Late Cretaceous and Cenozoic, from which they have previously been reported. The new taxa described herein represent the oldest known phaeodarian fossils.

This study describes a brachiopod fauna, consisting of 15 species in 15 genera, from the Upper Permian Tsunemori Formation of the Akiyoshi area, southwest Japan. The fauna includes a new species, Cathayspirina magna. The Tsunemori fauna is a Boreal-Tethyan mixed fauna and is closely allied with the Late Permian (Changhsingian) brachiopod faunas of Nabekoshiyama in the South Kitakami Belt, northeast Japan, and of Kawahigashi in the Maizuru Belt, southwest Japan. Palaeobiogeographical data derived from the Tsunemori fauna suggest that the Late Permian accretion site of the Akiyoshi Terrane, including the Tsunemori Formation, was located within a trench along the eastern margin of North China (Sino-Korea).

A refined foraminiferal biostratigraphy of the Middle Permian Kamiyasse Formation in the Kamiyasse area north of Kesennuma, Southern Kitakami Terrane, NE Japan, is presented. Based on the stratigraphic distribution of schwagerinid and neoschwagerinid fusulinoideans, the Kamiyasse Formation, equivalent to the Kanokura Formation in the type area (Setamai-Yahagi area), is subdivided into the Monodiexodina sutchanica, Parafusulina motoyoshiensis and Lepidolina shiraiwensis Zone in ascending order, all of which appear to correspond to the Midian (latest Wordian to Capitanian) in age. The M. sutchanica Zone is here defined as integrated with cross-stratified sandstone beds in the bottom of the formation, and this zone is no longer equivalent to the previously defined M. matsubaishi (junior synonym of M. sutchanica) Zone in the Iwaizaki Limestone and the Kanokura Formation of the type area. The other two zones are defined with the first occurrences of the zonal species. Foraminifers are highly diverse along the stratigraphic interval between the Parafusulina motoyoshiensis and Lepidolina shiraiwensis Zones. Fifty-seven species belonging to 42 genera of foraminifers are identified. Nineteen species among them are systematically described and discussed, including the following three species: Baisalina rikuzenensis sp. nov., whose middle and later whorls are subdivided into more than fifteen chamberlets by septal protrusions; Wutuella sp., previously misidentified as “Cancellina” sp.; and Septagathammina sp., exclusively known from South China.