Theme Issue “Renaissance for Paleozoic Eolution Studies: Radiation and Extinction”: Preface for Part 2

This is the Part 2 of the thematic issue; Part 1 was published in Paleontological Research (PR) vol. 25 in 2021. Part 2 adds two more articles that introduce new views and concepts for Paleozoic paleontology, i.e., one for Early-Middle Paleozoic microfossil studies from the long-term terra incognito, central Asia, and the other for essential reconsideration of the causes for the Phanerozoic major extinctions from a non-conventional cosmoclimatology viewpoint. Obut (2023) introduces the latest knowledge on Early Paleozoic micropaleontology from Siberia where precious pieces of information are potentially archived for the lost ocean called the Paleo-Asian Ocean. In addition to classic fossils, such as graptolites and trilobites, a long list of conodonts and radiolarians recently became available from cherts, mudstones, and some limestones. These new fossil data provide prime clues for reconstructing the biogeographic provinciality and geotectonic setting of the Paleo-Asian Ocean. It is noteworthy that the essential research scheme for those ancient mid-oceanic sediments was imported from Japan (e.g. Buslov and Watanabe, 1996; Iwata et al., 1997; Uchio et al., 2004; Ota et al., 2007), and thus is highly suitable for publication in PR. Isozaki (2023) reviews studies on the causes of the Phanerozoic mass extinctions, emphasizing the categorization of previously proposed causes into four distinct groups (see Isozaki, 2019). Besides the currently widely discussed possible causes, such as bolide impact and a large igneous province, a new possibility—non-bolide extraterrestrial effects—is explored on the basis of the astrophysical observations of galaxies (e.g. Rocha-Pinto et al., 2000; Ruiz-Lara et al., 2020) and a new line of material evidence from deep-sea cherts in Japan. The latest finding of an unusually high helium isotope ratio (3He/4He) from the Permo-Triassic boundary extinction interval (Onoue et al., 2019; Takahata et al., 2019) suggests that our Solar System had encountered a dark cloud and that abundant interplanetary dust particles have Theme Issue “Renaissance for Paleozoic evolution studies: radiation and extinction”: Preface for Part 2