This special issue deals with Extreme environments and biotic responses during the Neoproterozoic-Phanerozoic transition and comprises 23 papers. In this preface, we summarise the major findings and place them in a wider context. Some key discoveries are as follows: (1) After the Marinoan global glaciation (end-Cryogenian), a rise in seawater carbon isotopic composition of dissolved inorganic carbon (δ¹³C_DIC), together with various biomarkers, indicate an increase in marine primary productivity, and imply a postglacial increase in atmospheric O₂ level by 3.813.4% of present atmospheric levels. (2) The earliest Cambrian sulfidic ocean was characterized by widespread but low levels of microbial sulfate reduction (MSR) in seawater with active microbial iron reduction in sediment porewaters; this state differs from present day sulfidic water masses, such as those in the Black Sea, which show predominantly MSR in the sediment. Multiple geochemical proxies demonstrate that a dynamic ‘euxinic wedge’ may have existed at mid-water depths, and its expansion/contraction controlled redox variations during the early Cambrian. (3) Studies of Hg concentration and isotope analyses shed new light on the Late Ordovician mass extinction event, and reveal that volatile volcanism probably acted as a trigger for several catastrophes, involving climate change, ocean acidification, and anoxia. (4) Other findings show that primitive foraminiferans may have occurred already prior to the Cambrian Explosion, brachiopod-dominated shell beds were already present in the early Cambrian, and reef-builders diversified during the Middle Ordovician, altering our understanding of Cambrian-Ordovician evolution. The papers in this special issue therefore improve knowledge of the Neoproterozoic-Phanerozoic transition and will be of interest to a broad readership of palaeontologists and earth system scientists.

本期特刊涉及新元古代-显生宙过渡期间的极端环境和生物反应，共包含 23 篇论文。在本序言中，我们总结了主要发现并将其置于更广泛的背景中。一些主要发现如下： (1) 在马里诺全球冰川期（低温纪末）之后，溶解无机碳（δ ¹³ C _DIC）的海水碳同位素组成上升，连同各种生物标志物，表明海洋原生生产力，并意味着冰期后大气中的 O ₂水平增加了 3.8目前大气水平的 13.4%。(2) 最早的寒武纪硫化海的特点是海水中微生物硫酸盐还原（MSR）广泛但水平低，沉积物孔隙水中微生物铁还原活跃；这种状态不同于当今的硫化水团，例如黑海中的那些，后者在沉积物中主要表现出 MSR。多个地球化学代理表明，在中水深度可能存在一个动态的“euxinic楔”，并且它的膨胀/收缩控制了早寒武世期间的氧化还原变化。(3) 汞浓度研究和同位素分析为晚奥陶世大灭绝事件提供了新的线索，并揭示了挥发性火山活动可能引发了包括气候变化、海洋酸化和缺氧在内的几场灾难。(4) 其他研究表明，原始有孔虫可能在寒武纪大爆发之前就已经出现，早寒武世已经存在以腕足类动物为主的壳层，中奥陶世造礁者多样化，改变了我们对寒武纪-奥陶纪演化的认识. 因此，本期特刊中的论文提高了对新元古代-显生宙过渡的认识，并将引起古生物学家和地球系统科学家的广大读者的兴趣。