Cosmopolitanism represents the formation of globally homogenous biotas, usually of low-diversity, and normally form under unusual environmental conditions. But the factors driving such important biogeographic states remain unclear. The Carboniferous to Triassic encompasses the Late Paleozoic Ice Age (LPIA) and a hothouse beginning in the latest Permian and persisting through the Early Triassic. These dramatic environmental changes caused complex paleobiogeographic changes and were also associated with such severe biological events as the mid-Carboniferous biotic crisis, and the end-Permian and end-Triassic mass extinctions. This interval is a unique natural window for studying biogeographic patterns under different climate backgrounds and with greatly changed taxonomic composition. In this study, we apply multiple biogeographic indices to examine two episodes of cosmopolitanism based on global marine invertebrate fossil records during the Carboniferous to Triassic. The LPIA cosmopolitanism event was characterized by high faunal similarity at middle latitudes generated by diversity loss and complex glacial/interglacial climatic changes. By contrast, the EPME cosmopolitanism event was characterized by high faunal similarity globally resulting from a faunal changeover, when communities characterized by high richness were replaced by widespread and monotonous communities with high evenness and extremely low richness. The two cosmopolitanism events differed in durations, taxon preference and geographic influence, but in both cases their driving mechanisms were linked to extreme icehouse and hothouse climates. These two episodes illustrate the complexity of deep time marine ecosystem response to climatic changes and the multiple drivers of cosmopolitanism in the marine biosphere.

世界主义代表了全球同质生物群的形成，通常是低多样性的，并且通常在不寻常的环境条件下形成。但推动如此重要的生物地理状态的因素仍不清楚。石炭纪至三叠纪包括晚古生代冰河时代（LPIA）和始于晚二叠纪并持续到早三叠世的温室。这些剧烈的环境变化引起了复杂的古生物地理变化，并与石炭纪中期生物危机、二叠纪末和三叠纪末大规模灭绝等严重的生物事件有关。这个区间是研究不同气候背景下生物地理格局和分类组成发生很大变化的独特自然窗口。在这项研究中，我们根据石炭纪至三叠纪的全球海洋无脊椎动物化石记录，应用多个生物地理学指数来检查两次世界主义事件。LPIA 世界性事件的特点是由于多样性丧失和复杂的冰期/间冰期气候变化导致中纬度地区的动物群高度相似。相比之下，EPME 世界主义事件的特点是由于动物群转换导致的全球动物群高度相似性，当以高丰富度为特征的群落被具有高均匀度和极低丰富度的广泛而单调的群落所取代时。这两个世界主义事件的持续时间、分类偏好和地理影响不同，但在这两种情况下，它们的驱动机制都与极端的冰室和温室气候有关。