Diverse earliest Triassic ostracod fauna of the non-microbialite-bearing shallow marine carbonates of the Yangou section, South China

Since diverse ostracod faunas in the immediate aftermath of the latest Permian mass extinction are mainly found within Permian–Triassic boundary microbialites (PTBMs), the idea of an ostracod ‘microbial-related refuge’ has been proposed. Here, we report a diversified earliest Triassic ostracod fauna from the Yangou section in South China, where no PTBMs were deposited, providing evidence inconsistent with this ‘microbial-related refuge’ hypothesis. In addition, a significant ostracod extinction is recorded, corresponding with the earliest Triassic mass extinction (ETME). This ETME of ostracods is associated with size increases and a length/height ratio (L/H) decrease, indicating varied evolutionary patterns of shape and size of ostracods through the Permian–Triassic (P-Tr) extinction events. Although the nature of these biotic changes is somewhat unclear, the temporally varied ‘refuge zone’ scenario provides us with a window to reconstruct the environmental dynamics of ecosystem changes during the P-Tr transition.