Heterogeneous palaeo‐ecogeography of brachiopods during the Late Ordovician mass extinction in South China

Abstract Following the first phase of the Late Ordovician mass extinction (LOME), the globally distributed Hirnantia brachiopod fauna exhibited homogeneity both latitudinally and longitudinally. The uniform global palaeobiogeography of the Hirnantia fauna, based solely on occurrence data, might obscure its heterogeneous nature during the glaciation. In this study, leveraging diversity and abundance data from well‐sampled collections in South China, along with non‐metric multidimensional scaling (NMDS) using the Raup–Crick measure, network analysis (NA), and abundance models, we unveil the palaeo‐ecogeography of the Hirnantia fauna for the first time. The distribution of the Hirnantia fauna in South China is categorized into three areas: the deep water area, the shallower water area, and the very shallow water area, based on NMDS and NA. Drastically different benthic assemblages among these areas reveal diverse environmental settings, with an approximate westward shallower trend and a deeper trend extending both northward and southeastward. Analysis of species‐abundance models for eight well‐sampled collections demonstrates different best‐fitted models, suggesting that competitive ecology operated in varied contexts despite common BA3 environmental settings and close geographical proximity. While a substantial global sea level fall and climate cooling around the Katian–Hirnantian boundary played important roles in the LOME, the palaeo‐ecogeography of the Hirnantia fauna in South China was predominantly influenced by the expansion of the Cathaysian oldland and the Qianzhong uplift. The interval between the two LOME phases, marked by kinetic conditions, witnessed the heterogeneous development of the Hirnantia fauna.