First record of a deep-water brachiopod fauna in the Telychian of South China and its paleoecological implications

While the late Llandovery brachiopod faunas of South China are well documented, they are known almost exclusively from shallow-water settings. Here, we present a detailed study of a brachiopod fauna from the Ningqiang Formation (early to middle Telychian) at the Bifengguan section in Sichuan Province, South China. Quantitative analyses, including non-metric multidimensional scaling (NMDS) and network analysis, reveal three successive brachiopod associations. Significantly, the basal Aegiria – Epitomyonia association was characterized by the abundance of the deep-water indicator Epitomyonia. This represents the first definitive record of a deep-water (BA4) community within the Telychian Xiushan Fauna, which was previously thought to be restricted to shallower environments. This basal association is succeeded by the Aegiria – Megaspinochonetes and Fardenia – Striispirifer associations, and this complete succession indicates a shallowing-upward environmental trend from a BA4 to an upper BA3 setting. We interpret this shallowing trend as a response to regional uplift. The initial existence of this deep-water association was likely facilitated by the unique paleogeographical position of the locality, which likely provided a stable habitat for this deep-water community. This study expands the known ecological range of the Xiushan Fauna and underscores the critical role of local paleogeography in shaping benthic community structures during the early Silurian.