Devonian Rugose Coral Biostratigraphy of China: Assemblage Sequences, Extinction-Recovery Cycles and Global Correlation

Devonian rugose corals are among the most diagnostic benthic fossils for regional and global biostratigraphic subdivision and correlation. Based on extensive investigations of sections across South China, this study establishes a complete Devonian rugose coral biostratigraphic framework spanning the Lochkovian to Famennian stages, integrating taxonomic, assemblage, and extinction–recovery data. The Early Devonian (Lochkovian) coral fauna retains strong Silurian affinities, dominated by the Carlinastraea assemblage widely distributed in Yunnan, Jilin, and Inner Mongolia. Typical Devonian coral lineages initiated their major diversification in the Pragian and accelerated through the Emsian, as evidenced by the appearance of calcicolous rugosans such as Calceola during the late Emsian (Wright et al., 2025). The Middle Devonian (Givetian) marks the acme of diversification, peaking in the middle Givetian but beginning as early as the Eifelian. Two key assemblages—the Truncicarinulum liujingense–Planocoenites guilinensisAssemblage (platform–basin transition) and the Endophyllum Assemblage (shallow carbonate platforms)—serve as critical markers for the Middle–Upper Devonian boundary. South China records 97 Givetian reef sites, with three ecological associations (open-marine stromatoporoid-coral frameworks, back-reef/lagoonal branching stromatoporoids, and microbial thrombolites) and six high-resolution development stages (Earth-Science Reviews, 2025). The mid-Givetian Kačák event caused a temporary decline in coral diversity, followed by a rapid recovery. The Late Devonian (Frasnian) witnessed high-diversity colonial rugose corals as one of the major reef-builders, but the Frasnian–Famennian mass extinction—which occurred in three distinct steps sequentially affecting brachiopods, conodonts, and benthic faunas—eliminated nearly all platform-dwelling rugose coral taxa, with only 2–3 genera surviving in South China. The Early Famennian represents a prolonged survival interval with extremely low diversity in South China, whereas the Hongguleleng Formation of North Xinjiang acted as a unique refugium, preserving abundant and diverse post-extinction corals. In contrast, the early Famennian of southern Belgium and southern France records a slow but persistent recovery, highlighting regional heterogeneity in post-extinction patterns. The Late Famennian (Strunian) recovery was temporally and spatially complex: in most of South China, small, simple solitary corals (Cystophrentis, Cyathaxonia faunas) dominated, but the Changtanshan section (Longmenshan area) records a last flourishing of stromatoporoids and tabulate corals just prior to the early Hangenberg Crisis, followed by the final extinction at the Hangenberg event. The appearance of Cyathaxonia faunas in the Late Famennian does not solely indicate a weak recovery; these faunas are widespread in Permian deep-water settings and achieved much higher diversity in the Early Carboniferous. The Devonian–Carboniferous boundary (DCB) in South China remains debated; recent studies suggest the DCB lies above the top of the Cystophrentis Zone, with possible sedimentary hiatuses. The Changtanshan section provides a rare high-resolution record of coral turnover across the DCB transition. Biogeographically, Chinese Devonian rugose corals are not uniformly assigned to the Old World Realm. The four low-latitude regions (South Tianshan, Paleo-Tethys, South China, and northern margin of North China) belong to the Old World Realm, whereas the Junggar-Xing'an and Baoshan regions were situated in the north-temperate and south-temperate zones, respectively, and lie outside the Old World Realm. The South China Block, with its unique three-dimensional paleogeography of inland sea–platform–intraplatform basin, served as a key reef-building hotspot in the eastern Paleo-Tethys. This biostratigraphic framework clarifies coral turnover across three critical boundaries (Silurian–Devonian, Middle–Late Devonian, Devonian–Carboniferous) and provides robust constraints for Devonian chronostratigraphy, sea-level fluctuations, and global extinction dynamics.