The Edgewood–Cathay (EC) brachiopod fauna, typified by Cathaysiorthis, is an important fossil assemblage for recognizing the survival to early recovery interval following the Late Ordovician mass extinction (LOME). It records the persistence of surviving “Ordovician-type” groups, the emergence of new taxa, and the reorganization of benthic communities after the disappearance of the Hirnantia Fauna. It is therefore of considerable significance for understanding brachiopod macroevolution and palaeobiogeographical patterns across the Ordovician–Silurian transition.
Recently, SHI Kaiyan, a master’s student at the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (NIGPAS), under the supervision of Prof. HUANG Bin and in collaboration with Prof. RONG Jiayu and Prof. ZHAN Renbin, reported for the first time an EC Fauna from the Wulipo Bed in Meitan, Guizhou Province. The result was published in Palaeoworld.
A total of 1,224 brachiopod specimens were obtained, representing 13 species in 13 genera. The fauna is dominated by Eospirigerina, Hindella, and Cathaysiorthis (Fig. 1). Non-metric Multidimensional Scaling (NMDS) and network analyses show that the northern Guizhou EC Fauna is closely related to the typical EC faunas of eastern China but is clearly distinct from the Hirnantia Fauna (Fig. 2). This discovery extends the known distribution of the early EC Fauna to the southwestern margin of the Yangtze Platform.
Within this fauna, “Ordovician-type” clades, particularly Orthida and Strophomenida, remain dominant, while newly emerged taxa such as Cathaysiorthis are also present, indicating that the fauna belongs to the survival to early recovery interval following the mass extinction. Compared with the possibly younger Cathaysiorthis fauna from Xichuan, He’nan Province, in which the proportion of “Silurian-type” clades had increased, the northern Guizhou fauna represents an earlier stage of brachiopod-community recovery. It also provides new material for comparing regional differences among contemporaneous faunas from eastern China, northern Guizhou, and northeastern Yunnan.
The study also reassessed the relationships among the Wulipo Bed, Shiqian Formation, and Weiba Formation. “Wulipo Bed” is the earliest valid name applied to this lithostratigraphic unit. However, the name “Wulipo” had already been used for a Permian formation, resulting in a nomenclatural conflict. The Stratigraphic Lexicon of China: Permian System considers the Permian Wulipo Formation to represent the upper part of the Yangshan Formation and suggests that it should not be recognized as an independent formation. Moreover, the Compendium of Chinese Lithostratigraphic Nomenclature (National Stratigraphic Committee, 2017) lists both names. The present study therefore temporarily retains “Wulipo Bed” as a valid bed-rank unit.
Because the Shiqian and Weiba formations are each less than 4 m thick and are too thin to serve as mappable lithostratigraphic units, they are downgraded to the Shiqian Bed and Weiba Bed, respectively, and are regarded as junior subjective synonyms of the Wulipo Bed (Fig. 3). This revision helps to standardize the lithostratigraphic framework across the Ordovician–Silurian boundary in northern Guizhou and adjacent regions, providing a more stable basis for regional stratigraphic correlation and studies of biotic macroevolution.
The brachiopod fauna of the Wulipo Bed shows an upward succession from the Eospirigerina–Hindella Association to the Eospirigerina–Cathaysiorthis Association. The palaeoecological setting changes from Benthic Assemblage 2 (BA2) to Benthic Assemblage 3 (BA3), indicating progressive deepening of the water. This succession records a transgressive event after the second phase of the LOME and provides palaeoecological evidence for post-glacial warming, ice-sheet melting, and sea-level rise.
The study expands the known palaeogeographical range of the early Cathaysiorthis fauna and reveals the composition and ecological changes of the earliest recovery communities in the southwestern part of the South China plate. It also provides key new data for standardizing the regional stratigraphic framework and understanding the reorganization of benthic ecosystems after the mass extinction.
Reference: Kai-Yan Shi, Bing Huang*, Ren-Bin Zhan, Jia-Yu Rong. 2026. A new Edgewood-Cathay Fauna from the Wulipo Bed (uppermost Ordovician to lowermost Silurian) in South China and its palaeoecological significance. Palaeoworld 35, 201152. https://doi.org/10.1016/j.palwor.2026.201152.
Fig. 1. Representative taxa of the EC Fauna from northern Guizhou.
Fig. 2. Network analysis showing that the studied fauna is closely related to the EC faunas of eastern China but clearly distinct from the Hirnantia Fauna.
Fig. 3. The Shiqian Formation in the Shiqian area and the Weiba Formation in the Zhenxiong area, each less than 4 m thick, are revised as the Shiqian Bed and Weiba Bed and regarded as junior subjective synonyms of the Wulipo Bed.
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