The Global boundary Stratotype Section and Point (GSSP) for the base of the Wuchiapingian Stage (Lopingian) is defined at the FAD of the conodont species Clarkina postbitteri postbitteri within the lineage from C. postbitteri hongshuiensis to C. dukouensis at the base of Bed 6k at the Penglaitan section. The section is located at 23°41’43”N, 109°19’16”E near Laibin City, Guangxi Province.
The GSSP at the Penglaitan Section