Recent progress in the research on the Sinian conodonts from the western margin of the Yangtze platform

The Silurian lithostratigraphy and conodont biostratigraphy are focused for the Ninglang-Yanbian region on the western margin of the Yangtze platform. Three assemblage zones have been discriminated: Panderodus gracilis-Panderodus simplex, Pterospathodus celloni-Walliser and-Pterospathodus amorphognathoides-Walliser zones. The strata in this region are redivided on the basis of biostratigraphy, sedimentology and regional correlation, and some important genera are described in detail. The study of the interrelations shows that there is a gradational rather than sharp contact between the-Pterospathodus celloni-Walliser and-Pterospathodus amorphognathoides-Walliser zones.