Graptolite biostratigraphy of the Shihtien Formation (Darriwilian) in West Yunnan, China

A rich mid-Ordovician graptolite fauna is reported from the Shihtien Formation at Baoshan and Shidian in West Yunnan Province, SW China. The fauna comprises Didymograptus artus, D. murchisoni, D. spinulosus, Pterograptus sp., Hustedograptus vikarbyensis, H. teretiusculus, Archiclimacograptus angulatus, A. riddellensis, Haddingograptus oliveri, Proclimacograptus angustatus, and dendroids such as Dictyonema, Ptilograptus, Dendrograptus, Callograptus, indicating an age of mid- to late Darriwilian. Based on the fauna, two graptolite assemblages are recognized, in ascending order, the Didymograptus artus and Didymograptus murchisoni biozones. The graptolite fauna shows a considerable similarity to those contemporary in Baltica and the Yangtze Region of South China.