Brachiopods from the Middle Ordovician Shihtzupu Formation of Yunnan Province, China

The brachiopod fauna of the Middle Ordovician (upper Darriwilian) Shihtzupu Formation in the Weixin area, northeastern Yunnan Province, southwestern China, comprises 16 genera and 18 species, including one new genus (Halirhachis) and five new species (Glyptorthis sarcina, Protoskenidioides weixinensis, Halirhachis leonina, Leptellina spatiosa, and Leptestiina veturna). Cluster and principal component analyses of the latest Arenigian–mid−Caradocian faunas of the Upper Yangtze Platform with selected faunas of similar age from other palaeoplates or terranes indicate that the Weixin brachiopods have closest faunal affinities to those of the typical Shihtzupu Formation in Guizhou Province and the Naungkangyi Group of Burma (Myanmar). During latest Arenigian–mid−Caradocian times, the brachiopods of the Upper Yangtze Platform, Sibumasu, and Chu−Ili palaeogeographical regions constituted a distinct faunal province, characterized by a large number of endemic taxa as well as regionally widespread genera such as Saucrorthis, Martellia, and Yangtzeella. This brachiopod faunal province has very low similarity coefficients with the coeval brachiopod faunas of Laurentia and Avalonia.