Silicified rhynchonelliform brachiopods from the kuniutan formation (Darriwilian: Middle ordovician), Guiyang, South China

Abstract

A silicified brachiopod fauna from the Middle Ordovician Kuniutan Formation (lower-middle Darriwilian, i.e. uppermost Arenig to lower Llanvirn) at Wudang, Guiyang, central Guizhou, South China, includes abundant specimens of Yangtzeella, Orthambonites and Leptellina together with common Parisorthis, Saucrorthis, rare Anomalorthis?., Hemipronites?., Leptestia?. and, significantly, Aporthophyla; associated are rare trilobites, gastropods, crinoids and nautiloids. The Yangtzeella kueiyangensis-Orthambonites delicata Association is defined for this shallow-water, Benthic Assemblage 3, association. This first record of Aporthophyla in South China may indicate a link between South China and the Toquima-Table Head Province, where the Aporthophyla fauna is more typically developed. However, this association is significantly different from the latter in having three endemic genera, Yangtzeella, Saucrorthis and Parisorthis, rare numbers of Aporthophyla and Anoma lorthisl, and the absence of many other typical elements of the Aporthophyla fauna. The occurrence of Orthambonites, Hemipronitesl and Leptestia? suggests some relationships between South China and the Baltic Platform during the Mid Ordovician. The various brachiopod associations bearing Aporthophyla may be quite different in nature, composition and diversity, and may possess different background palaeobiogeographical signatures. The assemblages containing Aporthophyla in South China, Qaidam, Malaysia, Australia and possibly Tibet are clearly different biogeographically from those associated with the Toquima-Table Head and the Celtic provinces. Two new species, Aporthophyla sinensis sp. nov. and Leptellina orientalis sp. nov. are described. © The Palaeontological Association.