Middle–Late Ordovician chitinozoans from the Yichang area, South China

Abstract

Chitinozoans from the Miaopo Formation (topmost Middle to lower Upper Ordovician) at Jieling, northern Yichang, western Hubei, were systematically studied, and 43 species of 16 genera were identified, which substantially increases the chitinozoan diversity of this particular time interval of the South China palaeoplate. Several key chitinozoan species from North Gondwana (e.g., Lagenochitina ponceti Rauscher) and Baltica (e.g., Laufeldochitina stentor (Eisenack) and Cyathochitina sebyensis Grahn) are reported for the first time in China. The chitinozoans of this formation are of late Darriwilian–early Sandbian age, and they have mixed North Gondwana and Baltica palaeogeographic affinities. The recognition of L. stentor, Armoricochitinagranulifera and C. sebyensis guarantees a better biostratigraphic correlation between South China and Baltica. Most of the formation, except for its topmost part, is assigned to the L. stentor Biozone, which can be further subdivided into two subzones: the Cyathochitina megacalix sp. nov. Subzone (lower) and the A. granulifera Subzone (upper). Three new species are formally described: C. megacalix sp. nov., Cyathochitina raricostata sp. nov. and Eisenackitina tenuis sp. nov.