Jiangxigraptus Yu and Fang 1966 from the Upper Ordovician of southern Hunan Province

During the Late Ordovician, the southern part of Hunan Province was a depression basin, which recorded a continuous Sandbian-Katian biostratigraphic sequence of graptolitic shales. Herein we conduct a biostratigraphic study of the graptolites, mainly focusing on the genus Jiangxigraptus from the Shuangjiakou B section of Qidong County, Hunan Province. Based on the latest taxonomic classification scheme, six species are recognized, including Jiangxigraptus alabamensis (Ruedemann), Jiangxigraptus divaricatus (Hall), Jiangxigraptus gurleyi (Lapworth), Jiangxigraptus intortus (Lapworth), Jiangxigraptus sextans (Hall) and Jiangxigraptus vagus (Hadding). Moreover, this paper also discusses the palaeogeographic distribution of Jiangxigraptus. The results show that Jiangxigraptus is of critical importance in recognizing the Sandbian-Katian strata. Therefore, menmbers of this genus are suggested as auxiliary index for the biostratigraphic correlation of the base of the Upper Ordovician in regions such as South China

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