加拿大北极地区泥盆纪叶肢介修订及兼论早期李氏叶肢介类(leaiins)的形态特征

湘南地区在晚奥陶世发育深水坳陷盆地相沉积, 完整记录了晚奥陶世桑比–凯迪期笔石页岩相生物地层序列。本论文在湘南地区祁东双家口 B 剖面开展笔石化石系统采集和生物地层学研究, 针对特征的江西笔石 (Jiangxigraptus)开展研究, 根据最新的分类学方案鉴定出江西笔石 1 属 6 种, 包括 Jiangxigraptus alabamensis (Ruedemann)、 Jiangxigraptus divaricatus (Hall)、 Jiangxigraptus gurleyi (Lapworth)、 Jiangxigraptus intortus (Lapworth)、Jiangxigraptus sextans (Hall)和 Jiangxigraptus vagus (Hadding)。此外, 本文还讨论了该属在全球范围内的分布, 认为在华南等地, Jiangxigraptus 可作为全球上奥陶统底界笔石生物地层对比的辅助属, 对识别上奥陶统桑比–凯迪阶的地层具有重要意义。

Revision of the Devonian clam shrimp (Diplostraca: Spinicaudata) from the Canadian Arctic and discussion on the early morphotypes of the leaiins

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