上扬子区奥陶纪三叶虫属Hexacopyge的新材料

NEW MATERIAL OF THE TRILOBITE GENUS HEXACOPYGE FROM THE ORDOVICIAN OF THE UPPER YANGTZE REGION

描述上扬子区鄂西和湘西中及晚奥陶世桨肋虫类三叶虫Hexacopyge的 5个种 ,包括 2新种 ,即H .turbiniformis和H .yichangensis;讨论Hexacopyge的定义及其与相关属的关系。Hexacopyge在区内分布广、演化快 。

Since Yuan and Zhou (1998) erected the remopleuridid genus Hexacopyge , with Remopleurides nasutus Lu, 1957 as the type species, more forms of the genus have been reported from South China (Zhou et al. , 2000; Peng et al ., 2001; Zhou et al., 2001). The hypostome of Hexacopyge as described by Peng et al . (2001, pl. 2, figs. 4, 9, 10) has a tripartite but with no median boss, showing an additional important diagnostic character. New material from the Middle Upper Ordovician of the Upper Yangtze Region indicates that the morphology of species of Hexacopyge changed rapidly through the Middle and Late Odovician, and may have great potential in correlating the regional stratigraphy. Five species of which two are new are described in this paper. They are H. cf. nasuta (Lu, 1957) from the Xiaotan Formation (late Arenig) of Cheng kou, Chongqing; H. turbiniformis sp. nov. from the lower part of the Pagoda Formation (late Llanvirn early Caradoc) of Yichongqiao, Cili and Maocaopu, Taoyuan, Hunan; H. yichangensis sp. nov. from the Puxihe member (middle Caradoc) of the Pagoda Formation (Zhou et al., 1999) of Huanghuachang and Puxiheqiao, Yichang, Hubei; H. cf. yichangensis from the middle part of the Pagoda Formation (middle Caradoc) of Yichongqiao and Maocaopu; and H. sp. from the middle part of the Pagoda Formation (middle Caradoc) of Maocaopu (Text fig. 1).