LATE ORDOVICIAN TRILOBITE FAUNA AND SUCCESSION, YICHANG, HUBEI PROVINCE, CHINA

The new material described in this paper was collected from two measured sections through the Puxihe Member and Linxiang Member of the late Ordovician Pagoda Formation at Huanghuachang and Puxiheqiao, Yichang County (Text-figs. 1-3), including 31 trilobite species assigned to 22 genera and 1 subgenus. Among them one genus and two species are new, viz., Pentacopyge puxiheensis gen. et sp. nov. and Lamproscutellum? limbatus sp. nov., and following 11 forms are recorded for the first time in the Yichang area: Amphitron sp. 1, A. sp. 2, Cyclopyge recurva Lu, Decoropro-etus sp., Dislobosaspis guizhouensis (Yin), Madygenia snavis Petrunina, Microparia (Microparia) cf. speciosa (Hawle and Corda), Ovalocephalus kanlingensis (Zhang), O. yichongqiaoensis (Wu and Xia), Paraphillipsinella nanjiangensis Lu, Trinodus cylindricus Chen. The species Remopleurides amphitryonoides Lu, 1975 that was reassigned by Nikolaisen (1982) to the genus Sculptella Nikolaisen is here considered as a real member of Remopleurides on the basis of characters of the associate librigena, hypstome, thorax and pygidium. Except for the well-known Nankinolithus As semblage Zone (early Ashgill) that represents the uppermost horizonsof the Linxiang Member, no other reliable trilobite zones has been established for the Pagoda Formation in the Yichang area before. Four new additional remopleuridids-based biozones are, therefore, here suggested for the main part of the Pagoda Formation, in ascendingorder, the Pentacopyge puxiheensis Interval Zone, Hexacopyge yichangensis Interval Zone, Remopleurides amphitryonoides Range Zone (middle Caradoc:Puxihe Member),and the Dislobosaspis guizhouensis Range Zone(late Caradoc: lower part of the Linxiang Member).

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Clc Number:

Q915.819.1 P534.42