Abstract

A silicified brachiopod assemblage living between the first and second episodes of latest Ordovician mass extinction is first described from micritic bioclastic limestone of Kuanyinchiao Bed, northwestern Guizhou, southwest China. It contains six species, Dalmanella testudinaria (Dalman, 1828), Plectothyrella crassicosta (Dalman, 1828), Hindella crassa incipiens (Williams, 1951), Eostropheodonta sp., the characteristic constituents of the Hirnantia fauna, and two new species, Fardenia modica and Dorytreta longicrura. It lacks Hirnantia, Kinnella, Cliftonia, and Paromalomena, the other characteristic elements of the Hirnantia fauna. A new, low diversity community (inner BA3) dominated by brachiopods is proposed as the Dalmanella testudinaria-Dorytreta longicrura Community along with the trilobite Dalmanitina nanchengensis Lu, rugose corals, and gastropods. Composition of this community of the Hirnantia fauna was controlled primarily by temperature, water depth, and substrate. Comparison with other communities of the Hirnantia fauna in south China supports this conclusion. Fluctuations in generic composition of the Hirnantia fauna and the related factors are also discussed.

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