The Devonian-Carboniferous Boundary in Shallow-Water Facies Areas of China as Based on Conodonts

Traditionally, the lower boundary of the Aikuanian(Yanguanian) Stage has always been considered as the lower boundary of the Carboniferous in China. marked by the occurrence of the coral Cystophrentis.In recent years, some biostratigraphical research results have shown that the Cystophrentis zone is only distributed in the lower part of the Menggong’ao Formation(or the Gelaohe Formation) and that there is an interval zone namely the Cystophrentis-Pseudouralinia interval zone, wedged in just between the Cystophrertis zone and the Pseudouralinia zone in the upper part of the Menggong’ao Formation(or the GelaoheFormation). According to the current study of the conodont biostratigraphy, the coral Cystophrentis zone appears to be of latest Devonian age. So the lower boundary of the Aikuanian Stage is much lower than the lower Devonian-Carboniferous boundary and should no longer be regarded as the lower boundary of the Carboniferous in China. In this paper, two proposals for the Devonian-Carboniferous boundary in the shallow-water facies areas of China are put forward: 1) that the boundary is marked by the first appearance of the conodont Siphonodella(Eosiphonodella) simplex, and 2) that the boundary is recognized by the extinction of the coral Cystophrentis or the brachiopod Tenticospirifer.In addition, 4 species are newly estabished here: Icriodus obovatus sp. nov., Polygnathus lepidus sp. nov., Polygnathus paucidentatus sp. nov. and Polylophodonta jianghuaensis sp. nov.