Productoid brachiopods from the Devonian (Famennian) Gelaohe and Car-boniferous (Tournaisian) Tangbagou formations of the Dushan area of Gui-zhou, China
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Abstract:
Ten species belonging to eight genera of productoid brachiopods (including indeterminate species) from the Upper Devonian Gelaohe and Lower Carboniferous Tangbagou formations in the Dushan area of Guizhou Province were described in this paper. The Gelaohe Formation contains Productella? sp., Yanguania dushanensis, Xinshaoproductus xinshaoensis and X. quadrata. Apart from sharing Productella? sp., Yanguania dushanensis, and Xinshaoproductus xinshaoensis with the Gelaohe Formation, the Tangbagou Formation also yields Hunanoproductus hunanensis, Spinocarinifera qilinzhaiensis sp. nov., Yanguania? sp., Tomiproductus sp., Ozora? sp., and Ericiatia kiangsuensis. The productoid brachiopods of these two formations are dominated by elements of the family Productidae (super-family Productoidea) in composition, and have only one representative of the family Productellidae and one of the family Sentosiidae (super-family Echinoconchoidea). Hunano-productus and Xinshaoproductus are first recognized in southern Guizhou in this study, and the former is preserved in a lower horizon than that in central Hunan Province. The Lower Carboniferous Tangbagou Formation in southern Guizhou witnesses the latest occurrence of Productella, which was previously recorded from Givetian to Frasnian of Eurasia and Up-per Devonian of Central Hunan. Spinocarinifera are widely recorded from Tournaisian or Tournaisian to Visean of Eurasia, North America, western Australia, and northern Africa. The new species S. qilinzhaiensis sp. nov. established herein, charac-terized by round quadrate outline, relatively short hinge line, small and flat ears, and weak but complete ribbings, is the only representative of the genera in South China. The spatial-temporal distribution of Tomiproductus generally accords with that of Spinocarinifera abroad, while in South China, Tomiproductus was recorded in the Liujiatang Formation of central Hunan and the Jinling Formation of Lower Yangtze area. The Ozora in southern Guizhou, if classified correctly, is the lowermost occurrence of the genus, lower than the records in the lower Visean of Missouri, US, and the Lower Carboniferous of South Mexico. The productids in southern Guizhou have a relatively low biodiversity in the Upper Devonian Gelaohe Formation, mainly comprising endemic genera such as Yanguania and Xinshaoproductus. The composition of productids in southern Guizhou was obviously affected by the Tournaisian transgression. Several cosmopolitan genera, including Spinocarinifera, Tomiproductus, Ozora, appeared in the Lower Carboniferous Tangbagou Formation this area, accompanied by the long-endurance endemic genera from the Gelaohe Formation, and thus obviously increased the biodiversity. Meanwhile, the biogeographical affinity among southern Guizhou, central Hunan, and Euramerica became closer due to the Tournaisian transgression in southern China.
