Internal supporting structures of some Late Ordovician graptolites from South China revealed by micro-CT |
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| Authors: | Wenhui Wang Lucy A Muir Muhui Zhang Ran Zhao Jingqiang Tan Xu Chen |
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| Institution: | 1. Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring, Ministry of Education, School of Geosciences and Info-Physics, Central South University, Changsha, 410083 China;2. Department of Natural Sciences, Amgueddfa Cymru – National Museum Wales, Cathays Park, Cardiff, CF10 3LP UK;3. State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan, 430074 China;4. CAS Key Laboratory of Economic Stratigraphy and Palaeogeography, Nanjing Institute of Geology and Palaeontology, 39 East Beijing Road, Nanjing, 210008 China |
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| Abstract: | Three-dimensionally preserved pyritic internal moulds of the Late Ordovician graptolites Appendispinograptus leptothecalis and Styracograptus chiai from the Upper Ordovician Wufeng Formation of the Daheba section, Hunan Province, South China, were imaged by micro-CT. The distinctive pea-shaped pits/dimples aligned in a zigzag line arising from the second/third thecal pair on the tubarium in these species are interpreted as the surface expression of the junction between the lateral thecal walls and the thickened internal cross-bars that support the nema. The relations between different internal structures such as the nema, median septum, aboral lists, interthecal septa and cross-bars are summarized, and examples of these supporting systems in different taxa are illustrated. The presence of isolated cross-bars in different diplograptid tubarium may suggest that they have evolved as a result of constructional restrictions. |
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| Keywords: | Graptolithina Katian micro-CT pyritization South China systematics |
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