The cephalopod Sinoceras chinense (Foord) is regarded as the index fossil of the Upper Ordovician Pagoda Formation on the Yangtze Platform of South China, with a likely age of early Katian. S. chinense was previously only known from the Upper Ordovician of Chinese blocks/terranes, including South China, Tarim, Tibet (Xizang) and western Yunnan.
During January 2020, an international research team lead by Dr. FANG Xiang from Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (NIGPAS), and Prof. Clive BURRETT from Mahasarakham University conducted a Sino-Thai joint field trip in western Thailand. During the fieldwork, the first identification of S. chinense is confirmed. This work has been published online in Palaeoworld.
These specimens were recorded in a geoconservation named “Nautiloid Site”, located in Si Sawat county of Kanchanaburi Province, western Thailand. Previously, these specimens were wrongly identified as actinocerids, which results in the misjudgments on geological time of the upper part of Tha Manao Formation. The exact identification of S. chinense suggests the upper part of Tha Manao Formation age of early Katian of Late Ordovician, providing evidence for the stratigraphic correlation between the upper part of the Tha Manao Formation in Thailand and the Pagoda Formation (and contemporaneous units) in China.
Western Thailand, combined with Baoshan region of western Yunnan, was located on Sibumasu Terrane during the Early Palaeozoic. The confirmed identification of S. chinense in Thailand is the first record in Thailand and alsothe first report in a region outside of China.Moreover, the discovery of the species in the Sibumasu Terrane provides strong support for the palaeogeographic reconstruction and pronounced palaeobiogeographic changes from the Middle to Late Ordovician among the peri-Gondwanan regions.
This research has been supported by CAS Strategic Priority Research Program, The Second Tibetan Plateau Scientific Expedition and Research, State Key Laboratory of Palaeobiology and Stratigraphy, Ministry of Nature and Resources of China, and Mahasarakham University.
Reference: Fang, X., Li, C., Li, W.J., Burrett, C., Udchachon, M., Zhang, Y.D., 2020. Sinoceras chinense (Foord, 1888) in western Thailand: first identification outside China. Palaeowolrd. https://doi.org/10.1016/j.palwor.2020.06.004
Sinoceras chinense, collected from Si Sawat county of Kanchanabura Province, western Thaialand
Distribution of S. chinense in the northeastern peri-Gondwana region