Vertebrata Palasiatica ›› 2014, Vol. 52 ›› Issue (4): 381-389.
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SHANG Qing-Hua, LIU Jun, XU Guang-Hui, WANG Li-Ting
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尚庆华, 刘 俊, 徐光辉, 王立亭
Abstract: The holotype of Kwangsisaurus orientalis Young, 1959 is the only Triassic marine reptile specimen known from Guangxi Zhuang Autonomous Region in southern China. This fossil was collected from Wuming County in 1950s. The exact provenance of the specimen is unclear, but it has long been regarded as an Early Triassic sauropterygian following Young’s original description (Li, 2006b; Li et al., 2008; Zhao et al., 2008). The uncertainty regarding its age has introduced confusion into the studies of biogeography and evolutionary history of Chinese Triassic sauropterygians. Based on recent field work and the help of several local geologists who have knowledge of the specimen’s history, we have determined that the holotype of K. orientalis was from a quarry situated 2 km southeast of Fupeng, Suliang Village, Xianhu Township, Wuming County (Fig. 1). The type specimen was obtained from a fossiliferous bed within thin-bedded marlite, which is considered as the lower part of the Banna Formation based on lithological features. This fossiliferous bed contains abundant ammonites such as Balatonites, Protrachyceras, and Leiophyllites, in addition to some fragmentary vertebrate bones and plant debris (Figs. 1, 2). It can be identified as Middle Triassic based on the ammonites. Above it lies a tuff layer with a thickness of 10-20 cm, which is a marker bed of the Banna Formation. The tuff layer was dated to (244.2±0.7) Ma by High-precision SIMS zircon U-Pb analyses, making the age of K. orientalis Pelsonian (Anisian, Middle Triassic). The Anisian age of K. orientalis is concordant with its reidentification as a pistosaurid by Rieppel (1999a). This age assignment also refutes the longstanding interpretation that sauropterygians appeared in the Youjiang Basin during the Early Triassic, and shows instead that K. orientalis is almost synchronous with the Panxian marine reptile fauna. The Chinese record of sauropterygians shows that this group had dispersed over a large area and adapted to a diverse range of environments by the Anisian.
摘要: 广西武鸣产出广西地区迄今唯一一件三叠纪海生爬行动物化石——东方广西龙(Kwangsisaurus orientalis)。受限于20世纪50年代研究条件,有关该化石产出地点、地层层位和时代信息一直比较模糊,对后人阐述中国三叠纪海生爬行动物演化过程及探究鳍龙类在华南的古地理迁移历史造成了一定阻碍。本文从岩石地层学和生物地层学入手,结合高精度同位素年代学定年结果,对武鸣地区早、中三叠世地层进行了综合分析,着重研究了含东方广西龙地层的岩性组合、生物群面貌及地层时代。东方广西龙产于板纳组薄层泥晶灰岩中,伴生有丰富的菊石化石,所属地层时代为中三叠世安尼期。对含东方广西龙地层上部层状凝灰岩中具有岩浆韵律的锆石进行了SIMS原位U-Pb年代学测试,获得了(244.2±0.7) Ma的绝对年龄值,时代相当于安尼期中晚期。东方广西龙时代的厘定排除了鳍龙类早三叠纪世晚期在下扬子区和右江盆地同时出现的原有结论,同时同位素年代学新证据证实广西武鸣海生爬行动物化石与贵州盘县海生爬行动物群基本同期,表明了鳍龙类在华南东部起源后在三叠纪中期向西南地区辐射扩散范围的广阔性和适应环境的多样性。
SHANG Qing-Hua, LIU Jun, XU Guang-Hui, WANG Li-Ting. The age of Triassic marine reptile Kwangsisaurus orientalis (Sauropterygia) from Wuming, Guangxi, China. Vertebrata Palasiatica, 2014, 52(4): 381-389.
尚庆华, 刘 俊, 徐光辉, 王立亭. 2014, 52(4): 381-389, 论广西武鸣三叠纪海生爬行动物东方广西龙(鳍龙类)的时代. 古脊椎动物学报.
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https://www.vertpala.ac.cn/EN/Y2014/V52/I4/381