湖北早三叠世鱼龙前肢化石新材料及对比讨论
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本文为湖北省地质局科技项目(编号KJ2018- 02)、湖北省地质勘查基金项目(编号DTCG- 190401)、国家自然科学基金项目(编号41402005&41972014)和中国地质调查局地质调查项目(编号DD20190823)资助。


New forefin specimens and comparison of Early Triassic Ichthyopterygia from the Hubei Province
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    摘要:

    杨钟健和董枝明曾在1972年指出中国发现的早三叠世鱼龙Chaohusaurus geishanensis与欧洲的Grippia前肢和头部相似,具有系统关系。但后来中国该时代鱼龙类化石大多前肢特化或不完整,难以进一步对比研究。本文记述了湖北下三叠统嘉陵江组中发现的2件较完整的鱼龙前肢化石新材料,对中国的古老鱼龙类相关信息进行了补充。通过形态学对比,认为湖北被归入Chaohusaurus的早三叠世鱼龙前肢总体特征与同属的Chgeishanensis接近而与Chchaoxianensis有明显差别,而且其以相对较大的个体、间中骨挤压变形以及豌豆骨发育等特征表现出与Grippia、Utatsusaurus、Parvinatator等其他早三叠世鱼龙类前肢的相似性。据此分析推测,早三叠世鱼龙类可能存在两个演化方向。即在二叠纪末大灭绝(EPME)事件后不久,鱼龙类起源并在奥伦尼克期出现分化,一部分个体相对较大、前肢未特化、运动能力较强的鱼龙类实现了跨区交流,另一些个体相对较小、前肢特化、运动能力较弱的鱼龙类则成为地方性(东特提斯区)的独立演化分支。但两者之间的系统发生关系以及Chaohusaurus的单系性还有待进一步研究揭示。

    Abstract:

    Chaohusaurus geishanensis, an Early Triassic ichthyopterygia found in China, shares similar forefin and skull structures and reveals a systematic relationship to Grippia in Europe. However,further intercomparison was difficult because specimens subsequently discovered in China were either highly specialized in forelimb or incomplete. Here, two nearly complete and non—specialized forelimbs of Chaohusaurus found in the Lower Triassic Jialingjiang Formation in Hubei Province are described with related information on basal ichthyopterygians in China. Morphological comparison reveals that the general features of the Early Triassic Chaohusaurus in the Hubei Province were close to Ch. geishanensis of the same genus, but distinctly different from Ch. chaoxianensis. Its features such as relatively large individual size, intermediate squeezing and deformation and pisiform development shares some similarities with Grippia,Utatsusaurus,Parvinatator and other Early Triassic ichthyopterygians. Based on these results we propose that there were possibly two directions for evolution of the Early Triassic ichthyopterygians. After the end- Permian mass extinction (EPME), ichthyopterygians appeared and soon differentiated during the Olenekian. Some large individuals without specialized forelimbs but with strong motor ability migrated between different regions. However, other small individuals with specialized forelimbs and weak motor ability became a local (eastern Tethys) independently evolving branch. However,the clarification of the phylogenetic relationship between them, and the monophyly of Chaohusaurus needs to be tested by future studies.

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邹亚锐,赵璧,陈刚,李姜丽,程龙,阎春波,谭秋明.2020.湖北早三叠世鱼龙前肢化石新材料及对比讨论[J].地质学报,94(4):1017-1026.
ZOU Yarui, ZHAO Bi, CHEN Gang, LI Jiangli, CHENG Long, YAN Chunbo, TAN Qiuming.2020. New forefin specimens and comparison of Early Triassic Ichthyopterygia from the Hubei Province[J]. Acta Geologica Sinica,94(4):1017-1026.

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  • 收稿日期:2019-02-25
  • 最后修改日期:2019-09-22
  • 录用日期:2019-12-05
  • 在线发布日期: 2019-12-05