湖北早三叠世鱼龙前肢化石新材料及对比讨论  

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

作　　者：邹亚锐 赵璧 陈刚 李姜丽 程龙 阎春波[2,3] 谭秋明 ZOU Yarui;ZHAO Bi;CHEN Gang;LI Jiangli;CHENG Long;YAN Chunbo;TAN Qiuming(Hubei Institute of Geosciences,Wuhan,430038;Central South China Irmovation Center JorGeosciences,Wuhan,430205;Wuhan Center of China Geological Survey,Wuhan 430205)

机构地区：[1]湖北省地质科学研究院,武汉430034 [2]中南地质科技创新中心,武汉30205 [3]中国地质调查局武汉地质调查中心,武汉430205

出　　处：《地质学报》2020年第4期1017-1026,共10页Acta Geologica Sinica

基　　金：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);中国地质调查局地质调查项目(编号DD20190823)资助。

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。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.

关 键 词：湖北 早三叠世 嘉陵江组 鱼龙超目 前肢 

分 类 号：Q915.2[天文地球—古生物学与地层学]