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

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    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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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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  • Received:February 25,2019
  • Revised:September 22,2019
  • Adopted:December 05,2019
  • Online: December 05,2019
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