Age of the Early Triassic Ichthyopterygian Thaisaurus Inferred from Ammonoid Biostratigraphy

DOI 1 Citations 13 References
  • Kittichai Tongtherm
    Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Ten-nodai, Tsukuba, Ibaraki 305-8572, Japan (e-mail: tongtherm@gmail.com)
  • Yasunari Shigeta
    Department of Geology and Paleontology, National Museum of Nature and Science, 4-1-1 Amakubo, Tsukuba, Ibaraki 305-0005, Japan
  • Apsorn Sardsud
    Mineral Resources Research and Development Center, Department of Mineral Resources, 75/10 Rama VI Road, Ratchatewi, Bangkok 10400, Thailand
  • Katsuo Sashida
    Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Ten-nodai, Tsukuba, Ibaraki 305-8572, Japan (e-mail: tongtherm@gmail.com)
  • Sachiko Agematsu
    Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Ten-nodai, Tsukuba, Ibaraki 305-8572, Japan (e-mail: tongtherm@gmail.com)

Description

The age of the primitive ichthyopterygian Thaisaurus is more accurately defined due to the discovery of a new species of the ammonoid genus Marcouxia from beds about 2.4 m below the horizon from which the holotype of Thaisaurus chonglakmanii was collected in the Phukhaothong Dolomite Member of the Chaiburi Formation in the Phatthalung area, southern Thailand. The shell of Marcouxia chaiburiensis sp. nov. is characterized by a quadrate whorl section, an arched venter with a sub-acute keel-like elevation, and spiny tubercles on the ventrolateral shoulders as well as numerous regularly spaced, radial or slightly prorsiradiate ribs. Because the range of Marcouxia is limited to the Columbites parisianus Subzone of the lower Spathian (upper Olenekian, Lower Triassic) in the western USA, the age of Thaisaurus is likely constrained to the early Spathian, thus suggesting it is one of the oldest known ichthyopterygians.

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Details 詳細情報について

  • CRID
    1360848663997903232
  • NII Article ID
    210000158547
  • DOI
    10.2517/2019pr022
  • ISSN
    13428144
  • Data Source
    • Crossref
    • CiNii Articles
    • KAKEN
    • OpenAIRE

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