The extinct river shark Glyphis pagoda from the Miocene of Myanmar and a review of the fossil record of the genus Glyphis (Carcharhiniformes: Carcharhinidae)

Kenshu Shimada, Naoko Egi, Takehisa Tsubamoto, Maung-Maung, Thaung-Htike, Zin-Maung-Maung-Thein, Yuichiro Nishioka, Teppei Sonoda, Masanaru Takai

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3 Citations (Scopus)

Abstract

We redescribe an extinct river shark, Glyphis pagoda (Noetling), on the basis of 20 teeth newly collected from three dif-ferent Miocene localities in Myanmar. One locality is a nearshore marine deposit (Obogon Formation) whereas the other two localities represent terrestrial freshwater deposits (Irrawaddy sediments), suggesting that G. pagoda from the Irrawad-dy sediments was capable of tolerating low salinity like the extant Glyphis. Glyphis pagoda likely reached up to at least 185 cm in total body length and was probably piscivorous. The fossil species occurs in rocks of Myanmar and eastern and western India and stratigraphically ranges at least from the Lower Miocene (Aquitanian) to the lower Upper Miocene (mid-Tortonian). It has been classified under at least eight other genera to date, along with numerous taxonomic synonyms largely stemming from the lack of understanding of the heterodonty in extant Glyphis in the original description. Our lit-erature review suggests that known Miocene shark faunas, particularly those in India, are manifested with unreliable tax-onomic identifications and outdated classifications that warrant the need for a comprehensive taxonomic review in order to evaluate the evolutionary history and diversity pattern of Miocene shark faunas. The genus Glyphis has a roughly 23- million-year-long history, and its success may be related to the evolution of its low salinity tolerance. While extant Glyphis spp. are considered to be particularly vulnerable to habitat degradation and overfishing, the fossil record of G. pa-goda provides renewed perspective on the natural history of the genus that can be taken into further consideration for con-servation biology of the extant forms.

Original languageEnglish
Pages (from-to)237-251
Number of pages15
JournalZootaxa
Volume4161
Issue number2
DOIs
Publication statusPublished - 2016 Sep 5

Keywords

  • Chondrichthyes
  • Elasmobranchii
  • Fossil
  • Irrawaddy sediments
  • Obogon format

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Animal Science and Zoology

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    Shimada, K., Egi, N., Tsubamoto, T., Maung-Maung, Thaung-Htike, Zin-Maung-Maung-Thein, Nishioka, Y., Sonoda, T., & Takai, M. (2016). The extinct river shark Glyphis pagoda from the Miocene of Myanmar and a review of the fossil record of the genus Glyphis (Carcharhiniformes: Carcharhinidae). Zootaxa, 4161(2), 237-251. https://doi.org/10.11646/zootaxa.4161.2.6