Guadalupian (Middle Permian) giant bivalve Alatoconchidae from a mid-Panthalassan paleo-atoll complex in Kyushu, Japan: A unique community associated with Tethyan fusulines and corals

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Unique new fossil assemblages containing the large bivalve family Alatoconchidae are recorded from the Guadalupian (Middle Permian) shallow marine limestone in Kamura, Kyushu. The large bivalves occur in the <i>Neoschwagerina</i> Zone and <i>Lepidolina</i> Zone. This discovery establishes that the biostratigraphic range of the family Alatoconchidae extends up to the top of the <i>Lepidolina</i> Zone (upper Capitanian of upper Guadalupian) i.e., to the end-Guadalupian extinction level. The largest Alatoconchidae in Kamura occurs in the <i>Neoschwagerina</i> Zone, the size of which is up to 50 cm long and 5 cm thick. Although details are still unknown, their morphology with a wing-like side projection of their valves appears very similar to that of Alatoconchidae that includes the well-known genus <i>Shikamaia</i> Ozaki. The bivalve-bearing Iwato Formation was derived from a mid-oceanic shallow marine carbonate build-up formed on a mid-oceanic paleo-seamount. The close association among the Alatoconchidae, typical Tethyan fusulines (Verbeekinidae) and rugose corals (Waagenophyllidae), plus their common extinction pattern suggests that the Alatoconchidae flourished in warm, shallow (photic) marine environments in low latitude areas in Panthalassa as well as Tethys. The extra-large size and double-layered shell with a translucent outer layer composed of prismatic calcite suggests that these bivalves may have hosted abundant photosynthetic algal symbionts to support their large-body metabolism.<br> <br> <br> (Communicated by Tatsuro MATSUMOTO, M.J.A.)<br>


  • Proceedings of the Japan Academy, Series B

    Proceedings of the Japan Academy, Series B 82(1), 25-32, 2006

    The Japan Academy

Cited by:  3


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    Journal Article
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    ZS8(科学技術--医学--解剖学・生理学・生化学) // ZR1(科学技術--生物学)
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    CJPref  NDL  J-STAGE 
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