Conodont faunas across the Mid-Carboniferous boundary in the Hina Limestone, Southwest Japan
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概要
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The Hina Limestone yields abundant conodont elements that range from early Visean to late Bashkirian in age. These conodont faunas permit detailed examination of the successive changes across the Mid-Carboniferous boundary. Six conodont zones can be recognized in ascending order : the Gnathodus bilineatus, Declinognathodus inaequalis-Gnathodus bilineatus, Declinognathodus noduliferus, Neolochriea nagatoensis, Neolochriea koikei, and Neognathodus symmetricus Zones. The Mid-Carboniferous boundary in the Hina Limestone can be identified by the base of the Declinognathodus inaequalis-Gnathodus bilineatus Zone. A remarkable faunal transition occurs within the Declinognathodus inaequalis-Gnathodus bilineatus and Declinognathodus noduliferus Zones, in which Mississippian conodonts go extinct and several new typical Pennsylvanian taxa appear. Three Declinognathodus species, Declinognathodus inaequalis, D. noduliferus, and D. japonicus, successively appear in the order given. A new genus, Neolochriea, with Neolochriea hisaharui, sp. nov. as the type species and two other new species, N. hisayoshii and N. koikei, are described in addition to eight other species of conodonts. All Neolochriea species occur in the stratigraphic level between the extinction of Mississippian conodonts and the appearance of Neognathodus symmetricus.
- 日本古生物学会の論文
- 1997-12-30