山中地域の白亜系産頭足類

概要

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We describe seven ammonite species from the Cretaceous Ishido Formation of the Sanchu area in the Kwanto Mountains, including a new species and one nautiloid : Simbirskites (Milanowskia) sp., Barremites (B.) difficilis (D'ORBIGNY), and Pulchellia ishidoensis YABE et SHIMIZU from the lower part of the formation, Phylloceras sp., Shasticrioceras aff. S. patricki MURPHY, Barremites (B.) aff. B. strettostoma (UHLIG), Pseudohaploceras japonicum OBATA et MATSUKAWA sp. nov., and Heminautilus cf. H. lallierianus (D'ORBIGNY) from the upper part of the formation. Thus the lower part of the Ishido Formation is probably assignable to the Upper Hauterivian to the Lower Barremian, and the upper part of the formation to the upper Lower Barremian. Another ammonite species, Anagaudryceras cf. A. sacya (FORBES) from the upper member of the Sanyama Formation is described. The species is rather long-ranged, suggesting the Albian to the Cenomanian. These cephalopod species provide a basis for the detailed scheme of the Lower Cretaceous biostratigraphic zonation in Japan.
国立科学博物館の論文
1984-03-22