北海道上部白亜系産Gabbioceras属アンモナイトについて The genus Gabbioceras(Ammonoidea,Gaudryceratidae)from the Upper Cretaceous of Hokkaido,Japan
Two species of Gabbioceras HYATT, 1900 (Ammonoidea, Gaudryceratidae), Gabbioceras yezoense sp. nov. and G. mikasaense sp. nov. are described from the Upper Cretaceous of Hokkaido, northern Japan. G. yezoense sp. nov. occurs in the lower part of the lower Cenomanian. G. mikasaense sp. nov. occurs in the lower to the middle part of the lower Cenomanian and represents a yonger member of the Gabbioceras lineage. Although Gabbioceras experienced a dstinct decline from the late Albian and became extinct in the Mediterranean Tethyan realm, the occurrences reported here suggest that a few species of Gabbioceras survived and evolved in the Northwest Pacific region during the early Cenomanian.
- Bulletin of the National Science Museum Ser. C Geology & Paleontology
Bulletin of the National Science Museum Ser. C Geology & Paleontology 22(1・2), 1-9, 1996-06