大分県院内町産コイ科魚類咽頭歯化石

概要

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We excavated fossil cyprinids of the Late Pliocene Tsubusagawa Formation at 16 localities of Innai, Oita Prefecture, Northern Kyushu. We collected 2,468 fossil Pharyngeal teeth of cyprinids. They consist of six subfamilies, Leuciscinae, Cultrinae, Xenocypridinae, Rhodeinae, Gobioninae and Cypridinae. The fossils of cultrines contain three genera, Ischikauia, Megalobrama and Culler. Those of xenocypridines contain four genera, Xenocypris, Plagiognathopus, Distoechodon and Acanthobrama. The rhodeine fossil is of the genus Rhodeus, and the gobionine one is of the genus Squalidus. The cyprinine fossils consist of two genera, Cyprinus and Carassius. The fossils of the genus Carassius is dominant in the fossil assemblage, and they are followed by those of xenocypridine, which is an ectinct subfamily in Japan. This cyprinid fauna is a typical Plio-Pleistocene one in Japanese Islands. The compositions of the fossil fauna are changed in the horizen of the localities. The xenocypridine fossils account for 40.87% in the lower horizen, but they account for 8.8-14.5 % in the middle and upper horizen. On the other hand, the fossils of Carassius are increased in rate in the middle and upper horizen. This change of the composition of the fossils indicates that the lake became wide and deep.
地学団体研究会の論文
1991-05-25