上総・下総両層群(鮮新世〜更新世)から産したホホジロザメの歯化石

概要

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Six fossil teeth of the great white shark, Carcharodon carcharias, from five localities of the Boso Peninsula and Shimosa Upland are described. Results are summarized as follows. 1) The horizons which occured the fossil shark teeth are the Kurotaki and Ichijiku Formations of the Kazusa Group, and the Jizodo and Narita Formations of the Shimosa Group. The geological age ranges from the Pliocene to the Upper Pleistocene. 2) Comparing with the teeth of the Recent Carcharodon carcharias, these fossil teeth are identified as two of upper left anterior teeth, one of upper left intermediate tooth, two of lower left lateral teeth and one of lower right lateral tooth. 3) Judging from the size of these fossil teeth, the ancient great white sharks are estimated about 4.5 meter to 5.7 meter in total length based on the study of RANDALL (1973). 4) The origin and evolution of the great white shark will be clear by the following discoveries and the morphological and biostratigraphical studies on many fossil teeth from the Pliocene to Pleistocene strata in the Japanese Islands and other countries in future.
1984-11-25