<国立科博専報>山形県朝日村砂川産出の中期中新世板鰓類

概要

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Abundant shark teeth have been collected at Sunagawa, Asahimura, Yamagata Prefecture in the northeastern Japan. The majority of the shark teeth are found to belong to the genus Isurus of the family Lamnidae in the order Lamniformes. Among the teeth of Isurus, 4 species are found : I. benedeni, I. desori, I. hastalis, and I. planus. I. planus was most abundant among them. Most teeth from Sunagawa lack roots, and are difficult to determine their position on the jaws. As far as we are aware, there are almost no reports which described these four species of Isurus from a single locality. Beside species of Isurus, Carcharodon megalodon, Lamna sp. Odontaspis sp., and species of Carcharhinus have been collected from the locality. Considering the distribution of Recent species of the sharks, the paleoenvironment of Sunagawa at the time of the deposition was a warm open sea with sandy bottom.
国立科学博物館の論文
1984-12-01