長野県北部の柵累層(新第三系)から産出したネズミザメ類の歯化石について

抄録

Six fossil teeth of lamnoid sharks found from the Shigarami Formation (Neogene) in the north part of Nagano Prefecture, Central Japan are described. Five of them occurred from the Ogikubo Sandstone and Mudstone Member, Middle Pliocene (4-3 Ma), are lower left and upper left lateral teeth of the great white shark, Carcharodon carcharias (Linnaeus). One of them occurred from the Gonda Conglomerate and Sandstone Member, Late Miocene-Early Pliocene ( 6-5 Ma), is an upper left anterior tooth of Isurus escheri (Agassiz). This paper is the first report of Carcharodon carcharias from Nagano Prefecture and also the first description of Isurus escheri from Japan.