長野県真田町本原の中部中新統伊勢山層から産出したヨロイザメの歯化石について
2005 年 59 巻 6 号 p. 383-388
詳細
2005 年 59 巻 6 号 p. 383-388
Three fossil shark teeth which are found from the lowest part of the Middle Miocene (15Ma) Iseyama Formation in Sanada-machi, Nagano Prefecture, central Japan, were described. These were identified as teeth of kitefin shark, Dalatias licha (Bonnaterre). This is the second record of Dalatias licha in Nagano Prefecture and also the first one from the Northern Fossa Magna region in Nagano Prefecture. The Iseyama Formation is mainly composed of mudstone which grades upward into interbeds, laminated mudstone, laminated sandy mudstone, interbeds and massive mudstone. Therefore, it is estimated by the habitat of Dalatias licha, the lithofacies and the mollusca fossils that the lowest part of the Iseyama Formation was deposited on the shelf slope deeper than 200 meters and the shelf edge.
