It is known that many endemic mammals lived in the islands of the world during Pleistocene to the present. In this paper, the distribution of faunas and their transition in the islands of the world are examined. As a result, it became clear that many of mammals of the islands were converted after the late Middle Pleistocene and became unique. Because animal migration occurs in their habitat environment, it is thought that these animals migrated through the land bridge that was formed in the late Middle Pleistocene, and then an endemic fauna was formed after that was isolated to the island by the sea level rise of 1,000 m.

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 The Nakaminato Group (Upper Cretaceous, Campanian-Maastrichtian), which is exposed along the Pacific coast in Hitachinaka, Ibaraki Prefecture, central Japan, yields a variety of animal fossils such as ammonoids, bivalves, reptiles, etc. Here we report seven newly collected fossil shark teeth, including Carcharias cf. gracilis, cf. Carcharias sp., and cf. Squalicorax sp. In Japan, the Campanian-Maastrichtian shark teeth have been known from the Yezo, Nemuro, and Izumi Groups. However, Carcharias was not reported from the Campanian-Maastrichtian deposit in Japan. Squalicorax was known from the Izumi Group in southwestern Japan. On the other hand, this genus has not been reported from the Yezo and Nemuro Groups in Hokkaido of northern Japan. The new specimens from the Nakaminato Group suggest that these large predatory sharks, Carcharias and Squalicorax, might have co-existed in the western North Pacific Ocean during the Campanian-Maastrichtian.

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 2016年６月から2017年６月にかけて岐阜県瑞浪市土岐町において瑞浪北中学校を建設するための敷地造成工事が実施された．この工事現場は，瑞浪市指定天然記念物「瑞浪化石産地」（昭和36（1961）年６月９日指定）の指定区域内であったため，事前に工事の際に化石が産出した場合は瑞浪市化石博物館に連絡する取り決めがなされた．そして，現場内に露出した下部中新統瑞浪層群明世層戸狩部層上部～明世層山野内部層中部の地層からCrenomytilus grayanus（エゾイガイ）をはじめとする貝類，フジツボ類，魚類，鯨類など多くの化石が産出した．  瑞浪市では，地層や化石が文化財（天然記念物）として長年にわたって保護されており，行政の組織内に化石調査に対する理解が広がっていたことにより，工事業者の協力や市役所関係部署の補助も得て調査が実施された．今回発見されたエゾイガイなどの研究成果は，瑞浪市化石博物館研究報告第44号−特別号−にまとめられ，産出化石の一部を活用して瑞浪市化石博物館常設展の改装と学校教育への導入が実施された．

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