上部鮮新統掛川層群大日砂層からダイミョウイモガイの化石産出とその意義

概要

論文の詳細を見る
A specimen of Cleobula was found in a shell-concentrated bed intercalated in the Upper Pliocene Dainichi Sand of the Kakegawa Group at Asuka, Kakegawa City, Shizuoka Prefecture. The shell bed yields dominantly warm sea-water molluscan fossils such as Venericardia panda, Glycymeris albolineata, Turritella perterebra and Babylonia elata, associated with many other species now living in the upper sublittoral zone of central and western Japan. Specific identification of Cleobula is usually difficult only based on shell forms. Cleobula shells, however, exhibit distinct color patterns characteristic of each species. Under ultraviolet light of 352nm wave length the fossil specimen was ornamented with color patterns of spiral rows of dots or dashes on the body whorl. On the basis of the color pattern, the fossil specimen is identified with Cleobula betulina (Linnaeus). This is the first record of Cleobula betulina from the Pliocene in Japan. Cleobula betulina is a tropical species living in the Indo-West Pacific. The northernmost limit of its present distribution is off Shikoku. Therefore the occurrence of Cleobula betulina suggests that the upper sublittoral fauna in the Kakegawa area in the Late Pliocene was influenced by warmer sea-water current than the present Kuroshio Current.
日本貝類学会の論文
1995-03-31