古第三紀翼足類（腹足綱, 有殻翼足目）の日本で初めての産出

概要

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More than 100 pteropod specimens were collected from each of the Eocene Shikiyama and Oniike formations in the Amakusa area, Kumamoto Prefecture, Southwest Japan. These fossils constitute the first Paleogene pteropod record from Japan. The pteropods from the Shikiyama Formation consist of five species, including Limacina canadaensis Hodgkinson, L. pygmaea (Lamarck), and Praehyalocylis annulata (Tate). The pteropods from the Oniike Formation consist of six species, including Limacina canadaensis, L. lotschi (Tembrock), Creseis hastata (Meyer), C. simplex (Meyer), and Praehyalocylis annulata. Both of these pteropod faunas are characterized by the predominance of Limacina in species diversity and specimen abundance. The faunas are similar to the pteropod faunas from the Middle to Upper Eocene of Europe and the east coast of North America in terms of generic composition and the predominance of Limacina.