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.
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