Discovery of Geloina (Bivalvia: Corbiculidae) from the Miocene Kadonosawa Formation in the Ninohe area, Iwate Prefecture, northeastern Japan, and its paleobiogeographic significance

Abstract

Fossil Geloina, a tropical bivalve, was found from the uppermost Lower Miocene Tate Sandstone Member of the Kadonosawa Formation in Iwate Prefecture, northeastern Honshû, Japan. This is the northernmost Neogene and Quaternary record of the genus in the northwestern Pacific. The specimen is identified as Geloina cf. stachi Oyama. The occurrence indicates that the mangrove swamp has extended its distribution as northward as the northern part of Honshû in the Mid-Neogene Climatic Optimum age (ca. 16.5-15.0 Ma).