2020 Volume 78 Issue 3-4 Pages 87-104
A subumbonal pit was found in the hinge of the venerid genus Ezocallista Kuroda in Kamada, 1962, for the first time. This finding supports the hypothesis that Ezocallista is more closely related to Saxidomus Conrad, 1837 than to Callista Poli, 1791. Only one Recent species, Saxidomus purpurata (Sowerby, 1852) is known from the western side of the Pacific. This species lives in temperate to cold water around Japan, Korea and in cold water in Bohai Sea in China and the Pojet, Amur and Peter the Great Bays in Russia. The oldest reliable records of this species in cool-temperate water have been recovered from the uppermost Miocene to the lowermost Pliocene Tatsunokuchi Formation in Miyagi Prefecture, northeastern Japan. That occurrence suggests that Saxidomus first adapted to a cold-water environment in its northernmost habitat during the latest Miocene to early Pliocene.