Fig. 1

Photographs of the Terebratalia coreanica and Laqueus rubellus shells examined in this study. The modern T. coreanica shells were collected from Otsuchi Bay, northeastern Japan, and L. rubellus shells were collected from Sagami Bay, central Japan. The fossil shells are from the Pliocene Tentokuji Formation in Minehama, northeastern Japan. a Modern T. coreanica. b–f Fossil T. coreanica. g Modern L. rubellus. h–l Fossil L. rubellus. Only the ventral valves were examined in this study