First record of Late Pleistocene holoplanktonic mollusks (Gastropoda, Euthecosomata, Pterotracheoidea) from northern Taiwan

Pelagic gastropods, including pteropods and heteropods, are cosmopolitan organisms recorded in Cenozoic deposits across the globe.Their fossils serve as valuable tools for paleoenvironmental reconstruction and enable precise stratigraphic correlations.Numerous Neogene and Quaternary assemblages of pelagic gastropods have been documented in the Indo-West Pacific region, spanning from Indonesia to central Japan.In Taiwan, molluscan fossil assemblages are abundant and diverse, predominantly comprising gastropods and bivalves.However, pteropod records from Taiwan are limited, with only two species previously reported from the Oligocene.This study investigates a previously undocumented Late Pleistocene assemblage of holoplanktonic pelagic gastropods from the Toukoshan Formation in northern Taiwan.The pteropod fauna includes nine taxa from the families Creseidae and Cavoliniidae, and one species of the heteropod family Atlantidae.Notably, the Toukoshan species Diacria cf.philippinensis and Diacavolinia cf.bandaensis represent the first Pleistocene records.Additionally, the heteropod Atlanta turriculata marks the first occurrence of this group in Taiwan.All identified species are epipelagic, corroborating earlier depth estimates for the fossil-bearing strata.The Toukoshan holoplanktonic assemblage shares similarities with other Pleistocene faunas from Okinawa and Honshu in Japan, highlighting regional paleoceanographic connections during this period.