Undetermined undetermined

Hsu, Chia-Hsin, Osipova, Diana & Lin, Chien-Hsiang, 2025, Fossil freshwater mollusks from the Early Pleistocene (Calabrian) of northern Taiwan, Geodiversitas 47 (20), pp. 721-737 : 729-730

Unionidae gen. et sp. indet.

( Fig. 7B)

MATERIAL EXAMINED. — Taiwan • 1 specimen; Shuiniukeng (= Water Buffalo Valley ), New Taipei City; Tananwan Formation, Early Pleistocene, Calabrian ; ASIZF0100922 .

DESCRIPTION

Flat fragment of the inner side of the valve with nacreous layer. The fragment represents ventral part of the shell. 2 cm in length and width. Shell surface appears smooth, no obvious sculpture.

REMARKS

Based on previous reports of freshwater bivalves in Taiwan ( Chang 1991; Chung & Shao 2022), only one family, Unionidae Rafinesque, 1820 , with nacreous shells are documented in this region. Representatives of Unionidae tend to have elongated shells of a bigger size with convex ventral margin. Although our specimen is fragmentary, the preserved mold on the bedrock reveals ventral part of the shell that highly resemble unionids. Better-preserved specimens from the study area are required for further identification.