†Theodoxus pisiformis

Theodoxus pisiformis is an extinct freshwater snail from the early Paleogene of Western Europe, notable for its small, globular shell—reflected in its name, pisiformis, meaning “pea-shaped.” The shell typically measures around 5–9 mm, making it smaller than many of its relatives. Unlike other Theodoxus species with flatter or more conical forms and bold patterns, T. pisiformis is distinguished by its rounded profile and fine, zigzagging stripes. Its inner shell lip is unusually smooth, lacking the prominent teeth common in the genus. Fossils place it in ancient rivers and lagoons, where it likely grazed algae on hard surfaces, much like its modern kin.