Soft-sediment adaptations in a new Silurian gastropod from Central Asia

Specimens of the gastropod Isfarispira septata gen. et sp. nov., from the Silurian of Central Asia, are characterized by a large, lenticular, multi-whorled shell with a flattened base, a low rate of expansion of the broad whorls, internal septa at intermediate growth stages and a prominent circumbilical flange which closed off much of the umbilicus. These morphological features reflect adaptation to life on a soft substratum, collectively serving to inhibit sinking into the soft sediment by increasing the area of the basal surface. I. septata is interpreted as a sedentary, or only infrequently mobile gastropod.