Article: Sinistral hyperstrophic coiling in a Devonian gastropod from Bohemia with an in situ operculum

A paucispiral operculum is described in situ in a specimen of Tychobrahea aerumnans from the Devonian of Bohemia. The small turbiniform gastropod shell appears to be dextrally orthostrophically coiled in similar fashion to most other fossil and extant gastropod shells, but the clockwise-coiling of the exterior surface of the operculum indicates that coiling of the shell is sinistral hyperstrophic. This is the first description of an operculate gastropod with this type of coiling in the fossil record.