Completed description of Bhutanese Tibetoradix cf. hookeri (Gastropoda, Pulmonata, Lymnaeoidea), with species-specific, environmentally induced decollation

In two samples of Tibetoradix cf. hookeri, collected at different altitudes, the shells differ by being decollated at the highest locality and not so at the lowest. Potential decollation is hypothesized to be an adaptive character state enabling a longer lifespan at higher altitudes in the Himalaya.