Calyptraeidae are limpets with irregularly shaped shells with a small internal cup or shelf; many species show sex reversal, becoming males early in life, then changing into females during old age. Most members of the prosobranch family Calyptraeidae begin life as fully functional males but, after a transitional phase, spend their remaining life span as females.

Crepidula species, for example, form stacks of as many as 19 individuals. The younger ones on top are male, the old ones on the bottom female, and those in the middle are intermediate in sex.