There are several gastropod families and genera in which it is possible to determine a complete, fully mature adult specimen
by the formation of a structure that puts an end to the length growth (usually a thickened outer lip and a callused shield
along the columella. Such groups with determined growth may also produce exceptionally small adult shells, which may be
submitted for recording the "smallest adult specimen of a species". Spines and canals of such applicants must not be broken,
the shells have to be fully intact.
Groups that apply for this category include:
- Cypraeidae, Strombidae, Triviidae, the genus Morum (Harpidae),
- and with few exceptions, species of Cassidae and Ovulidae.
There are other families and genera with members that have determined growth, but listing their minimum world records make
little sense as the species do not show much variation in size (Marginellidae, Cerithiidae, Columbellidae, Nassariidae). The
same method of measurement and the 0.3 mm margin rules apply, and only specimens over 5.0 millimeters will be considered for
the time being.