1. Fossil Clausiliidae from Europe are known since the Upper Cretaceous and traced through the Tertiary and Quaternary.
2. In contrast to several other fossil stylommatophoran groups, relationships of fossil Clausiliidae to other ones and to extant groups can be recognized with high probability, because they are highly diverse and rich in characters, especially of their closing apparatus.
3. Rich representative faunas of fossil Clausiliidae allow conclusions to climate and vegetation; changes of clausiliid faunas are the result of climatic changes.
4. As a rule, because of their high evolutionary rate, fossil Clausiliidae have a small stratigraphic range. Therefore, in comparison with other stylommatophoran groups, they have a high biostratigraphic value.
5. Fossil Clausiliidae give keys for the reconstruction of the evolution of the family, because relationships to extant species can be recognized (see 2.) and appearance dates (first and last ones) can be stated.
Nevertheless, there are several extinct clausiliid groups the relationships of which are unclear, especially if the material is scarce and essential characters cannot be examined.