To all,

Thank you for the help in the identification of Planorbella duryi.

My taxonomic question deals with how do they determine rankings for any group
of similar organisms?  For instance, is the degree of similarity and
differences within the family Donacidae, the same as within the family
Turridae?  Or going outside of the mollusca, the insect family Carabidae, or
even the plant family Cucurbitacea?  Is it possible that a range of
differences that might warrent generic or subfamily ranking in one phylum
could be given family or superfamily ranking elsewhere?

Thank you,
Martin