Some 1,048 names at the rank of subtribe, tribe, subfamily, family and superfamily have been proposed for Recent and fossil bivalves. All names are listed in a nomenclator giving full bibliographical reference, date of publication, type genus, and their nomenclatural availability and validity under the International Code of Zoological Nomenclature. Another 274 names, established for categories above the family-group are listed separately. A working classification attempts to group all bivalve family-group names into a single system based on current hypotheses of relations and synonymies. At several rank levels, the groups are given in alphabetical rather than some assumed phylogenetic arrangement, reflecting current uncertainties and conflicting results from anatomical, molecular, and fossil data.
Altogether, the classification recognizes as valid a total of 324 families, of which 214 are known exclusively as fossils and 110 occur in the Recent with or without a fossil record.