Article 29. Family-group names
The suffix -OIDEA is used for a superfamily name, -IDAE for a family name, -INAE for a subfamily name, -INI for the name of a tribe, and -INA for the name of a subtribe. These suffixes must not be used at other family-group ranks. The suffixes of names for taxa at other ranks in the family-group are not regulated.
29.2.1. Names in the genus and species groups which have endings identical with those of the suffixes of family-group names are not affected by this Article.
Examples. The names of the following taxa at ranks below the family group are not affected by their having endings identical to those of suffixes of family-group names: the genus Ranoidea (Amphibia) and the species Collocalia terraereginae (Aves), Concinnia martini (Reptilia) and Hyla mystacina (Amphibia).
The stem of a family-group name is based on the name of its type genus [Art. 63] and determined as follows.
29.3.1. If a generic name is or ends in a Greek or Latin word, or ends in a Greek or Latin suffix, the stem for the purposes of the Code is found by deleting the case ending of the appropriate genitive singular.
Examples. Coccinella (genitive Coccinellae, stem Coccinell-) gives the family name COCCINELLIDAE. Similarly Culex (genitive Culicis, stem Culic-) gives CULICIDAE, Reduvius (genitive Reduvii, stem Reduvi-) gives REDUVIIDAE, Archaeopteryx (genitive Archaeo-pterygis, stem Archaeopteryg-) gives ARCHAEOPTERYGIDAE.
22.214.171.124. If the stem so formed ends in -id, those letters may be elided before adding the family-group suffixes. If, however, the unelided form is in prevailing usage, that spelling is to be maintained, whether or not it is the original spelling.
Example. The family-group names HALIOTIDAE and HALIOTOIDEA are not changed to HALIOTIDIDAE and HALIOTIDOIDEA, even though the stem of Haliotis is Haliotid-, as the latter spellings are not in prevailing usage.
29.3.2. If the name of a genus is or ends in a Greek word latinized with a change in ending, the stem is that appropriate to the latinized form, as determined in Article 29.3.1.
Example. In the generic name Leptocerus, of which the second part is latinized from the Greek word keras, the stem for the formation of the family-group name is Leptocer-, not Leptocerat-, as it would be if it were not latinized.
29.3.3. If a generic name is or ends in a word not Greek or Latin, or is an arbitrary combination of letters, the stem for the purposes of the Code is that adopted by the author who establishes the new family-group taxon, either the entire generic name (see Article 29.6), or the entire generic name with the ending elided, or the entire generic name with one or more appropriate linking letters incorporated in order to form a more euphonious family-group name.
If after 1999 a new family-group name is based on a generic name which is or ends in a Greek or Latin word or ends in a Greek or Latin suffix, but its derivation does not follow the grammatical procedures of Articles 29.3.1 or 29.3.2, its original spelling must be maintained as the correct original spelling, provided
29.4.1. it has a correctly formed suffix [Art. 29.2], and
29.4.2. its stem is formed from the name of the type genus as though it were an arbitrary combination of letters [Art. 29.3.3].
Example. If an author proposes after 1999 the name PROREXIDAE based on the generic name Prorex (genitive: Proregis) that spelling is to be maintained, even though the spelling PROREGIDAE would have been proper under Article 29.3.1.
If a spelling of a family-group name was not formed in accordance with Article 29.3 but is in prevailing usage, that spelling is to be maintained, whether or not it is the original spelling and whether or not its derivation from the name of the type genus is in accordance with the grammatical procedures in Articles 29.3.1 and 29.3.2.
An author wishing to establish a new family-group name must avoid its homonymy with any known previously established names by forming an appropriate stem from the name of the type genus. (See Article 55.3.1 for the elimination of homonymy between existing family-group names).
Recommendation 29A. Use of entire generic name as the stem as the preferred means of avoiding homonymy between family-group names. As a means of avoiding homonymy between a new family-group name and a previously established one, due to the respective type genera having identical stems (as determined by Article 29.3), an author is advised to use the entire name of the type genus of the new family-group taxon as the stem.
Example. An author proposing a new family name based on a type genus Mirum can avoid its homonymy with MIRIDAE Hahn, 1833 (Heteroptera, type genus Miris Fabricius, 1794) by taking the stem to be Mirum-, and hence forming the name MIRUMIDAE. (The Commission followed an analogous course in Opinion 898 (1970) when ruling that the stem of Mira Schellenberg, 1803 (Hymenoptera) is Mira-, thereby emending the spelling of the family-group name MIRINI Ashmead, 1900 to MIRAINI and so removing homonymy with MIRIDAE Hahn).