Article 40. Synonymy of the type genus

40.1. Validity of family-group names not affected

When the name of a type genus of a nominal family-group taxon is considered to be a junior synonym of the name of another nominal genus, the family-group name is not to be replaced on that account alone.

^{Example. The name NEOSITTINAE Ridgeway, 1904 (Aves) is valid rather than DAPHOENOSITTINAE Rand, 1936, even though the name of the type genus Neositta Hellmayr, 1901 is a junior synonym of Daphoenositta De Vis, 1897.}

40.2. Names replaced before 1961

If, however, a family-group name was replaced before 1961 because of the synonymy of the type genus, the substitute name is to be maintained if it is in prevailing usage.

40.2.1. A name maintained by virtue of this Article retains its own author but takes the priority of the replaced name, of which it is deemed to be the senior synonym.

^{Recommendation 40A. Citation of author and date. If the author and date are cited, a family-group name maintained under the provisions of Article 40.2.1 should be cited with its original author and date (see Recommendation 22A.2.2), followed by the date of its priority as determined by this Article; the date of priority should be enclosed in parentheses.}

^{Example. The dipteran family name ORPHNEPHILIDAE Rondani, 1847, based on Orphnephila Haliday, 1832, was used until Bezzi (1913) synonymized Orphnephila with Thaumalea Ruthe, 1831 and adopted THAUMALEIDAE, based on the senior synonym Thaumalea. This family name has been almost universally used since that time and it is to be maintained. Had THAUMALEIDAE not come into prevailing usage, ORPHNEPHILIDAE would continue in use despite the fact that Orphnephila is a junior synonym. THAUMALEIDAE is cited with its own author and date, followed by the date of the replaced name in parentheses: THAUMALEIDAE Bezzi, 1913 (1847). It takes precedence over ORPHNEPHILIDAE Rondani, 1847, and any subsequently published synonyms.}