DIVISION II. RULES AND RECOMMENDATIONS
CHAPTER V. REJECTION OF NAMES
53.1. A name of a family, genus or species, unless conserved
(Art. 14) or sanctioned (Art.
15), is illegitimate if it is a later homonym, that is, if it is spelled exactly like a name based on a different type that was previously and validly published for a taxon of the same rank (see also
Art. 6 Note 2 and Art. 53.2
Ex. 1. The name Tapeinanthus Boiss. ex Benth. (1848), given to a genus of
Labiatae, is a later homonym of Tapeinanthus Herb. (1837), a name previously and validly published for a genus of
Amaryllidaceae. Tapeinanthus Boiss. ex Benth. is therefore unavailable for use. It was renamed
Thuspeinanta T. Durand (1888).
Ex. 2. The name Torreya Arn. (1838) is a nomen conservandum and is therefore available for use in spite of the existence of the earlier homonym
Torreya Raf. (1818).
Ex. 3. Astragalus rhizanthus Boiss. (1843) is a later homonym of the validly published name
A. rhizanthus Royle (1835) and is therefore unavailable for use. Boissier renamed it
A. cariensis Boiss. (1849).
A later homonym is unavailable for use even if the earlier homonym is illegitimate or is otherwise generally treated as a synonym.
Ex. 4. Zingiber truncatum
S. Q. Tong (1987) is illegitimate, being a later homonym of
Stokes (1812), even though the latter name is itself illegitimate under
because in its protologue the name
Christm. (1779) was cited in synonymy. It was renamed Z. neotruncatum
T. L. Wu & al. (2000).
The name Amblyanthera
Müll. Arg. (1860) is a later homonym of the validly published
Blume (1849) and is therefore unavailable for use, although
Blume is now considered to be a synonym of Osbeckia
53.2. A sanctioned name is illegitimate if it is a later homonym of another sanctioned name (see also
Art. 15 Note 1).
53.3. When two or more generic or specific names based on different types are so similar that they are likely to be confused (because they are applied to related taxa or for any other reason) they are to be treated as homonyms (see also
Art. 61.5). If established practice has been to treat two similar names as homonyms, this practice is to be continued if it is in the interests of nomenclatural stability.
* Ex. 6.
Names treated as homonyms: Asterostemma
Decne. (1838) and
Benth. (1880); Pleuropetalum
Hook. f. (1846) and Pleuripetalum
T. Durand (1888);
DC. (1828) and Eschweileria
Boerl. (1887); Skytanthus
Meyen (1834) and
* Ex. 7.
The three generic names Bradlea
Banks ex Gaertn. (1790), and Braddleya
Vell. (1827), all commemorating Richard Bradley, are treated as homonyms because only one can be used without serious risk of confusion.
* Ex. 8.
The names Acanthoica
Lohmann (1902) and
W. N. Ellis (1930), both designating flagellates, are sufficiently alike to be considered homonyms (Taxon 22: 313. 1973).
* Ex. 9.
Epithets so similar that they are likely to be confused if combined under the same generic or specific name:
and sinensis; ceylanica
and zeylanica; napaulensis, nepalensis,
and polyanthemus; macrostachys
and macrostachyus; heteropus
and poikilanthes; pteroides
and pteroideus; trinervis
and macrocarpum; trachycaulum
* Ex. 10.
Names not likely to be confused: Rubia
L. (1753) and
L. (1753); Monochaetum
(DC.) Naudin (1845) and Monochaete
Grev. (1863) and Peponium
Engl. (1897); Iris
L. (1753) and
(Pers.) Hedw. (1806); Desmostachys
Miers (1852) and Desmostachya
(Stapf) Stapf (1898);
Miers (1841) and Symphostemon
Hiern (1900); Gerrardina
Oliv. (1870) and
Engl. (1897); Urvillea
Kunth (1821) and Durvillaea
Bory (1826); Peltophorus
Desv. (1810; Gramineae
) and Peltophorum
(Vogel) Benth. (1840;
); Senecio napaeifolius
(DC.) Sch. Bip. (1845, 'napeaefolius';
Art. 60 Ex. 18
s MacOwan (1890; the epithets being derived, respectively, from
and Brassica napus
); Lysimachia hemsleyana
Oliv. (1891) and
Franch. (1895) (see, however, Rec.
); Euphorbia peplis
L. (1753) and
Names conserved against earlier names treated as homonyms (see
Gomont (vs Lyngbyea
Ruiz & Pav. (vs.
Lour.), both commemorating Columella, the Roman writer on agriculture;
Labill. (vs Cephalotos
The name Gilmania
Coville (1936) was published as a substitute name for
Coville (1893) because the author considered the latter to be a later homonym of Phyllogonium
Bridel (1827). Treating them as homonyms has become accepted, e.g. in Index Nominum Genericorum
, and the name Gilmania
has been accepted as legitimate ever since. Therefore the names Phyllogonum
are to continue
to be treated as homonyms.
53.4. The names of two subdivisions of the same genus, or of two infraspecific taxa within the same species, even if they are of different rank, are treated as homonyms, the later of which is illegitimate, if they have the same or a confusingly similar final epithet and are not based on the same type.
The names Andropogon sorghum
(L.) Hack. and A. sorghum
(L.) Hack. (in Candolle & Candolle, Monogr. Phan. 6: 502. 1889) are legitimate, since both have the same type; repetition of the final epithet is in accord with
Ex. 14. Anagallis arvensis
(L.) Gouan (Fl. Monsp.: 30. 1765), based on
L. (1759), makes illegitimate the name A. arvensis
Hartm. (Sv. Norsk Exc.-Fl.: 32. 1846), based on the later homonym
Ex. 15. Scenedesmus armatus
(Hortob.) Pankow (in Arch. Protistenk. 132: 153. 1986), based on
Hortob. (in Acta Bot. Acad. Sci. Hung. 26: 318. 1981), is a later homonym of
L. S. Péterfi (in Stud. Cercet. Biol. (Bucharest), Ser. Biol. Veg. 15: 25. 1963) even though the two names apply to taxa of different infraspecific rank.
(L. S. Péterfi) E. H. Hegew. (in Arch. Hydrobiol. Suppl. 60: 393. 1982), however, is not a later homonym since it is based on the same type as
L. S. Péterfi.
The same final epithet may be used in the names of subdivisions of different genera, and of infraspecific taxa within different species.
Ex. 16. Verbascum
Murb. (Monogr. Verbascum: 34, 593. 1933) is permissible, although there is an earlier
Murb. (Monogr. Celsia: 34, 56. 1926). This, however, is not an example to be followed, since it is contrary to
53.5. When it is doubtful whether names or their epithets are sufficiently alike to be confused, a request for a decision may be submitted to the General Committee (see
Div. III), which will refer it for examination to the committee(s) for the appropriate taxonomic group(s). A recommendation, whether or not to treat the names concerned as homonyms, may then be put forward to an International Botanical Congress, and, if ratified, will become a binding decision.
Names ruled as likely to be confused, and therefore to be treated as homonyms:
Kunth (1847) and F. gameleira
Standl. (1937) (Taxon 42: 111. 1993);
S. Moore (1895) and S. saltense
(Bitter) C. V. Morton (1944) (Taxon 42: 434. 1993);
Cambess. (1829; Caryophyllaceae
) and Ballardia
) (Taxon 42: 434. 1993).
Names ruled as not likely to be confused:
Ohwi (1931; extant Flacourtiaceae
) and Cathaya
Chun & Kuang (1962; fossil
) (Taxon 36: 429. 1987); Cristella
Pat. (1887; Fungi
H. Lév. (1915; Pteridophyta
) (Taxon 35: 551. 1986); Coluria
R. Br. (1823;
) and Colura
(Dumort.) Dumort. (1835; Hepaticae
) (Taxon 42: 433. 1993);
Hook. f. & Harv. (1845; Rhodophyta
) and Acanthococos
Barb. Rodr. (1900;
) (Taxon 42: 433. 1993); Rauia
Nees & Mart. (1823; Rutaceae
Traub (1957; Amaryllidaceae
) (Taxon 42: 433. 1993).
53.6. When two or more homonyms have equal priority, the first of them that is adopted in an effectively published text
(Art. 29, 30,
31) by an author who simultaneously rejects the other(s) is treated as having priority. Likewise, if an author in an effectively published text substitutes other names for all but one of these homonyms, the homonym for the taxon that is not renamed is treated as having priority.
Linnaeus simultaneously published "10."
(Sp. Pl.: 517. 1753) and "25." M. cinerea
(Sp. Pl.: 520. 1753). In 1759, he renamed species 10
L. and retained the name M. cinerea
for species 25, so that the latter is treated as having priority over its homonym.
Rouy & Foucaud (Fl. France 2: 30. 1895) published the name
with two different types, for two different taxa under different subspecies. Only one of these names can be maintained.
A homonym renamed or rejected under
remains legitimate and takes precedence over a later synonym of the same rank, should a transfer to another genus or species be effected.
Ex. 21. Mimosa cineraria
L. (1759), based on
L. (Sp. Pl.: 517 [non 520]. 1753; see Art. 53 Ex. 19), was transferred to
by Druce (1914) as P. cineraria
(L.) Druce. However, the correct name in
would have been a combination based on M. cinerea
had not that name been
successfully proposed for rejection.
2006, by International Association for Plant Taxonomy. This page last updated