Homonym (biology)

{{short description|Scientific name that is identical in spelling to a name with a different type}} {{use dmy dates|date=September 2023}} In '''biology''', a '''homonym''' is a name for a taxon that is identical in spelling to another such name, that belongs to a different taxon.

The principle in the International Code of Zoological Nomenclature, coordinate with the principle of priority, is that the first such name to be published is the '''senior homonym''' and is to be used (it is "valid"); any others are '''junior homonyms''' and must be replaced with new names.

:For example: :*Cuvier proposed the genus ''Echidna'' in 1797 for the spiny anteater. :*However, Forster had already published the name ''Echidna'' in 1777 for a genus of moray eels. :*Forster's use thus has priority, with Cuvier's being a junior homonym. :*Illiger published the replacement name ''Tachyglossus'' in 1811.

It is, however, possible that if a senior homonym is archaic, and not in "prevailing usage," it may be declared a ''nomen oblitum'' and rendered unavailable, while the junior homonym is preserved as a ''nomen protectum''.

:For example: :*Agassiz proposed the name ''Bucardium'' in 1848 as an emendation of the genus name ''Buccardium'' Megerle, 1811 (now considered a synonym of ''Glossus''). :*Later, Gray used the name ''Bucardium'' in 1853 for a genus of cockles. :*Even though Agassiz' name has priority, it was not used as a valid name after 1899, while Gray's name was widely accepted (and is still in use). :*Under ICZN Article 23.9, the junior homonym is protected from being replaced, and the senior homonym is considered unavailable.<ref>{{Cite web |url=https://code.iczn.org/validity-of-names-and-nomenclatural-acts/article-23-principle-of-priority/#art-23-9 |title=Article 23.9. Reversal of precedence. |website=The Code Online {{!}} International Commission on Zoological Nomenclature |access-date=2025-09-30}}</ref>

Similarly, the International Code of Nomenclature for algae, fungi, and plants (ICN) specifies that the first published of two or more homonyms is to be used: a '''later homonym''' is "illegitimate" and is not to be used unless conserved (or sanctioned, in the case of fungi).<ref name=ICBN-53>{{cite web|title=International Code of Nomenclature for algae, fungi, and plants, Articles 53, 15, and 13|url=http://www.iapt-taxon.org/nomen/main.php|access-date=14 June 2013}}</ref>

:Example: the later homonym ''Myroxylon'' L.f. (1782), in the family Leguminosae, is conserved against the earlier homonym ''Myroxylon'' J.R.Forst. & G.Forst. (1775) (now called ''Xylosma'', in the family Salicaceae).

==Limits and exceptions== Under the zoological code, homonymy can only occur '''within''' each of the three nomenclatural ranks (family-rank, genus-rank, and species-rank) but not '''between''' them; there are thousands of cases where a species epithet is identical to a genus name but not a homonym (sometimes even occurring in the genus it is identical to, such as ''Gorilla gorilla'', termed a "tautonym"), and there are some rare cases where a family-rank name and a genus-rank name are identical (e.g., the superfamily name Ranoidea and the genus name ''Ranoidea'' are not homonyms). Unavailable names do not compete for homonymy.<ref>{{Cite web |url=https://code.iczn.org/homonymy/article-54-names-that-do-not-enter-into-homonymy/ |title=Article 54. Names that do not enter into homonymy. |website=The Code Online {{!}} International Commission on Zoological Nomenclature |access-date=2025-09-30}}</ref> The botanical code is generally similar, but prohibits tautonyms.

===Parahomonyms=== Under the botanical code, names that are similar enough that they are likely to be confused are also considered to be homonymous (article 53.3). For example, ''Astrostemma'' Benth. (1880) is an illegitimate homonym of ''Asterostemma'' Decne. (1838). The zoological code considers even a single letter difference to be sufficient to render family-rank and genus-rank names distinct (Article 56.2), though for species names, the ICZN specifies a number of spelling variations (Article 58) that are considered to be identical.<ref>{{Cite web |url=https://code.iczn.org/homonymy/article-58-variant-spellings-of-species-group-names-deemed-to-be-identical/ |title=Article 58. Variant spellings of species-group names deemed to be identical. |website=The Code Online {{!}} International Commission on Zoological Nomenclature |access-date=2025-09-30}}</ref>

===Hemihomonyms=== Both codes only consider taxa that are in their respective scope (animals for the ICZN; primarily plants for the ICN). Therefore, if an animal taxon has the same name as a plant taxon, both names are valid. Such names are called ''hemihomonyms''.<ref>{{cite journal|last1=Shipunov|first1=Alexey|title=The problem of hemihomonyms and the on-line hemihomonyms database (HHDB)|journal=Bionomina|date=2011|volume=4|issue=1|pages=65–72|doi=10.11646/bionomina.4.1.3|doi-access=free}}</ref>

For example, the name ''Erica'' has been given to both a genus of spiders, ''Erica'' Peckham & Peckham, 1892, and to a genus of heaths, ''Erica'' L.

Another example is ''Cyanea'', applied to the lion's mane jellyfish ''Cyanea'' Péron and Lesueur and to the Hawaiian lobelioid ''Cyanea'' Gaudich.

Hemihomonyms are possible at the species level as well, with organisms in different kingdoms sharing the same binomial nomenclature. For instance, ''Orestias elegans'' denotes both a species of fish (kingdom Animalia) and a species of orchid (kingdom Plantae). Such duplication of binomials occurs in at least nine instances.

{| class="wikitable" ! Animal ! Plant |- | ''Adesmia muricata'' (Linnaeus, 1758) (a beetle) | ''Adesmia muricata'' (Jacq.) DC. (a legume) |- | ''Agathis montana'' Shestakov, 1932 (a wasp) | ''Agathis montana'' de Laub. (the Mount Panié kauri, a conifer) |- | ''Baileya australis'' (Grote, 1881) (the small baileya moth) | ''Baileya australis'' Rydb. syn. ''B. multiradiata'' (a desert marigold) |- | ''Centropogon australis'' (White, 1790) (the fortescue, a waspfish) | ''Centropogon australis'' Gleason (a bellflower) |- | ''Cuspidaria cuspidata'' (Olivi, 1792) (a bivalve) | ''Cuspidaria cuspidata'' (M. Bieb.) Takht. syn. ''Erysimum cuspidatum'' (a wallflower) |- | ''Ficus variegata'' Röding, 1798 (the true fig shell, a sea snail) | ''Ficus variegata'' Blume (the common red-stem fig) |- | ''Gaussia princeps'' (T. Scott, 1894) (a copepod) | ''Gaussia princeps'' H.Wendl. (a palm) |- | ''Orestias elegans'' Garman, 1895 (a pupfish) | ''Orestias elegans'' Ridl. (an orchid) |- | ''Tritonia pallida'' Stimpson, 1855 (a nudibranch) | ''Tritonia pallida'' Ker Gawl. (an iris) |}

==See also== * {{annotated link|Glossary of scientific naming}} * {{annotated link|Isonym}}. Isonyms have no nomenclatural status (they are not validly published). * {{annotated link|Priority (biology)}}

==References== {{reflist|33em}}

==External links== {{Wikispecies-inline|List of valid homonyms}}

Category:Botanical nomenclature Category:Zoological nomenclature 01 Category:Taxonomy (biology)