Article 51. Citation of names of authors.
51.1. Optional use of names of authors. The name of the author does not form part of the name of a taxon and its citation is optional, although customary and often advisable.
Recommendation 51A. Citation of author and date. The original author and date of a name should be cited at least once in each work dealing with the taxon denoted by that name. This is especially important in distinguishing between homonyms and in identifying species-group names which are not in their original combinations. If the surname and forename(s) of an author are liable to be confused, these should be distinguished as in scientific bibliographies.
Recommendation 51B. Transliteration of author's name. When the author's name is customarily written in a language that does not use the Latin alphabet it should be given in Latin letters with or without diacritic marks.
51.2. Form of citation of authorship. The name of an author follows the name of the taxon without any intervening mark of punctuation, except in changed combinations as provided in Article 51.3.
Recommendation 51C. Citation of multiple authors. When three or more joint authors have been responsible for a name, then the citation of the name of the authors may be expressed by use of the term "et al." following the name of the first author, provided that all authors of the name are cited in full elsewhere in the same work, either in the text or in a bibliographic reference.
51.2.1. The name of a subsequent user, if cited, is to be separated from the name of the taxon in some distinctive and explicit manner, but not by parentheses (cf. Article 51.3), unless an explanation is included.
Example. Reference to Cancer pagurus Linnaeus as used by Latreille may be cited as "Cancer pagurus Linnaeus sensu Latreille", or as "Cancer pagurus Linnaeus (as interpreted by Latreille)" or in some other distinctive manner, but not as "Cancer pagurus Latreille" or "Cancer pagurus (Latreille)".
Recommendation 51D. Author anonymous, or anonymous but known or inferred.v If the name of a taxon was (or is deemed to have been) established anonymously, the term "Anon." may be used as though it was the name of the authors. However, if the authorship is known or inferred from external evidence, the name of the author, if cited, should be enclosed in square brackets to show the original anonymity. For availability of names proposed anonymously see Article 14.
Recommendation 51E. Citation of contributors. If a scientific name and the conditions other than publication that make it available [Arts. 10 to 20] are the responsibility not of the author of the work containing them, but of some other person(s), or of less than all of joint authors, the authorship of the name, if cited, should be stated as "B in A", or "B in A & B", or in whatever form is appropriate to facilitate information retrieval (normally the date should also be cited).
Recommendation 51F. Citation of author of unavailable or excluded names. If citation of authorship for an unavailable or excluded name [Rec. 50C] is necessary or desirable, the nomenclatural status of the name should be made evident.
Examples. Halmaturus rutilis Lichtenstein, 1818 (nomen nudum); Yerboa gigantea Zimmermann, 1777 (published in a work rejected by the Commission in Opinion 257); "Pseudosquille" (a vernacular name published by Eydoux & Souleyet (1842)).
51.3. Use of parentheses around authors' names (and dates) in changed combinations. When a species-group name is combined with a generic name other than the original one, the name of the author of the species-group name, if cited, is to be enclosed in parentheses (the date, if cited, is to be enclosed within the same parentheses).
Example. Taenia diminuta Rudolphi, when transferred to the genus Hymenolepis, is cited as Hymenolepis diminuta (Rudolphi) or Hymenolepis diminuta (Rudolphi, 1819).
51.3.1. Parentheses are not used when the species-group name was originally combined with an incorrect spelling or an emendation of the generic name (this applies even though an unjustified emendation is an available name with its own authorship and date [Art. 33.2.3]).
Example. The species-group name subantiqua d'Orbigny, 1850 was established in combination with Fenestrella, d'Orbigny's incorrect spelling of Fenestella Lonsdale, 1839. The species is cited as Fenestella subantiqua d'Orbigny, 1850, and not as Fenestella subantiqua (d'Orbigny, 1850).
51.3.2. The use of parentheses enclosing the name of the author and the date is not affected by the presence of a subgeneric name, by transfer to a different subgenus within the same genus, by a change of rank within the species group, or by transfer of a subspecies to a different species within the same genus.
Example. Goniocidaris florigena Agassiz, when transferred to the genus Petalocidaris, is cited as Petalocidaris florigena (Agassiz). When Petalocidaris is treated as a subgenus of Goniocidaris the parentheses are omitted, even when the complete citation is given as Goniocidaris (Petalocidaris) florigena Agassiz.
51.3.3. If before 1961 a new species-group name was established in combination with a previously available genus-group name and, at the same time, the author conditionally proposed a new nominal genus for it, parentheses are not used with the author's name when the species-group name is used in combination with the previously established generic name, but are used when the species-group name is combined with the conditionally proposed generic name (see Article 18.104.22.168).
Example. Lowe (1843) established the new fish species Seriola gracilis and at the same time conditionally proposed a new genus Cubiceps to contain that nominal species. When included in Cubiceps, the name is cited as Cubiceps gracilis (Lowe, 1843).
Recommendation 51G. Citation of person making new combination. If it is desired to cite both the author of a species-group nominal taxon and the person who first transferred it to another genus, the name of the person forming the new combination should follow the parentheses that enclose the name of the author of the species-group name (and the date, if cited; see Recommendation 22A.3).
Examples. Limnatis nilotica (Savigny) Moquin-Tandon; Methiolopsis geniculata (Stål, 1878) Rehn, 1957.