Article 67. General provisions
The name-bearing type of a nominal genus or subgenus is a nominal species called the "type species" [Art. 42.3].
67.1.1. A nominal genus and its nominotypical subgenus [Art. 44.1] have the same type species [Art. 61.2].
67.1.2. The name of a type species remains unchanged even when it is a junior synonym or homonym, or a suppressed name (see Article 81.2.1).
Recommendation 67A. Terminology. Only the term "type species" or a strictly equivalent term in another language should be used in referring to the name-bearing type of a nominal genus or subgenus. To avoid ambiguity the term "genotype," which has widespread use in a different sense in genetics, should not be used instead of "type species."
Recommendation 67B. Citation of type species. The name of a type species should be cited by its original binomen. If the name of the type species is, or is currently treated as, an invalid name, authors may also cite its valid synonym.
Example. Astacus marinus Fabricius, 1775, one of the nominal species originally included in the decapod crustacean genus Homarus Weber, 1795, was subsequently designated by Fowler (1912) as the type species of Homarus. The type species is, and should be cited as, Astacus marinus Fabricius, 1775. Astacus marinus Fabricius is currently synonymized with Cancer gammarus Linnaeus, 1758, but the latter is not the type species of Homarus and should not be cited as such. If mention of the type species is required it should be made in some such manner as "Type species Astacus marinus Fabricius, 1775, a junior synonym of Cancer gammarus Linnaeus, 1758"; or "Type species Astacus marinus Fabricius, 1775, now regarded as a synonym of Homarus gammarus (Linnaeus, 1758)".
A nominal species is only eligible to be fixed as the type species of a nominal genus or subgenus if it is an originally included nominal species.
67.2.1. In the meaning of the Code the "originally included nominal species" comprise only those included in the newly established nominal genus or subgenus, having been cited in the original publication by an available name (including citation by an incorrect spelling [Art. 67.6]) of a species or subspecies (see Articles 45.6 and 68.2), or having been cited there as the deliberate application of a previous misidentification (see Articles 11.10, 67.13 and 69.2.4).
67.2.2. If a nominal genus or subgenus was established before 1931 (in the case of an ichnotaxon, before 2000 [Art. 66.1]) without included nominal species [Art. 12], the nominal species that were first subsequently and expressly included in it are deemed to be the only originally included nominal species.
67.2.3. Mere reference in the original publication to a publication containing the name of a species does not by itself constitute an express reference of a nominal species to a nominal genus.
67.2.4. Mere citation of an available genus-group name as a synonym of another does not constitute inclusion of the nominal species of the latter in the former, or vice versa.
67.2.5. A nominal species is deemed not to be originally included if it was doubtfully or conditionally included, or was cited as a species inquirenda, or as a species incertae sedis.
Only the nomenclatural acts or other published statements of the author made when a nominal genus or subgenus is established are relevant in deciding
The type species of a nominal genus or subgenus is fixed originally if fixed in the original publication [Art. 68], or subsequently if fixed after the nominal genus or subgenus was established [Art. 69].
67.5.1. mention of a species as an example of a genus or subgenus;
67.5.2. mention of a particular character or structure as "type" or "typical" of a genus or subgenus; and
67.5.3. one made in an ambiguous or conditional manner.
Examples. A statement such as any of the following is not to be regarded as a type designation in the meaning of the Code: "Aus xus is a typical example of the genus Aus"; "the venation of the anterior wings of Aus xus is typical of the genus Aus"; "Aus xus may possibly be the type of Aus".
If the name of a type species, when fixed, is cited in the form of an incorrect spelling or an unjustified emendation, it is deemed to have been cited in its correct original spelling (see also Article 69.2.1).
If, in fixing the type species for a nominal genus or subgenus, an author wrongly attributes the name of the type species, or of the genus or subgenus, to an author or date other than that denoting its first establishment, or cites wrongly the first express inclusion of nominal species in that genus or subgenus, he or she is nevertheless to be considered, if the nominal species was otherwise eligible, to have validly fixed the type species. For previous misidentifications deliberately employed when fixing a type species, see Articles 11.10 and 67.13.
Example. Aus Dupont, 1790, established without a type species, is best known from the work of a later author, Smith (1810). If subsequently Bus xus is designated as the type species of "Aus Smith, 1810", that designation is to be accepted as a designation of the type species for Aus Dupont, 1790, providing Bus xus was eligible for designation as type species of the latter. Errors in attributing the authorship or date of Bus xus would also be immaterial.
If an author publishes a new genus-group name expressly as a new replacement name (nomen novum) for a previously established name, or replaces a previously established genus-group name by an unjustified emendation [Art. 33.2.3], both the prior nominal taxon and its replacement have the same type species, and type fixation for either applies also to the other, despite any statement to the contrary (see also Article 13.3).
67.8.1. The type species must be a nominal species eligible (see Article 67.2) for fixation as the type species of the prior nominal genus-group taxon.
Example. Bus Schmidt, 1890 was proposed expressly as a new replacement name (nomen novum) to replace a junior homonym, Aus Medina, 1880, non Dupont, 1860. If Cus xus is validly fixed as the type species of Aus Medina it is automatically the type species of Bus. If, on the other hand, no type species had been fixed for Aus Medina and Cus yus is validly fixed as the type species of Bus, it is also the type species of Aus Medina.
If a validly fixed type species is later found to have been misidentified, the provisions of Article 70.3 apply.
If two or more nominal genus-group taxa are included within a single taxonomic taxon at genus-group level, their respective type species remain unchanged (subject to Article 23, the valid name of the taxonomic taxon so formed is that of the nominal taxon with the oldest potentially valid name).
The fact that a nominal species is the type species of a nominal genus or subgenus does not prevent it from being the type species of another. In such a case, the genus-group names are objective synonyms of one another [Art. 61.3.3].
If a genus-group name was first published in an available work as a synonym of another name there used as valid, and was subsequently made available before 1961 under the provisions of Article 11.6.1, the type species of the nominal genus or subgenus first published as a synonym is that nominal species (cited by an available name) first directly associated with it.
67.12.1. If more than one nominal species was first directly associated with a genus-group name first published as a synonym and made available under Article 11.6.1, those nominal species are the originally included nominal species for the purposes of Articles 68 and 69.
Example. Meigen (1818) synonymized the manuscript generic names Palpomyia and Forcipomyia with Ceratopogon Meigen, 1803 (Diptera), by mentioning them under species of the latter. Both are available under the provisions of Article 11.6.1. Ceratopogon flavipes Meigen, the only species with which Palpomyia was associated, is automatically its type species by monotypy. Ceratopogon bipunctatus (Linnaeus) and C. albipennis Meigen, the only species with which Forcipomyia was associated, are the originally included species that are eligible for subsequent type fixation for Forcipomyia. The type species of Ceratopogon is not automatically the type species of either Palpomyia or Forcipomyia.
67.13.1. If an author fixes as the type species of a new nominal genus or subgenus a species originally included deliberately in the sense of a misidentification or misapplication by an earlier author of a name which had been previously established [Art. 67.2.1], the type species fixed by that action is deemed to be a new nominal species [Arts. 11.10, 50.1.2 and 70.4; for the name-bearing type of this species see Article 72.4.2].
67.13.2. For the subsequent designation as the type species of a previously established genus-group taxon of a species originally included as an expressly stated misidentification, see Article 69.2.4.
67.14. Type species disregarded in collective groups. If the name of a nominal genus-group taxon is subsequently applied to a collective group, the type species of that taxon is disregarded while the name is used as a collective-group name (see also Article 23.7).
Example. Cercaria O.F. Müller, 1773, established for a genus of digenean helminths and treated as the name of a nominal genus by many 19th century authors as if C. lemna Müller, 1773 was its type species, is now used as a collective-group name for trematode larvae that cannot be placed with certainty in known genera; Cercaria is used in this way irrespective of any taxonomic treatment of it in synonymy.