[:Chapter13:Chapter 13: The Type Concept in Nomenclature]
Article 61. Principle of Typification.
61.1. Statement of the Principle of Typification. Each nominal taxon in the family, genus or species groups has actually or potentially a name-bearing type. The fixation of the name-bearing type of a nominal taxon provides the objective standard of reference for the application of the name it bears.
61.1.1. No matter how the boundaries of a taxonomic taxon may vary in the opinion of zoologists the valid name of such a taxon is determined [Art. 23.3] from the name-bearing type(s) considered to belong within those boundaries.
61.1.2. Objectivity provided by typification is continuous through the hierarchy of names. It extends in ascending order from the species group to the family group. Thus the name-bearing type of a nominal species-group taxon is a specimen or a set of specimens (a holotype, lectotype, neotype or syntypes [Art. 72.1.2]), that of a nominal genus-group taxon is a nominal species defined objectively by its type; that of a nominal family-group taxon is the nominal genus on which its name is based.
61.1.3. Once fixed, name-bearing types are stable and provide objective continuity in the application of names. Thus the name-bearing type of any nominal taxon, once fixed in conformity with the provisions of the Code, is not subject to change except in the case of nominal genus-group taxa as provided in Article 70.3.2, of nominal species-group taxa as provided in Articles 74 and 75, and by use of the plenary power of the Commission [Art. 81].
61.2. Name-bearing types of nominotypical taxa. The name-bearing type of a nominal taxon is also the name-bearing type of its nominotypical taxon [Arts. 37.1, 44.1, 47.1], and the fixation of a name-bearing type for one constitutes fixation for the other also.
61.2.1. If different name-bearing types are fixed simultaneously for a nominal taxon and for its nominotypical taxon, the fixation for the taxon at higher rank takes precedence.
61.2.2. When a nominal taxon in the family group, or the genus group, or the species group is raised or lowered in rank, or its name is used at more than one rank simultaneously, the name-bearing type remains the same [Arts. 36.2, 43.1, 46.2].
61.3. Name-bearing types and synonymy.
61.3.1. If nominal taxa with different name-bearing types are referred to a single taxonomic taxon, their names are subjective synonyms at the rank of that taxon (but need not be synonyms at a subordinate rank).
Example. The different name-bearing types of Psittacus elegans Gmelin, 1788 and Platycercus flaveolus Gould, 1837 are considered to belong to a single taxonomic species of rosella parrot of which Platycercus elegans (Gmelin, 1788) is the valid name. Although the names are subjective synonyms at the rank of species, they are not synonyms at the subordinate rank of subspecies of Platycercus elegans, for which the valid names are Pl. e. elegans (Gmelin, 1788) and Pl. e. flaveolus Gould, 1837.
61.3.2. If two or more objectively synonymous generic names have been used as the basis for names in the family group, the family-group names are objective synonyms.
61.3.3. If two or more nominal genus-group taxa have the same type species, or type species with different names but based on the same name-bearing type, their names are objective synonyms.
61.3.4. If two or more nominal species-group taxa have the same name-bearing type, their names are objective synonyms.
61.4. Designation of a subgenus or subspecies as a name-bearing type. If a nominal subgenus is fixed as the name-bearing type of a nominal family-group taxon, it is deemed to have been raised first to the rank of genus. If a nominal subspecies is fixed as the name-bearing type of a nominal genus-group taxon, it is deemed to have been raised first to the rank of species.
Example. Planigale Troughton, 1928 (Mammalia) was established with the species P. subtilissima (Lönnberg, 1913), P. tenuirostris Troughton, 1928 and P. ingrami (Thomas, 1906) and the subspecies P. ingrami brunnea Troughton, 1928. In the original description, the latter "subspecies of ingrami" was designated the type of Planigale by the term "Genotype". P. brunnea Troughton, 1928 is the type species by original designation, not P. ingrami (Thomas, 1906).
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