Article 72. General provisions
The term "type" forms part of many compound terms used by taxonomists to distinguish between particular kinds of specimens, only some of which are name-bearing types. For the purposes of the Code, three categories of specimens are regulated, namely
72.1.1. type series: all the specimens on which the author established a nominal species-group taxon (with the exception of those excluded [Art. 72.4.1]); in the absence of holotype designation, or the designation of syntypes, or the subsequent designation of a lectotype, all are syntypes and collectively they constitute the name-bearing type;
72.1.2. name-bearing types: specimens with a name-bearing function, whether fixed originally (holotype [Art. 73.1] or syntypes [Art. 73.2]) or fixed subsequently (lectotype [Art. 74] or neotype [Art. 75]);
Recommendation 72A. Use of the term "allotype". The term "allotype" may be used to indicate a specimen of opposite sex to the holotype; an "allotype" has no name-bearing function.
A nominal species-group taxon established before 2000 may have its name-bearing type fixed from the type series [Art. 72.4] originally [Art. 73], or subsequently [Art. 74]. (If no name-bearing type is believed to be extant a neotype may be fixed; see Article 75 for conditions).
A proposal of a new nominal species-group taxon after 1999 (unless denoted by a new replacement name (nomen novum) [Arts. 16.4, 72.7]), must include the fixation of a holotype [Art. 16.4] (see Article 73.1) or syntypes [Art. 73.2]. In the case of syntypes, only those specimens expressly indicated by the author to be those upon which the new taxon was based are fixed as syntypes.
72.4.1. The type series of a nominal species-group taxon consists of all the specimens included by the author in the new nominal taxon (whether directly or by bibliographic reference), except any that the author expressly excludes from the type series [Art. 72.4.6], or refers to as distinct variants (e.g. by name, letter or number), or doubtfully attributes to the taxon.
18.104.22.168. For a nominal species or subspecies established before 2000, any evidence, published or unpublished, may be taken into account to determine what specimens constitute the type series.
Example. Linnaeus (1758) described the gastropod Conus imperialis, and cited specimens described or illustrated by previous authors. The type series included not only those cited specimens, but also two other specimens currently in collections in Uppsala and London of which there is evidence that they were known to Linnaeus and recognized by him as C. imperialis when the nominal species was established.
72.4.2. If a new nominal species-group taxon is based, in whole or in part, on a published misidentification by an earlier author, the type series consists of or includes the specimen or specimens which had been misidentified, whether the later author refers to them directly or through an illustration or a description (but see Recommendation 73B).
72.4.3. The type series of a nominal species-group taxon of which the name was first published as a junior synonym, but was made available before 1961 under the provisions of Article 11.6, consists of the specimen (or specimens) cited with that name in the published synonymy, or, if none was cited there, denoted by that name when it was adopted as the name of a taxon.
72.4.4. The type series of a nominal species-group taxon of which the name is made available by a bibliographic reference to a description or definition associated with an unavailable name [Arts. 12.2.1, 13.1.2] consists of or includes the specimen or specimens denoted by that unavailable name.
72.4.5. When an author designates a holotype [Art. 73.1], then the other specimens of the type series are paratypes. The latter do not become syntypes and cannot be used for lectotype selection [Art. 74] if the holotype is lost or destroyed; however, they are eligible for neotype selection (see Recommendation 75A).
72.4.6. If an author when establishing a nominal species-group taxon nominates either "syntypes" (by that term, or by use of one of the terms "cotypes" or "types" alone), or "holotype and paratypes" used together (or by use of the term "type" together with "allotype" or "cotypes"), and also lists other specimens, the separate mention of the latter expressly excludes them from the type series.
72.4.7. The mere citation of "Type" or equivalent expression, in a published work other than that in which the nominal species-group taxon is established, or in an unpublished catalogue of a museum, or on a label, is not necessarily evidence that a specimen is or is fixed as any of the kinds of types referred to in this Chapter.
Recommendation 72B. Express exclusion from the type series or syntypes. Authors excluding specimens from the type series (or from the syntypes) of new nominal species-group taxa should be explicit. For example, illustrating some, but not all, or indicating specimen numbers of one or some specimens, but not others, would not in itself exclude those specimens not illustrated or not numbered.
Only the following are eligible to be a name-bearing type, or part of a name-bearing type, of a nominal species-group taxon:
72.5.1. an animal, or any part of an animal, or an example of the fossilized work of an animal, or of the work of an extant animal if the name based on it was established before 1931;
72.5.2. a colony of animals that exists in nature as a single entity, derived by asexual or vegetative multiplication from a single individual (e.g. a colony of cnidarians, such as corals), or part of such a colony;
72.5.3. in the case of fossils, a natural replacement, natural impression, natural mould, or natural cast of an animal or colony, or part of either;
72.5.4. in extant species of protistans, one or more preparations of directly related individuals representing differing stages in the life cycle (a hapantotype) [Art. 73.3];
72.5.5. a preparation for microscope examination (e.g. a "type slide") containing one or more individual organisms, in which the name-bearing types are clearly indicated and identifiable.
Recommendation 72C. Marking of important individuals. Whenever possible, authors establishing new nominal species-group taxa based upon microscope preparations containing more than one specimen (a "type slide") should mark distinctly the locations of specimens which are considered to be of crucial importance in demonstrating the taxonomic characters.
72.5.6. In the case of a nominal species-group taxon based on an illustration or description, or on a bibliographic reference to an illustration or description, the name-bearing type is the specimen or specimens illustrated or described (and not the illustration or description itself).
The fact that a specimen is already the name-bearing type, or part of the name-bearing type, of one nominal species-group taxon does not prevent its being the name-bearing type, or part of the name-bearing type, of another.
If an author proposes a new species-group name expressly as a replacement (a nomen novum) for an earlier available one, then the two names are objective synonyms; both the nominal taxa they denote have the same name-bearing type despite any simultaneous restriction or application of the new replacement name (nomen novum) to particular specimens or any contrary designation of type, or any different taxonomic usage of the new replacement name.
Examples. Mus terraereginae Alston, 1879 was a new replacement name (nom. nov.) for Mus leucopus (Gray, 1867), a secondary homonym of Mus leucopus Rafinesque, 1818; accordingly, both have the same name-bearing type. Betpakodiscus aliminimus Brenckle, 1993 was established as a "nom. nov." for Archaediscus minimus Reitlinger, 1950 sensu Grozdilova & Lebedeva (1953). B. aliminimus and A. minimus do not have the same name-bearing type because "Archaediscus minimus Grozdilova & Lebedeva, 1953, non Reitlinger 1950" is not an available name (the name-bearing type of B. aliminimus Brenckle, 1993 is fixed through the provisions of Article 72.4.4).
If two or more nominal species-group taxa are included within a single taxonomic taxon at the same rank in the species-group, their respective name-bearing types remain unchanged (subject to Article 23, the valid name of the taxonomic taxon so formed is that of the nominal species-group taxon with the oldest potentially valid name).
Holotypes, syntypes, lectotypes and neotypes are the bearers of the scientific names of all nominal species-group taxa (and indirectly of all animal taxa). They are the international standards of reference that provide objectivity in zoological nomenclature and must be cared for as such (see Recommendations 72D to 72F). They are to be held in trust for science by the persons responsible for their safe keeping.
Recommendation 72D. Labelling of name-bearing types. Holotypes, syntypes, lectotypes and neotypes should be labelled in a way that will unmistakably denote their status.
Recommendation 72E. Publication of information on labels. An author who designates a holotype, lectotype, neotype or syntypes should publish all information that appears on the labels accompanying the specimens so as to facilitate the future recognition of the specimens.
Recommendation 72F. Institutional responsibility. Every institution in which name-bearing types are deposited should
72F.1 ensure that all are clearly marked so that they will be unmistakably recognized as name-bearing types;
72F.2 take all necessary steps for their safe preservation;
72F.3 make them accessible for study;
72F.4 publish lists of name-bearing types in its possession or custody; and
72F.5 so far as possible, communicate information concerning name-bearing types when requested.