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Aholotype (Latin:holotypus) is a single physical example (or illustration) of anorganism used when thespecies (or lower-rankedtaxon) wasformally described. It is either the single such physical example (or illustration) or one of several examples, but explicitly designated as the holotype. Under theInternational Code of Zoological Nomenclature (ICZN), a holotype is one of several kinds ofname-bearing types. In theInternational Code of Nomenclature for algae, fungi, and plants (ICN) and ICZN, the definitions of types are similar in intent but not identical in terminology or underlying concept.
For example, the holotype for the butterflyPlebejus idas longinus is a preserved specimen of that subspecies, held by theMuseum of Comparative Zoology atHarvard University. Inbotany andmycology, anisotype is a duplicate of the holotype, generally pieces from the same individual plant or samples from the same genetic individual.
A holotype is not necessarily "typical" of that taxon, although ideally it is. Sometimes just a fragment of an organism is the holotype, particularly in the case of afossil. For example, the holotype ofPelorosaurus humerocristatus (Duriatitan), a largeherbivorous dinosaur from the earlyCretaceous period, is a fossil leg bone stored at theNatural History Museum inLondon. Even if a better specimen is subsequently found, the holotype is not superseded.
Under the ICN, an additional and clarifying type could be designated anepitype under article 9.8, where the original material is demonstrably ambiguous or insufficient.
Aconserved type (ICN article 14.3) is sometimes used to correct a problem with a name which has been misapplied; this specimen replaces the original holotype.
In the absence of a holotype, another type may be selected, out of a range of different kinds of type, depending on the case, alectotype or aneotype.
For example, in both the ICN and the ICZN a neotype is a type that was later appointed in the absence of the original holotype. Additionally, under the ICZN the commission is empowered to replace a holotype with a neotype, when the holotype turns out to lack important diagnostic features needed to distinguish the species from its close relatives. For example, the crocodile-likearchosaurian reptileParasuchus hislopiLydekker, 1885 was described based on apremaxillaryrostrum (part of the snout), but this is no longer sufficient to distinguishParasuchus from its close relatives. This made the nameParasuchus hislopi anomen dubium. Indian-American paleontologistSankar Chatterjee proposed that a newtype specimen, a complete skeleton, be designated.[1] TheInternational Commission on Zoological Nomenclature considered the case and agreed to replace the original type specimen with the proposed neotype.[2]
The procedures for the designation of a new type specimen when the original is lost come into play for some recent, high-profilespecies descriptions in which the specimen designated as the holotype was a living individual that was allowed to remain in the wild (e.g. a new species of capuchin monkey, genusCebus,[3] the bee speciesMarleyimyia xylocopae, or theArunachal macaqueMacaca munzala[4]). In such a case, there is no actual type specimen available for study, and the possibility exists that—should there be any perceived ambiguity in the identity of the species—subsequent authors can invoke various clauses in the ICZN Code that allow for the designation of a neotype. Article 75.3.7 of the ICZN[5] requires that the designation of a neotype must be accompanied by "a statement that the neotype is, or immediately upon publication has become, the property of a recognized scientific or educational institution, cited by name, that maintains a research collection, with proper facilities for preserving name-bearing types, and that makes them accessible for study", but there is no such requirement for a holotype.
