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BOTANY In Botanical Nomenclature , a ''type'' (typus, nomenclatural type), "is that element to which the name of a taxon is permanently attached."Art 7.1 '' ICBN ''. A Botanical Name , by itself, is only a phrase (of one to three words). For a name to be meaningful it is necessary to be sure what it applies to. A type fixes a botanical name to a Taxon . In botany a type is either a specimen or an illustration. A specimen is a real plant (or one or more parts of a plant or a lot of small plants), dead and kept safe, "curated", in a herbarium (or the equivalent for fungi). Notable cases of where an illustration may serve as a type are (this is not an exclusive listing):
Note that a type only fixes a name to a single representative of the taxon. A type does not determine the circumscription of the taxon. For example, the common Dandelion is a controversial taxon: some botanists consider it to consist of over a hundred species, although most botanists regard it to be a single species. The type of the name ''Taraxacum officinale'' is the same whether the circumscription of the species includes all those small species (''Taraxacum officinale'' is a 'big' species) or whether the circumscription is limited to only one small species among the other hundred (''Taraxacum officinale'' is a 'small' species). In this case the name ''Taraxacum officinale'' is the same and the type of the name is the same, but the extent of what the name actually applies to varies strongly. Setting the circumscription of a taxon is done by a taxonomist in a publication. Miscellaneous notes: # Usually, only a species or an Infraspecific Taxon can have a type of its own. For a new taxon (published on or after 1 January 1958) at these ranks a type should not be an illustration. # A genus (almost always) has the same type as that of one of its species. For convenience this species may, unofficially, be called its '' Type Species '', a phrase that has no standing under the ''ICBN''. Only by Conservation may a genus have its own type. # A family has the same type as that of one of its genera (that is, almost always the type of a species). For convenience this genus may, unofficially, be called its '' Type Genus '', a phrase that has no standing under the ''ICBN''. # The ''ICBN'' provides a listing of the various kinds of type in Art 9 , the most important of which is the . ZOOLOGY In Zoological Nomenclature , a type is a specimen or a taxon. A "name-bearing type" "provides the objective standard of reference whereby the application of the name of a nominal taxon can be determined." Definitions
Use of types Although in reality biologists may examine many specimens (if available) of a new taxon in coming up with a written species description, under the formal rules for naming species (the International Code Of Zoological Nomenclature ), a single type should be designated. When a single specimen is designated in the original description as the type for a species it is called a ''' Holotype '''. The holotype is typically stored in a museum or other collection to be available for later examination by other biologists as needed. Included in the type description should be a discussion of similarities to and differences from closely related species and where a type specimen or specimens are deposited for examination. The geographical location where a type specimen originated is known as its '''type locality''' or '''type location'''. Zoological collections are maintained by universities and museums. Ensuring that types are kept in good condition and made available for examination by taxonomists are two important functions of such collections. And, while there is only one ''holotype'' designated, there can be other "type" specimens, the following of which are formally defined:
The various types listed above are needed because many species descriptions go back one or two centuries and holotype designation was not always done, types were not always well kept or preserved, or intervening events have resulted in destruction of original type material. The validity of a species name can rest upon the availability of original type specimens; or, if the type cannot be found, or one has never existed, upon the clarity of the description. The ''', Article 75.3, prohibits the designation of a Neotype unless there is "an exceptional need" for "clarifying the taxonomic status" of a species; as the status and identity of ''H. sapiens'' is not questioned, there is no exceptional need for clarification, and "any such neotype designation is invalid" (Article 75.2). Recently some species have been described where the type specimen was released alive back into the wild, such as the Bulo Burti Bush-shrike ('' Laniarius Liberatus ''), in which the species description included DNA sequences from blood and feather samples. Assuming there is no future question as to the status of such a species, the absence of the type specimen does not invalidate the name, but it may be necessary in the future to designate a neotype for such a taxon, should any questions arise. There are many other permutations and variations on terms using the suffix "-type" (e.g., Allotype , Cotype , Topotype , Generitype , Isoneotype , etc.) but these are not formally regulated by the Code, and a great many are obsolete and/or idiosyncratic. The term fixation is used by the Code for the declaration of a name-bearing type, whether by original or subsequent designation. Type species Each genus must have a designated type species (the term "genotype" was once used for this but has been abandoned because the word has been co-opted for use in Genetics , and is much better known in that context). The description of a genus is usually based primarily on its type species, modified and expanded by the features of other included species. The generic name is permanently associated with the name-bearing type of its type species. Ideally, a type species best exemplifies the essential characteristics of the genus to which it belongs, but this is subjective and, ultimately, technically irrelevant, as it is not a requirement of the Code. If the type species proves, upon closer examination, to belong to a pre-existing genus (a common occurrence), then all of the constituent species must be either moved into the pre-existing genus, or disassociated from the original type species and given a new generic name; the old generic name passes into synonymy, and is abandoned, unless there is a pressing need to make an exception (decided case-by-case, via petition to the International Commission On Zoological Nomenclature ). Type genus A type genus is that genus from which the name of a Family or subfamily is formed. As with type species, the type genus is not necessarily the most representative, but is usually the earliest described, largest or best known genus. It is not uncommon for the name of a family to be based upon the name of a type genus which has passed into synonymy; the family name does not need to be changed in such a situation. SEE ALSO EXTERNAL LINKS
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