Type Method or Typification in Taxonomy

Type method is a legal device to provide the correct name for a taxon. The name of different taxonomic groups is based on the type method, by which a certain representative of the group is the source of the name for the group. This representative is called the nomenclature type or simply the type, and methodology is typification.

According to Article 9 of ICBN the type of a genus is a species (e.g. the type of genus Vernonia is V. noveboracensis (L.) Michx.), and the type of a family is a genus (e.g Aster is the type genus of Asteraceae).

The code recognizes several kinds of types, depending on the way in which a type specimen is selected. Several kinds of types designated by ICBN are included. These include -

• Holotype- It is a specimen used by the author in the original publication as the nomenclature type

Or

A particular specimen or illustration designated by the author to represent the type of a species. It is now essential to designate a holotype when publishing a new species.

Isotype:  It is a duplicate specimen of the holotype, i.e from the same collection, with the same locality, date, and number as the holotype.

Or

A specimen which is a duplicate of the holotype, collected from the same place, same time and by the same person. Often the collection number is also the same, differentiated as a, b, c, etc.

Nomenclature type: It is that element with which the name of a taxon is permanently associated.

Syntype: It is one of the two or more specimens cited by an author of a species when no holotype was designated; or, a syntype is any one of the two or more specimens originally designate as types.

Or

Any one of the two or more specimens cited by the author when no holotype was designated, or any one of the two or more specimens simultaneously designated as types.

Paratype or ‘’Co-types’’: It is a specimen other than isotype or holotype. If two or more specimens have been cited as types by the author, the remaining cited specimens are called co types or paratypes.

Or

A paratype is a specimen cited in the protologue that is neither the holotype nor an isotype, nor one of the syntypes if two or more specimens were simultaneously designated as types.

Lectotype: It is a specimen selected by a competent worker from the original material studied by the author of the species, when no holotype was designated, or when the holotype has been destroyed or lost.

 Or

A specimen or other element selected from the original material cited by the author when no holotype was originally selected or when it no longer exists. A lectotype is selected from isotypes, paratypes or syntypes.

 Neotype: It is a specimen selected to serve as a substitute for the holotype when all material, on which the name of the taxon was based, is missing.

Or

A specimen or illustration selected to serve as nomenclatural type as long as all of the material on which the name of the taxon was based is missing A specimen or an illustration selected when no holotype, isotype, paratype, or syntype exists.

Epitype: A specimen or illustration selected to serve as an interpretative type when the holotype, lectotype or previously designated neotype, or all original material associated with a validly published name is demonstrably ambiguous and cannot be critically identified for purposes of the precise application of the name of a taxon. When an epitype is designated, the holotype, lectotype, or neotype that the epitype supports must be explicitly cited.

Topotype: It is a specimen collected from the same locality from where the holotype was collected.

Or

Topotype is often the name given to a specimen collected from the same locality from which the holotype was originally collected.