User:Darkfrog24/Type locality (biology)

Type specimen for Marocaster coronatus

In biology, a type is a specimen, or example, of a specific living thing or taxon, which is a group of specific living things. For example, if a scientist catches one frog that is not any species of frog already known, then that frog is the type of a new species of frog. That species will have a new scientific name. In older English writings from before 1900, plant scientists used the word type for groups of specific living things instead of specimens.

A taxon is a group of living things with a scientific name. Taxons can be small or large. A species is a taxon. A genus is a taxon. A kingdom is a taxon. Taxons are based on detailed, published descriptions and on type material. Scientists show the type material to other scientists so tehy can study it. They usually do this by putting the material in museums' research collections.

Type specimen

"Type specimen" redirects here. For the mineralogy term, see type specimen (mineralogy).

The International Code of Zoological Nomenclature (ICZN) and the International Code of Nomenclature for algae, fungi, and plants (ICN) make rules for type specimens. In these rules, the scientific name of every taxon is almost always based on just one specimen. Types are usually specimens that are kept in a museum or herbarium research collection. These types are usually whole organisms in a preservative, for example alcohol. Sometimes they are just pictures of the organisms. Describing species and appointing type specimens is part of scientific nomenclature and alpha taxonomy.

Depending on the naming code for the organism, a type can be a specimen, a culture, a drawn picture, or (for bacteria) a description.

For example, in the research collection of the Natural History Museum in London, there is a bird specimen numbered 1886.6.24.20. This is the specimen for the spotted harrier, Circus assimilis. This specimen is the holotype for that species; the name Circus assimilis is, by definition, the species of that particular specimen.

Scientists do not need to make sure that the specimen they use as a type is a "typical" individual in that taxon. The type can be a different color from other members of its taxon. It can be deformed or different.

The use of the term type is complicated because botany and zoology use it differently. In the PhyloCode, type-based definitions are replaced by phylogenetic definitions.

Older words

In some older books about taxonomy, writers use the word "type" differently. Some use it to mean "taxon."

In plants

In plant science names, a type (typus, nomenclatural type), "is that element to which the name of a taxon is permanently attached," meaning "the example that we use to give a species or other thing a name." (article 7.2) In plant science, a type is either an example of the plant or a drawing of the plant. The example plant is dead and treated with chemicals to make it not rot. The word for this is "curated." The specimen is in a herbarium, or plant museum. Here is when a drawing is enough :

• In the early days of plant taxonomy, before scientists could use chemicals to preserve plants. They could dry the plants, but then they could break if they were moved from place to place. Many early dried example plants are damaged or gone today. Plant scientists told very good artists to make good drawings with many details. Some of these drawings are so good that scientists still use them today.
• When the plant is so small that people cannot see it with their eyes. Scientists use drawings when they must look at the plant with a microscope, a machine that uses glass ovals to make things look bigger. A tiny "plant" on a microscope slide does not make a good type because the microscope slide may be lost and because the think the scientist wants is usually not the only thing on the microscope slide. (Art 37.5 of the Vienna Code, 2006).

Rules about types

1. Only a species or an infraspecific taxon can have a type of its own.
2. A genus's type is one of the types of the species in that genus (article 10).
3. A family has the same type as that of one of the genera in that family (article 10).

The ICN says the different kinds of types (article 9 and the Glossary), the most important of which is the holotype. These are

• holotype – the single specimen or illustration that the author(s) clearly indicated to be the nomenclatural type of a name
• lectotype – a specimen or illustration designated from the original material as the nomenclatural type when there was no holotype specified or the holotype has been lost or destroyed
• isotype – a duplicate of the holotype
• syntype – any specimen (or illustration) cited in the original description when there is no holotype, or any one of two or more specimens simultaneously designated as types
• paratype – any specimen (or illustration) cited in the original description that is not the holotype nor an isotype, nor one of the syntypes
• neotype – a specimen or illustration selected to serve as nomenclatural type if no material from the original description is available
• epitype – a specimen or illustration selected to serve as an interpretative type, usually when another kind of type does not show the critical features needed for identification

Note that the word "type" appears in botanical literature as a part of some older terms that have no status under the ICN: for example a clonotype.

In zoology

A gossamer-winged butterfly, Jamides elioti:
1) dorsal and 2) ventral aspect of holotype,
3) dorsal and 4) ventral aspect of paratype

In zoological nomenclature, the type of a species or subspecies is a specimen or series of specimens. The type of a genus or subgenus is a species. The type of a suprageneric taxon (e.g., family, etc.) is a genus. Names higher than superfamily rank do not have types. A "name-bearing type" is a specimen or image that "provides the objective standard of reference whereby the application of the name of a nominal taxon can be determined."

Definitions

• A type specimen is a vernacular term (not a formally defined term) typically used for an individual or fossil that is any of the various name-bearing types for a species. For example, the type specimen for the species Homo neanderthalensis was the specimen "Neanderthal-1" discovered by Johann Karl Fuhlrott in 1856 at Feldhofer in the Neander Valley in Germany, consisting of a skullcap, thigh bones, part of a pelvis, some ribs, and some arm and shoulder bones. There may be more than one type specimen, but there is (at least in modern times) only one holotype.
• A type species is the nominal species that is the name-bearing type of a nominal genus or subgenus.
• A type genus is the nominal genus that is the name-bearing type of a nominal family-group taxon.
• The type series are all those specimens included by the author in a taxon's formal description, unless the author explicitly or implicitly excludes them as part of the series.

Use of type specimens

Type illustration of Mormopterus acetabulosus

Although in reality biologists may examine many specimens (when available) of a new taxon before writing an official published species description, nonetheless, under the formal rules for naming species (the International Code of Zoological Nomenclature), a single type must be designated, as part of the published description.

A type description must include a diagnosis (typically, a discussion of similarities to and differences from closely related species), and an indication of where the type specimen or specimens are deposited for examination. The geographical location where a type specimen was originally found is known as its type locality. In the case of parasites, the term type host (or symbiotype) is used to indicate the host organism from which the type specimen was obtained.

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:

Holotype

See the main article: Holotype

When a single specimen is clearly designated in the original description, this specimen is known as the holotype of that species. The holotype is typically placed in a major museum, or similar well-known public collection, so that it is freely available for later examination by other biologists.

Paratype

See the main article: Paratype

When the original description designated a holotype, there may be additional specimens that the author designates as additional representatives of the same species, termed paratypes. These are not name-bearing types.

Allotype

An allotype is a specimen of the opposite sex to the holotype, designated from among paratypes. The word was also formerly used for a specimen that shows features not seen in the holotype of a fossil. The term is not regulated by the ICZN.

Neotype

A neotype is a specimen later selected to serve as the single type specimen when an original holotype has been lost or destroyed or where the original author never cited a specimen.

Syntype

See the main article: Syntype

A syntype is any one of two or more specimens that is listed in a species description where no holotype was designated; historically, syntypes were often explicitly designated as such, and under the present ICZN this is a requirement, but modern attempts to publish species description based on syntypes are generally frowned upon by practicing taxonomists, and most are gradually being replaced by lectotypes. Those that still exist are still considered name-bearing types.

Lectotype

A lectotype is a specimen later selected to serve as the single type specimen for species originally described from a set of syntypes. In zoology, a lectotype is a kind of name-bearing type. When a species was originally described on the basis of a name-bearing type consisting of multiple specimens, one of those may be designated as the lectotype. Having a single name-bearing type reduces the potential for confusion, especially considering that it is not uncommon for a series of syntypes to contain specimens of more than one species.

A notable example is a suggestion that Carl Linnaeus should constitute the lectotype for the species Homo sapiens.

Paralectotype

A paralectotype is any additional specimen from among a set of syntypes after a lectotype has been designated from among them. These are not name-bearing types.

Hapantotype

A special case in Protistans where the type consists of two or more specimens of "directly related individuals representing distinct stages in the life cycle"; these are collectively treated as a single entity, and lectotypes cannot be designated from among them.

Iconotype

An illustration on which a new species or subspecies was based. For instance, the Burmese python, Python bivittatus, is one of many species that are based on illustrations by Albertus Seba (1734).

Ergatotype

An ergatotype is a specimen selected to represent a worker member in hymenopterans which have polymorphic castes.

Hypotype

"Hypotype" redirects here. For the moth, see Hypotype (genus).

A hypotype is a specimen whose details have previously been published that is used in a supplementary figure or description of the species.

Alternatives to preserved specimens

Type illustrations have also been used by zoologists, as in the case of the Réunion parakeet, which is known only from historical illustrations and descriptions.

Recently, some species have been described where the type specimen was released alive back into the wild, such as the Bulo Burti boubou (a bushshrike), described as 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 a type specimen does not invalidate the name, but it may be necessary for the future to designate a neotype for such a taxon, should any questions arise. However, in the case of the bushshrike, ornithologists have argued that the specimen was a rare and hitherto unknown color morph of a long-known species, using only the available blood and feather samples. While there is still some debate on the need to deposit actual killed individuals as type specimens, it can be observed that given proper vouchering and storage, tissue samples can be just as valuable should dispute about the validity of a species arise.

Formalisation of the type system

The various types listed above are necessary because many species were described one or two centuries ago, when a single type specimen, a holotype, was often not designated. Also, types were not always carefully preserved, and intervening events such as wars and fires have resulted in the destruction of the original type material. The validity of a species name often rests 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 ICZN has existed only since 1961 when the first edition of the Code was published. The ICZN does not always demand a type specimen for the historical validity of a species, and many "type-less" species do exist. The current edition of the Code, Article 75.3, prohibits the designation of a neotype unless there is "an exceptional need" for "clarifying the taxonomic status" of a species (Article 75.2).

There are many other permutations and variations on terms using the suffix "-type" (e.g., allotype, cotype, topotype, generitype, isotype, isoneotype, isolectotype, etc.) but these are not formally regulated by the Code, and a great many are obsolete and/or idiosyncratic. However, some of these categories can potentially apply to genuine type specimens, such as a neotype; e.g., isotypic/topotypic specimens are preferred to other specimens, when they are available at the time a neotype is chosen (because they are from the same time and/or place as the original type).

The term fixation is used by the Code for the declaration of a name-bearing type, whether by original or subsequent designation.

Type species

See the main article: Type species

The common toad, Bufo bufo described by Linnaeus, is the type species for the genus Bufo

Each genus must have a designated type species (the term "genotype" was once used for this but has been abandoned because the word has become much better known as the term for a different concept in genetics). 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

See the main article: Type genus

A type genus is a 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 that has passed into synonymy; the family name does not need to be changed in such a situation.

See also

• Archetype
• Glossary of scientific naming
• Nomen dubium (zoology)
• Nomen nudum
• Genetypes – genetic sequence data from type specimens
• Pathotype – a type of intrasubspecific taxon of pathogenic bacteria
• Principle of typification

External links

• ICZN Code: International Code of Zoological Nomenclature, the official website
• Fishbase Glossary section (archived)
• A compendium of terms (archived)
• Zoological Type Nomenclature (Evenhuis) (PDF)

{{DEFAULTSORT:Type}} [[Category:Biology]] [[Category:Taxonomy]]