Type (biology)

In biology, a type is one particular specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to anchor or centralize the defining features of that particular taxon. In older usage (pre-1900 in botany), a type was a taxon rather than a specimen.

A taxon is a scientifically named grouping of organisms with other like organisms, a set that includes some organisms and excludes others, based on a detailed published description (for example a species description) and on the provision of type material, which is usually available to scientists for examination in a major museum research collection, or similar institution.

Type specimen

According to a precise set of rules laid down in the International Code of Zoological Nomenclature (ICZN) and the International Code of Nomenclature for algae, fungi, and plants (ICN), the scientific name of every taxon is almost always based on one particular specimen, or in some cases specimens. Types are of great significance to biologists, especially to taxonomists. Types are usually physical specimens that are kept in a museum or herbarium research collection, but failing that, an image of an individual of that taxon has sometimes been designated as a type. Describing species and appointing type specimens is part of scientific nomenclature and alpha taxonomy.

Type specimen (mineralogy)

In mineralogy, the type specimen, also known as type material, is a reference sample by which a mineral is defined.

Types

The following definitions for kinds of type specimens were approved in 1987 by the Commission on New Minerals and Mineral Names and the Commission on Museums of the International Mineralogical Association (IMA).

A holotype is a single specimen from which the original description of the mineral can be determined in whole.

Cotypes are multiple specimens from which quantitative, but not necessary, data are obtained for the original mineral description.

A neotype is a new specimen for the redefinition or reexamination of a mineral when the holotype or cotypes cannot be located or, upon examination, are inadequate for study.

Purpose

Type specimens are valuable when a mineral species is reevaluated because the original description of a mineral may be incomplete or contain errors.

History

Whereas the system of type specimens has long-existed in the biological sciences, this is not the case in mineralogy. The recentness of the practice means that sometimes no type material exists, even for minerals discovered as recently as the twentieth century. The publication of "Type specimens in mineralogy" by P.G. Embrey and M.H. Hey in 1970 stimulated much discussion on type specimens, leading to formal definitions approved by the IMA in 1987.