International Code of Zoological Nomenclature
The International Code of Zoological Nomenclature is a system of rules designed to foster stability of scientific names for animals. Rules deal with such topics as the definition of publication, authorship of new scientific names, and types of taxa. Much of the code is based on the Principle of Priority, which states that the first validly described name for a taxon is the name to be used. Most of the rules deal with groups at the family level and below. Interpretations of the code and exceptions to it are controlled by the International Commission of Zoological Nomenclature, members of which are distinguished systematists who specialize indifferent taxonomic groups.
Species and subspecies are based on type specimens, the specimens used by an author in describing new taxa at this level. Type specimens should be placed in permanent archival collections (see below) where they can be examined by future researchers. Primary types include: (i) the holotype, the single specimen upon which the description of a new species is based; (ii) the lectotype, a specimen subsequently selected to be the primary type from a number of syntypes(a series of specimens upon which the description of a new species was based before the code was changed to disallow this practice); (iii) the neotype, a replacement primary type specimen that is permitted only when there is strong evidence that the original primary type specimen was lost or destroyed and when a complex nomenclatorial problem exists that can only be solved by the selection of a neotype.
Secondary types include paratypes, additional specimens used in the description of a new species, and paralectotypes, the remainder of a series of syntypes when a lectotypehas been selected from the syntypes. Among the many other kinds of types, mention should also be made of the topotype, a specimen taken from the same locality as the primary type and, therefore, useful in understanding variation of the population that included the specimen upon which the description was based, and the allotype, a paratypeof opposite sex to the holotype and useful in cases of sexual dimorphism.
Taxa above the species level are based on type taxa. For example, the type species of a genus is not a specimen but a particular species. Similarly, a family is based on a particular genus.