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A conserved name or nomen conservandum (plural nomina conservanda, abbreviation nom. cons.) is a scientific name that has specific nomenclatural protection. Nomen conservandum is a Latin term, meaning a "name which should be conserved". The terms are often used interchangeably, such as by the International Code of Botanical Nomenclature,[1] while the International Code of Zoological Nomenclature favours "conserved name". The process for conserving botanical names is different from that for zoological names.
A nomen conservandum, although the term is not explicitly defined within the International Code of Botanical Nomenclature (ICBN), is "...any name of a genus, family, or taxon of intermediate rank that must be adopted in accordance with special legislation (Arts. 14, 15) as a correct name although otherwise contrary to the rules" (McVaugh et al., 1968). The principle of conservation has since been extended to specific names as well.
In botanical nomenclature, conservation is a nomenclatural procedure governed by Art. 14 of the ICBN. Its purpose is
Conservation is possible only for names at the rank of family, genus or species. Besides conservation of a name (Art. 14) the ICBN also offers the option of rejection of a name (Art. 56), creating a nomen rejiciendum (nom. rej., rejected name) that cannot be used anymore. Rejection is possible for a name at any rank.
Conservation may be restricted to the spelling of a name: Euonymus (not Evonymus), Guaiacum (not Guajacum), Hieronyma (not Hyeronima or Hieronima), etc. (see orthographical variant). Conservation may also concern the type of a name, thus fixing the application of that name to a taxon.
Conflicting conserved names are treated according to the normal rules of priority. Separate proposals (informally referred to as "superconservation" proposal) may be made to protect the latter of a conserved name that would be overtaken by another. However, conservation does not have the same consequences depending on the type of name that is conserved:
A name that has been rejected versus a conserved name under article 14 has no more nomenclatural consequence than one that has been rejected under article 56.
In the course of time there have been different standards for the majority required for a decision. However, for decades the Nomenclature Section has required a 60% majority for an inclusion in the Code, and the Committees have followed this example, in 1996 adopting a 60% majority for a decision.
For zoology, the term "conserved name", rather than nomen conservandum, is used in the International Code of Zoological Nomenclature, although informally both terms are used interchangeably.
In the glossary of the International Code of Zoological Nomenclature (the Code for names of animals, one of several Nomenclature Codes), this definition is given:
This is a more generalized definition than the one for nomen protectum, which is specifically a conserved name that is either a junior synonym or homonym, and would therefore ordinarily be considered invalid.
An example of a conserved name, one that is also a nomen protectum, is the dinosaur genus name Pachycephalosaurus, which was formally described in 1943. Later, Tylosteus (which was formally described in 1872) was found to be the same genus as Pachycephalosaurus (a synonym). By the usual rules, the genus Tylosteus has precedence and would normally be the correct name. But the International Commission on Zoological Nomenclature (ICZN) ruled that the name Pachycephalosaurus was to be given precedence and treated as the valid name, because it was in more common use and better known to scientists.
The ICZN's procedural details are different from those in botany, but the basic operating principle is the same, with petitions submitted for review by the Commission.