basionnamen

Basionym (plural basionyms) is the original scientific name given to a taxon at its first description. It serves as the source name for any later name that reclassifies or re-ranks the taxon, such as when a species is moved to a different genus. The basionym is important because it anchors the taxon's identity and its authorship in the nomenclatural record.

In practice, when a taxon is transferred to another genus or its rank is changed, the new name is formed as a new combination that uses the same epithet (in most cases) and cites the basionym. The authorship of the basionym is retained in parentheses in the citation of the new name. For example, if a species originally described as Examplea alpha Smith, 1900 is later placed in genus Newgenus, the name becomes Newgenus alpha (Smith, 1900). The original Examplea alpha Smith, 1900 remains the basionym for the purpose of nomenclatural credit and reference.

Basionyms help maintain stability and traceability in taxonomy. They are distinct from other synonyms in that a basionym is the earliest legitimate name upon which a later name is based, whereas other synonyms are alternative names that refer to the same taxon but were not the basis for a later combination. The concept is used in both zoological and botanical nomenclature, with codes governing how basionyms are cited and how changes are documented.