REPRINT Biological Nomenclature from Linnaeus to the PhyloCode

Linnaeus and other 18th Century naturalists practiced nomenclature in a way that associated taxon names more strongly with taxa (groups) than with the categorical ranks of the taxonomic (“Linnaean”) hierarchy. For those early naturalists, ranks functioned merely as devices for indicating hierarchical position that did not affect the application or spelling of taxon names. Consequently, taxa did not change their names simply because of changes in rank. For example, the name Reptilia did not change when the rank of the taxon designated by that name was changed from order to class. During the 19th Century, an alternative approach to nomenclature emerged that made rank assignment fundamental to the application and spelling of taxon names. Under this rank-based approach, which forms the basis of the current Zoological Code, names are implicitly defined in terms of ranks. As a consequence, names are more strongly associated with ranks than with taxa and thus taxa change their names simply because of changes in rank. For example, if the rank of the taxon Iguanidae is changed from family to superfamily, its name must change to Iguanoidea. A new approach to nomenclature, termed phylogenetic nomenclature, ties taxon names to explicitly evolutionary concepts of taxa through definitions that describe taxa in terms of ancestry and descent. This treebased approach to nomenclature once again associates taxon names more strongly with taxa than with ranks and thus represents a return to an approach similar to that practiced by Linnaeus and other early naturalists, updated with evolutionary principles.