Open nomenclature is a vocabulary of partly informal terms and signs in which a taxonomist may express remarks about their own material. This is in contrast to synonymy lists, in which a taxonomist may express remarks on the work of others. Commonly such remarks take the form of abbreviated taxonomic expressions in biological classification.
Usage of open nomenclature
The expressions most commonly used are aff., cf., ?, and sp.. There is no strict convention that dictates where researchers place expressions such as aff. and cf. in the Latin name of a species or other taxon, and this may lead to difficulties of interpretation. However, the most significant unsettled issues concern the way that their meanings are to be interpreted. The International Code of Zoological Nomenclature (ICZN) makes no reference to open nomenclature, leaving its use and meaning open for interpretation by taxonomists.
- The expression aff. generally expresses the opinion that a potentially new and undescribed species has affinities with a known species.
- sp. (or spp. for the plural) indicates a potentially new species without remarking on possible affinities. This suggests either that identification has not yet been completed or that currently available evidence and material are insufficient to allocate the specimens to relevant known taxa, or alternatively, that as yet the specimen cannot be assigned to a new taxon of its own with sufficient confidence.
- The expressions cf. and ? signify varying degrees or types of uncertainty; unfortunately different authors have different usage habits, and cf. is used in other applications as well as open nomenclature, so the intended significance of the term must be interpreted with reserve. "Cf.", for Latin confer, means "compare with", and in more recent usage indicates greater uncertainty (than use of the question mark) in attributing the specimen to the taxon.
- Vidimus, Latin for "we have seen", usually is abbreviated to v. When present, it means that the author(s) have inspected the original type specimens, and so are basing their work and their statements on first-hand experience. Sometimes the opposite is expressed as non vidimus or non v, meaning that the original was not seen, or has never been observed, as is the case with of many kinds of fungal spore for instance.
- Incertae sedis, a taxon of uncertain position in a classification
- Nomen dubium (nomen ambiguum), a name of unknown or doubtful application
- Nomen novum a new name, usually to replace a name that in some way is unacceptable, say because it is a junior synonym)
- Nomen nudum an apparent taxon name, usually in the correct binomial form, but invalid, for instance because of not having been published with an adequate description.
- Species inquirenda, a species that in the opinion of the taxonomist requires further investigation
- Similar Latin terms in the glossary of scientific naming
- S. C. Matthews (1973), "Notes on open nomenclature and on synonymy lists" (PDF), Palaeontology 16 (4): 713–719, retrieved 24 March 2016
- Bengtson 1988, p. 223.
- Bengtson 1988, p. 224.