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Inbinomial nomenclature, anomen dubium (Latin for "doubtful name", pluralnomina dubia) is a scientific name that is of unknown or doubtful application.
In case of anomen dubium, it may be impossible to determine whether a specimen belongs to that group or not. This may happen if the original type series (i.e.holotype,isotype,syntype orparatype) is lost or destroyed. The zoological and botanical codes allow for a new type specimen, orneotype, to be chosen in this case.
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A name may also be considered anomen dubium if itsname-bearing type is fragmentary or lacking important diagnostic features (this is often the case for species known only as fossils). To preserve stability of names, theInternational Code of Zoological Nomenclature allows a new type specimen, or neotype, to be chosen for anomen dubium in this case.
75.5. Replacement of unidentifiable name-bearing type by a neotype. When an author considers that the taxonomic identity of a nominal species-group taxon cannot be determined from its existing name-bearing type (i.e. its name is anomen dubium), and stability or universality are threatened thereby, the author may request the Commission to set aside under its plenary power [Art. 81] the existing name-bearing type and designate a neotype.[1]
For example, thecrocodile-likearchosaurian reptileParasuchus hislopiLydekker, 1885 was described based on apremaxillaryrostrum (part of the snout), but this is no longer sufficient to distinguishParasuchus from its close relatives. This made the nameParasuchus hislopi anomen dubium. In 2001 a paleontologist proposed that a new type specimen, a complete skeleton, be designated.[2] TheInternational Commission on Zoological Nomenclature considered the case and agreed in 2003 to replace the original type specimen with the proposed neotype.[3]
Inbacteriological nomenclature,nomina dubia may be placed on the list of rejected names by the Judicial Commission. The meaning of these names is uncertain. Other categories of names that may be treated in this way (rule 56a) are:[4]
Inbotanical nomenclature the phrasenomen dubium has no status, although it is informally used for names whose application has become confusing. In this regard, its synonymnomen ambiguum is of more frequent use.[5] Such names may be proposed forrejection.