Names of zoological taxa are governed by a set of laws, the International Code of Zoological Nomenclature or ICZN. In contrast to taxonomy, where decisions are based on interpretations, the laws of nomenclature are explicit and must be obeyed. One of the consequences, as discussed herein, is that paranomenclature, that reflects parataxonomic classifications based on parts of organisms independently of other parts, is not recognized under the ICZN and thus cannot be applied to formally diagnosed taxa. In the case of jawed polychaete annelids, parataxonomic treatments of the jaw elements as well as ICZN-governed naming of the reconstructed apparatus has divided their fossil record into separate but biologically overlapping groups of element-based and apparatus-based taxa. The independent treatment of groups created in this way has the potential for much confusion, if their names are used in formal systematics. Other recommendations of ICZN for effective diagnosis and illustration should also be considered in proposing names within groups such as this, where paranomenclature has been customary in the past.