[Taxacom] Descriptive suprafamilial names of plants

[Jim L. Reveal]

According to Art. 16 of International Code of Nomenclature for algae, fungi, and plants (ICN), names above the rank of family may be (a) automatically typified or (b) descriptive. Magnoliophyta is an automatically typified name, being based on the genus Magnolia which, in turn, is typified on a single species (M. virginiana). That epithet is typified on a single specimen and this is the only element that must be termed M. virginiana, Magnolia, Magnoliaceae, Magnoliales, Magnoliophyta, or any other suprageneric name based on the genus Magnolia. 

All other element associated with Magnolia virginiana, or any other taxon above that rank, including any other specimens, is strictly a taxonomic decision.

A descriptive name is not based on a generic name, may be used unchanged at different ranks, and may be defined however one may wish. Descriptive terms like Angiospermae, Gymnospermae, Coniferae, Centrospermae are circumscribe however one may wish and, in fact, have been. Some author define Coniferae to include all gymnosperms, but other restrict their concept to just the conifers. Centrospermae has been used for groups of algae as well as plants. Authorships are impossible to define as the addition or subtraction of any taxon alters the circumscription. Thus, such names violate Principle IV of ICN, at least in principle, that a taxon have "a particular circumscription, position, and rank" and "can bear only one correct name." 

Arguably, therefore, for a descriptive name to be used as proposed by the original author of the name, say Angiospermae, that author must have included in that group all possible taxa and no newly discovered entity can be added because to do so this would alter the original circumscription. Thus, the second author who proposes Angiospermae with a different circumscription creates a later homonym because, as required in Principle IV, the earliest name must be used.

Now, this is silly, of course, and today one actually applies the rules of nomenclature to descriptive names in the most general and purposefully vague ways as possible. Fortunately, no one questions any action and we all pretend that use of a specific descriptive name has been followed "in accordance with the rules."

Given the problems with descriptive name, I strongly urge that one use names that can be typified and that descriptive names should be used only as informal terms. Thus, Magnoliophyta or angiosperms; Pinophyta or gymnosperms. As Principle II states: "The application of names of taxonomic groups is determined by means of nomenclatural types."

Jim Reveal