CHAPTER II. Status, typification, and priority of names
SECTION 4. Limitation of the principle of priority
Names sanctioned under Art. 13.1(d) are treated as if conserved against earlier homonyms and competing synonyms. Such names, once sanctioned, remain sanctioned even if elsewhere in the sanctioning works the sanctioning author does not recognize them. The spelling used by a sanctioning author is treated as conserved, except for changes mandated by Art. 60.
Agaricus ericetorum Pers. (1796) was accepted by Fries in Systema mycologicum (1821), but later (1828) regarded by him as a synonym of A. umbelliferus L. (1753) and not included in his Index (1832) as an accepted name. Nevertheless A. ericetorum Pers. : Fr. is a sanctioned name.
The spelling used in the sanctioned name Merulius lacrimans (Wulfen : Fr.) Schum. (1803) is maintained even though the basionym was originally published as Boletus “lacrymans” Wulfen (1781).
An earlier homonym of a sanctioned name is not made illegitimate by that sanctioning but is unavailable for use; if not otherwise illegitimate, it may serve as a basionym of another name or combination based on the same type (see also Art. 55.3).
Patellaria Hoffm. (1789) is an earlier homonym of the sanctioned generic name Patellaria Fr. (1822) : Fr. Hoffmann’s name is legitimate but unavailable for use. Lecanidion Endl. (1830), based on the same type as Patellaria Fr. : Fr., is illegitimate under Art. 52.1.
Agaricus cervinus Schaeff. (1774) is an earlier homonym of the sanctioned A. cervinus Hoffm. (1789) : Fr.; Schaeffer’s name is unavailable for use, but it is legitimate and may serve as basionym for combinations in other genera. In Pluteus Fr. the combination is cited as P. cervinus (Schaeff.) P. Kumm. and has priority over the heterotypic (taxonomic) synonym P. atricapillus (Batsch) Fayod, based on A. atricapillus Batsch (1786).
When, for a taxon in a rank from family to genus, inclusive, two or more sanctioned names compete, Art. 11.3 governs the choice of the correct name (see also Art. 15.5).
When, for a taxon in a rank lower than genus, two or more sanctioned names and/or two or more names with the same final epithet and type as a sanctioned name compete, Art. 11.4 governs the choice of the correct name.
The date of sanctioning does not affect the date of valid publication, and thus priority (Art. 11), of a sanctioned name. In particular, when two or more homonyms are sanctioned only the earliest of them may be used, the later being illegitimate under Art. 53.2.
Fries (Syst. Mycol. 1: 41. 1821) accepted Agaricus flavovirens Pers. (1793), treating A. equestris L. (1753) as a synonym. Later (Elench. Fung. 1: 6. 1828) he stated “Nomen prius et aptius arte restituendum” and accepted A. equestris. Both names are sanctioned, but when they are considered synonyms A. equestris, having priority, is to be used.
A name that neither is sanctioned nor has the same type and final epithet as a sanctioned name in the same rank may not be used for a taxon that includes the type of a sanctioned name in that rank with a final epithet that is available for the required combination (see Art. 11.4(b)).
Conservation (Art. 14) and explicit rejection (Art. 56.1) override sanctioning.