INTERNATIONAL CODE OF BOTANICAL NOMENCLATURE online

15.1. 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.

Ex. 1. Agaricus ericetorum Fr. was accepted by Fries in Systema mycologicum (1821), but later (1828) regarded by him as a synonym of A. umbelliferus L. and not included in his Index (1832) as an accepted name. Nevertheless A. ericetorum is a sanctioned name.

15.2. 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).

Ex. 2. 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.

Ex. 3. 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 taxonomic (heterotypic) synonym P. atricapillus (Batsch) Fayod, based on A. atricapillus Batsch (1786).

15.3. When, for a taxon from family to and including genus, two or more sanctioned names compete, Art. 11.3 governs the choice of the correct name (see also Art. 15.5).

15.4. When, for a taxon below the rank of 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.

Note 1. The date of sanctioning does not affect the priority (Art. 11) of a sanctioned name, which is determined only on the basis of valid publication. 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.

Ex. 4. 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.

15.5. A name which neither is sanctioned nor has the same type and final epithet as a sanctioned name in the same rank may not be applied to a taxon which includes the type of a sanctioned name in that rank the final epithet of which is available for the required combination (see Art. 11.4(b)).

15.6. Conservation (Art. 14) and explicit rejection (Art. 56.1) override sanctioning.

DIVISION II. RULES AND RECOMMENDATIONS
CHAPTER II. STATUS, TYPIFICATION, AND PRIORITY OF NAMES
SECTION 4. LIMITATION OF THE PRINCIPLE OF PRIORITY

Article 15

DIVISION II. RULES AND RECOMMENDATIONS CHAPTER II. STATUS, TYPIFICATION, AND PRIORITY OF NAMES SECTION 4. LIMITATION OF THE PRINCIPLE OF PRIORITY

Article 15

DIVISION II. RULES AND RECOMMENDATIONS
CHAPTER II. STATUS, TYPIFICATION, AND PRIORITY OF NAMES
SECTION 4. LIMITATION OF THE PRINCIPLE OF PRIORITY