Source: http://iczn.ansp.org/wiki/Article24
Timestamp: 2019-04-20 02:47:29+00:00

Document:
Article 24. Precedence between simultaneously published names, spellings or acts.
24.1. Automatic determination of precedence of names. When homonyms or synonyms are established simultaneously, but proposed at different ranks, in the family group, genus group or species group the name proposed at higher rank takes precedence [Arts. 55.5, 56.3, 57.7]. See Article 61.2.1 for the precedence of simultaneous but different type fixations for taxa and their nominotypical subordinate taxa.
Example. The simultaneously established species-group names vulgaris Schmidt and sinensis Chang are considered to be synonyms; sinensis, proposed for a species, takes precedence over vulgaris because the latter was proposed for a subspecies.
24.2. Determination by the First Reviser.
24.2.1. Statement of the Principle of the First Reviser. When the precedence between names or nomenclatural acts cannot be objectively determined, the precedence is fixed by the action of the first author citing in a published work those names or acts and selecting from them; this author is termed the "First Reviser".
24.2.2. Determination of precedence of names or acts by the First Reviser. If two or more names, different or identical, and based on the same or different types, or two or more nomenclatural acts, are published on the same date in the same or different works, the precedence of the names or acts is fixed by the First Reviser unless Article 24.1 applies.
Example. The names Strix scandiaca and S. nyctea (Aves) were published together by Linnaeus (1758) and are considered to be subjective synonyms. Lönnberg (1931) acted as First Reviser and gave precedence to the name Strix scandiaca; thus, the valid name for the species (the Snowy Owl) is Nyctea scandiaca (Linnaeus, 1758) rather than N. nyctea (Linnaeus, 1758).
24.2.3. Selection of correct original spellings. If a name is spelled in more than one way in the original work, the first author to have cited them together and to have selected one spelling as correct is the First Reviser. The selected spelling (if not incorrect under Articles 32.4. or 32.5) is thereby fixed as the correct original spelling; any other spelling is incorrect (and therefore unavailable [Art. 32.4]).
24.2.4. Original authors may be deemed to be First Revisers of spellings. When the author, or one of joint authors, of two different original spellings of the same name subsequently uses one of them as valid in a work (including the author's or publisher's corrigenda), and neither had previously been selected as the correct spelling by a First Reviser, the author is deemed to be the First Reviser, whether or not the author cites both spellings together (that used as valid becomes the correct original spelling).
24.2.5. Unnecessary action by a First Reviser. If it is shown subsequently that the precedence of names, spellings or acts can be objectively determined, the action of the First Reviser is nullified.
Recommendation 24A. Action of First Reviser. In acting as First Reviser in the meaning of this Article, an author should select the name, spelling or nomenclatural act that will best serve stability and universality of nomenclature.
Recommendation 24B. First Revisers choosing between identical names should follow contemporary attributions of authorship. Zoologists acting as First Revisers to determine the precedence of identical names published in the same or different works, and on the same day, are advised to follow attributions by the authors concerned if these are known (see Article 50.6).
The Principle of Priority requires that if a name in use for a taxon is found to be unavailable or invalid (BUT NOT TAXONOMICALLY MISAPPLIED) it must be SUBSTITUTED by the next oldest available name from among its synonyms, including the names of the contained taxa of the same group (e.g. subgenera within genera), providing that that name is not itself invalid. If the rejected name has no potentially valid synonym a new substitute name (see Article 60.3) must be established in its place.
Another suggestion concerns the term "new substitute name" used here and in Art. 60.3. If applicable, it should probably read "new replacement name".
FranciscoWelterSchultes Art. 24.2.1., Art. 24.2.3.
The term "to cite" is undefined and should explain more precisely what is meant.
It seems to me that it is usually understood that a reviser mentioned the two names or spellings (for example in a list of names, one name was used and the other one listed as a synonym), and this is usually recognised as a First Reviser act. In June 2015 on the [iczn-list] mailing list there was a short discussion about "to cite": does it mean that the correct original source must be given, or is it sufficient to mention only the names?
In 24.2.1. it should be sufficient to be clear from the contents that the two names are regarded as synonyms, and that one of them is preferred. Neither is it necessary to list the original source, nor is it an obstacle if incorrect subsequent spellings were used for the names.
In 24.2.3. the names must of course be spelled exactly (upper case/lower case differences can be disregarded), however also here it is not necessary to cite the bibliographic source.
In my experience this would reflect common usage.
FranciscoWelterSchultes Art. 23.9.5 should either be removed or modified.
This Article was critically discussed in the [iczn-list] listserver forum, 22 Sept 2012. Common consensus was that the Article is not very helpful and disturbs too much the taxonomic work. It creates unnecessary workload, confusion and undesired disputes. Similar problems were reported from experts working in various different animal groups.
If modified, the Article should replace the idea to ask the Commission for a ruling, by a rule that is oriented at the provisions in Art. 23.9.2. Art. 23.9.5 should only be employed for frequently used names.
Directing the community to write applications to the Commission implies creating unnecessary workload for the taxonomists and also for the Commission. It was considered to be easier to look at original combinations and derive the correct name from there, than to screen a lot of publications and to verify the usage history of two names.
Most species names in entomology and malacology are only very rarely used. The provision should not be applied for those names. Only the really frequently names (for which it is easy to find the 25 publications in the sense of Art. 23.9.2) should induce deviations from pure homonymy rules.
Another problem concerns the badly defined term "considered congeneric". 1900 was in a time when many big genera were split up and species were not any more considered congeneric after that. But this was not immediately accepted by all authors. An example is Kobelt who still in 1906 published a note that he considered the helicid subgroups as subgenera of Helix (Pilsbry had classified the Helix subgenera as separate genera in the 1890s). It is not clear if two species which belonged to different subgenera, were "considered congeneric" by Kobelt although he did not menition all the thousands of species in his short note published in 1906. Also, it is not clear if the two must be considered congeneric by one single author, or if the term includes situations by which two different authors could classify this species independently in the genus. The general problem in the thought behind this Article was identified by Chris Thompson in the lack of awareness of the 4th edition's Committee that the zoological science has always allowed various different opinions, and that there never existed an officially approved taxonomy at every single point in the timeline.
FranciscoWelterSchultes Art. 23.9.6 should be modified.
It should be explained if a pure and uncommented list of names of species occurring in a country (or mountain chain, ...) is admissible or not. A name listed in a Red List is usually equipped with some information concerning the category of threat, so this should be admissible (although literally taken we are also dealing with lists of names).
A name first mentioned as a junior synonym and later validated under Art. 11.6.1 takes the lowest rank of any mentioned names.
Example: Rossmässler (1835) established a name Clausilia ventricosa var. basileensis. In the same publication he mentioned a name Clausilia attenuata as a synonym of a species Clausilia plicatula. The name attenuata was later validated under Art. 11.6.1. For those who consider both taxa conspecific the name basileensis takes precedence because Rossmässler (1835) had used it for a taxon, while attenuata had only been mentioned as a synonym.
Currrently the procedure is unclear. Some would argue that the synonym attenuata was not "proposed" at all as demanded by Art. 24.1, but only cited or mentioned as a synonym. Others would argue that the subspecific name basileensis was used at a lower rank than the specific name plicatula name for which attenuata was given as a synonym.
This would be the same solution as I proposed for the homonymy (Art. 57.7, comment deposited under Art. 59. because of a CouldNotLock error).
It would be useful to specify precedence for names which were validated under Art. 11.6.1. My proposal is to give names which were first mentioned as synonyms the lowest rank of all.
The more names are going to emerge out of the obscure literature (synonyms have never been recorded by indexers, every year new old synonyms are digged out and threaten widely used names), the more it gets likely to find more such cases. It would be useful to have as many as possible objective criteria for rejecting synonyms, to reduce the problems created by the ongoing findings of such synonyms.
Another rule would be very useful to clarify the conflict between simulateously established used names and synonyms which were later validated under Art. 11.6.1. Such a provision would help to reduce a little the enormeous burden created by the many molluscan names first published in synonymy. The content of this proposed new Article should be clear even without explicitly incorporating it into the Code, but it is necessary to include it because the experience tells stories of never ending disputes in such cases.
Original author deemed to be the First Reviser in case of synonyms validated later under Art. 11.6.1. If a name first published as a synonym was later vaidated under Art. 11.6.1, and in the original source was published another available name for the same taxon, then the original author is deemed to be the First Reviser to have selected the name which was used for this taxon in the original source.
Examples: Kaleniczenko (1851) established a new name Krynickillus (Gastropoda) and mentioned Krynickia as a synonym. Fischer (1856) used Krynickia and made this name available under Art. 11.6.1 from Kaleniczenko (1851). The First Reviser between the two simultaneously published available names is deemed to be Kaleniczenko (1851) who selected Krynickillus.
Des Moulins (1835) published a new name Pupa megacheilos var. pusilla and gave Pupa bigorriensis as a synonym for it. Pupa bigorriensis was later validated under Art. 11.6.1. The name pusilla takes precedence, selected by Des Moulins (1835) as First Reviser.
Rossmässler (1838) established Helix hispanica and mentioned a name balearica as a synonym. This synonym was later validated under Art. 11.6.1. Helix hispanica takes precedence, selected by Rossmässler (1838) who acted as First Reviser.
FranciscoWelterSchultes Art. 23.9.2 should be slightly modified.
"(...) ; at the same time the author must give direct evidence that the conditions of Article 23.9.1.2 are met (by citing bibliographically the 25 required references), and also (...)"
The expression "the author must give evidence" should be reworded in a stricter way. Dubois & Bour 2010 (Zootaxa 2447) thought that it was sufficient to provide one single reference to another paper Kabisch 1999 which had a long list of references in the involved animal group, in which the reader would certainly find 25 references as required by Art. 23.9.1.2. The Code should not encourage such a procedure. Art. 23.9 allows to set aside the Principle of Priority, this is a serious act and contrasts the very basic principles of zoological nomenclature. This should be taken as serious.
23.9.1.2 should specify how co-authorships are to be treated.
Replace "published by at least 10 authors" by "published by at least 10 authors (in co-authored works only the first authors can be counted)".
Art. 23.12 could possibly be removed.
I have no experience with cases where this article would be useful. In my opinion it makes the Code sound more confusing than necessary. Names were frequently declared to be nomen oblitums, not only in 1960-1973. Usually such statements in the literature are neglected. I see no reason why the statements between 1960 and 1973 should be treated otherwise. Art. 23b was obviously a step in the wrong direction and was removed later.
The example given under 23.7 is hardly intelligible and should be modified.
Krebs (1966) associated the footprints named Chirotherium by Kaup (1835) with the Triassic fossil reptile Ticinosuchus Krebs, 1965. Those authors who follow this view and consider Ticinosuchus and Chirotherium as synonyms must use the name Chirotherium.
FranciscoWelterSchultes Art. 23 is locked and I cannot set a comment under that page. So I try it here.
The name to be used for a taxon is the oldest available name applied to it, unless that name has been invalidated or another name is given precedence by any provision of the Code or by any ruling of the Commission.
If not absolutely necessary the term "valid" should not be used in the Code's text. The Code must be intelligible to a broad public, and the use of the term "valid" in the sense it is used by the ICZN is not in accordance with its widely established use in general English dictionaries and in botany. Using the term "valid" can lead to misunderstandings and confusion, this should be avoided.

References: Art. 60
 Art. 24
 Art. 24
 Art. 23
 Art. 23
 Art. 23
 Art. 23
 Art. 23
 Art. 11
 Art. 11
 Art. 24
 Art. 59
 Art. 11
 Art. 11
 Art. 11
 Art. 11
 Art. 11
 Art. 11
 Art. 11
 Art. 23
 Art. 23
 Art. 23

Art. 23
 Art. 23
 Art. 23