Source: http://iczn.ansp.org/wiki/Article59
Timestamp: 2019-04-20 02:28:02+00:00

Document:
Article 59. Validity of secondary homonyms.
59.1. Taxa considered congeneric. A species-group name while a junior secondary homonym must be treated as invalid by anyone who considers that the two species-group taxa in question are congeneric.
59.2. Secondary homonyms not replaced when no longer considered congeneric. If in a case of secondary homonymy the junior species-group name has not been replaced [Art. 60], and the relevant taxa are no longer considered congeneric, the junior name is not to be rejected, even if one species-group name was originally proposed in the current genus of the other.
Example. Zetterstedt (1855) established the new species Platyura nigriventris, which is now placed in the genus Orfelia. In 1910 Johannsen established the new species Apemon nigriventris, which was later referred to Platyura, its present position. The two species are not now treated as congeneric, and inasmuch as nigriventris (Johannsen) was never renamed in Platyura, a substitute name is not necessary.
59.3. Secondary homonyms replaced before 1961 but no longer considered congeneric. A junior secondary homonym replaced before 1961 is permanently invalid unless the substitute name is not in use and the relevant taxa are no longer considered congeneric, in which case the junior homonym is not to be rejected on grounds of that replacement.
Example. Deignan (1947) on taxonomic grounds merged the avian genera Muscicapa Brisson, 1760, Ficedula Brisson, 1760 and Niltava Hodgson, 1837 and took the first name as valid. He replaced seven resulting junior secondary homonyms, but because his classification and substitute names are not in use the species-group names that were replaced are not to be rejected under this Article.
59.3.1. If the use of a substitute name for a junior secondary homonym is a cause of confusion, the case is to be referred to the Commission for a ruling (under the plenary power if necessary, see Article 81) as to which name will, in its judgment, best serve stability and universality, and that name is then the valid name.
59.4. Reinstatement of junior secondary homonyms rejected after 1960. A species-group name rejected after 1960 on grounds of secondary homonymy is to be reinstated as valid by an author who considers that the two species-group taxa in question are not congeneric, unless it is invalid for some other reason.
Example. Aus niger Smith, 1950, if transferred after 1960 to Bus, becomes a junior secondary homonym of Bus niger Dupont, 1940, and is renamed Bus ater Jones, 1970. However, an author who does not consider that the two species are congeneric is to reinstate niger Smith as the valid specific name for the species concerned, with ater Jones as a junior synonym.
FranciscoWelterSchultes Art. 59.3 was once again critically commented in the [iczn-list] forum, 22 Sept 2012. M. Alonso-Zarazaga affirmed that the rule was not applied in Coleoptera. It creates the same category of problems as in Art. 23.9.5 (see my detailed comment there).
The mix-up of taxonomy and nomenclature was also addressed in a comment by Chris Thompson who emphasized that those in the 4th edition Committee who promoted these Articles did not consider that in zoology there does not exist an officially approved taxonomy.
FranciscoWelterSchultes CouldNotLock error in Art. 57 and Art. 58. I am trying to insert this here.
A name first mentioned as a junior synonym and later validated under Art. 11.6.1 takes the lowest rank of any mentioned species-group names.
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. This would conribute to help reducing a little the burden created by Art. 11.6.1 in so many molluscan names.
I have no example for this case, but 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 such cases.
FranciscoWelterSchultes Art. 59.3 should be removed (and replaced by the provisions of Art. 59.4 which should extend to before 1961) or substantially modified as proposed below.
The general problem is Art. 59.3 is that taxonomy and nomenclature are mixed up, and that the Code rules only nomenclature, not taxonomy. The use of the present tense ("is" not in use) is not applicable, and should be replaced by objectively determinable terms.
How much time must pass away that we can say "the name was used in the past and is no longer used now", so that the widely used name can be used again? 2 years? 20 years? Does it depend from the frequency with which the name is mentioned in the literature? In which kind of literature?
A solution would be to copy and paste the provisions of Art. 23.9 for the situation here. It would be good to have an objectively determinable provision, which name should be used for a species.
"59.3. Secondary homonyms replaced before 1961 but no longer considered congeneric. A species-group name rejected before 1961 on grounds of secondary homonymy is to be reinstated as valid by an author who considers that the two species-group taxa in question are not congeneric, unless it is invalid for some other reason.
An author who discovers that a junior secondary homonym was replaced before 1961 and the substitute name has recently been used by many authors should cite the two names together and state explicitly that the younger name should be used for the taxon, and that the action is taken in accordance with this Article; at the same time the author must give evidence that to his or her knowledge, the condition in Article 23.9.1.2 applies. From the date of publication of that act the younger name has precedence over the older name. When cited, the younger name may be qualified by the term nomen protectum and the older name by the term nomen oblitum (see Glossary)."
The Code does not know an example where Art. 59.3 is actually applied and necessary. I do not know any case either. I know some cases where Art. 59.3 has only caused trouble.
Glischrus caelata Studer, 1820 (Gastropoda, currently in the genus Trochulus) was once classified in Helix and became a junior secondary homonym of Helix caelata [Vallot], 1801 (currently in genus Candidula). Studer's name was replaced by Helix glypta Locard, 1880, a name that since then has very rarely been used (the genus Helix was split up shortly after). Falkner 1996 considered Glischrus caelata as permanently invalid. Turner et al. 1998 announced to refer the case to the Commission, but this never happened. The species is known under the name Trochulus caelatus, the community did not follow Falkner's action.
Balea cyclostoma Bielz, 1858 (Gastropoda, currently in genus Alopia) was established for a species from Romania, not Clausilia cyclostoma Pfeiffer, 1850 from Korea. Most contemporary authors (Pfeiffer, Westerlund, Bielz, Clessin, Kimakowicz) classified Balea and Clausilia as different genera, except Kobelt who classified both species in Clausilia and in 1879 used a substitute name Clausilia pomatias Pfeiffer, 1868 (or 1865, depends on your personal interpretation of Art. 11.6) for Balea cyclostoma Bielz. After 1900 most local authors (Sóos 1928, Grossu 1955, Szekeres 1969, Grossu 1981) have used Balea cyclostoma, but suddenly Nordsieck 2008 used again Clausilia pomatias.
The examples demonstrate that Art. 59.3 has been used to threaten the stability of nomenclature.

References: Art. 59
 Art. 23
 Art. 57
 Art. 58
 Art. 11
 Art. 11
 Art. 11
 Art. 59
 Art. 59
 Art. 59
 Art. 23
 Art. 59
 Art. 59
 Art. 11
 Art. 59