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Re: Typical and less typical types
Short history of Art. 23b / 23.9.
The term nomen oblitum and the '50-year rule' (Art. 23b) were introduced
in the second edition of the ICZN (in force since 1961) and an expanded
version (including a qualifying clause to determine common usage: at least
5 different authors in at least 10 publications) replaced it through a
ruling by the Commission since 1970.
The third edition (1985) reduced the former Article 23b to a statement of
the purpose of the principle of priority (" ... not intended to be used to
upset a long-accepted name ... ") and an Article 79c containing the
qualifying clauses for a ruling by the Commission (older name not used
during preceding 50 years, junior name in use by at least 5 different
authors in at least 10 publications, etc.).
The fourth edition (1999) returned responsibility for certain cases to
individual authors; however, the qualifying clauses are much more rigid
than before. Art. 23.9. reads:
"23.9. Reversal of precedence. In accordance with the purpose of the
Principle of Priority [Art. 23.2.], its application is moderated as
23.9.1. prevailing usage must be maintained when the following conditions
are both met:
188.8.131.52. the senior synonym or homonym has not been used as a valid name
after 1899, and
184.108.40.206. the junior synonym or homonym has been used for a particular
taxon, as its presumed valid name, in at least 25 works, published by at
least 10 authors in the immediately preceding 50 years and encompassing a
span of not less than 10 years.
23.9.2. An author who discovers that both the conditions of 23.9.1 are met
should cite the two names together and state explicitly that the younger
name is valid, and that the action is taken in accordance with this
Article; at the same time the author must give evidence that the
conditions of Article 220.127.116.11 are met, and also state that, to his or her
knowledge, the condition in Article 18.104.22.168. applies. ...
23.9.6. The deliberate use of a name contrary to Art. 23.9.1, or the
mentioning of a name in a synonymy, or its mere listing in an abstracting
publication, or in a nomenclator or other index or list of names must not
be taken into account in determing usage under Art. 22.214.171.124 and
In all other cases, when the precedence should be reversed, still a ruling
by the Commission is required.
Dr. Markus Moser
Staatliches Museum fuer Naturkunde Stuttgart
Museum am Loewentor (= Rosenstein 1)
> Only one fine point has been missed :-). The '50-year rule' (that a
> can be automatically suppressed in favour of a junior synonym if it hasn't
> been used for over 50 years, and the preferred name has been used in at
> least 25 publications spanning a period of not less than ten years since
> then) is a separate matter, not connected to 'nomen dubium' status, but to
> 'nomen oblitum' ('forgotten name') status. A nomen dubium is a
> nomenclatorially valid name whose biological status can't be determined
> satisfactorily; a nomen oblitum is a name that has been overlooked for
> whatever reason, and whose use now would just make everyone confused and
> sulky because it would replace a commonly-used, more familiar name. The
> '50-year rule' was only introduced in the latest (1999) edition of the
> to make recognition of nomina oblita (which are usually fairly obvious)
> automatic and speed up the nomenclatorial process (we don't have to sit
> around waiting for an Opinion before we can get on with our lives).
> Previously, an actual ICZN Opinion was necessary before a name could be
> called a nomen oblitum., and should probably still be called for if
> ever any doubt.
> I'm not sure if this rule would apply in the _Antrodemus_ case, though
> the ideal behind a 'nomen oblitum' is that the name hasn't been used at
> since original publication - i.e. the original publication itself did not
> come to the attention of anyone since. The name _Antrodemus_, while not
> generally used, has probably popped up enough to indicate that people are
> aware of it, just not using it.
> Christopher Taylor