And since I see that's already been pointed out a minute earlier, I'll add that the supplement acknowledges that Arremonidae has priority over Passerellidae, but argues that Arremonidae is a nomen oblitum.
"a
nomen oblitum under Articles 23.9 and 35.5"...
First
35.5:
35.5. Precedence for names in use at higher rank. If after 1999 a name in use for a family-group taxon (e.g. for a subfamily) is found to be older than a name in prevailing usage for a taxon at higher rank in the same family-group taxon (e.g. for the family within which the older name is the name of a subfamily) the older name is not to displace the younger name.
This is an article that protects the widely and long-accepted relative precedence among names
that are in use. This is 100% irrelevant to the present case, because Arremonidae is not in use for a taxon below the family rank within Passerellidae.
Then
23.9 (I have removed the example and recommendation, these are not part of the legal text anyway):
23.9. Reversal of precedence. In accordance with the purpose of the Principle of Priority [Art. 23.2], its application is moderated as follows:
23.9.1. prevailing usage must be maintained when the following conditions are both met:
23.9.1.1. the senior synonym or homonym has not been used as a valid name after 1899, and
23.9.1.2. 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 23.9.1.2 are met, and also state that, to his or her knowledge, the condition in Article 23.9.1.1 applies. From the date of publication of that act the younger name has precedence over the older name. When cited, the younger but valid name may be qualified by the term
nomen protectum and the invalid, but older, name by the term
nomen oblitum (see Glossary). In the case of subjective synonymy, whenever the names are not regarded as synonyms the older name may be used as valid.
[...]
23.9.6. The deliberate use of a name contrary to Article 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 determining usage under Articles 23.9.1.1 and 23.9.1.2.
No name
ever becomes a
nomen oblitum "on its own" under the current Code, even when it has not been used for centuries; a name can only be a
nomen oblitum relative to a nomen protectum, which must have been in very wide use for a significant time. (And, even when it is a
nomen oblitum, a name can still re-enter usage as long as it does not displace its
nomen protectum.)
Before Arremonidae can be called a
nomen oblitum, the Committee (or somebody else)
should have published evidence that Passerellidae (the wannabe
nomen protectum) has been used as a 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. From the date of publication of that evidence, Passerellidae might justifiably claim precedence over Arremonidae.
Hint: Passerellidae was reintroduced into usage by Barker et al 2013 [
here]. We are now in 2017.
Of course, Bock 1994 does not count because, even though he cited Passerellidae, he did not use the name as valid.
(I have seen a Commissioner arguing that 23.9.6 makes any use of the name post-1999 not it be taken into account in determining usage under Articles 23.9.1.1 and 23.9.1.2, in which case Arremoninae could
never become a
nomen oblitum, because Passerellidae has been used exactly zero times in the last 50 years and before 2000, and anything more recent doesn't count. I don't agree with this reading, though. The present use of Passerellidae by the Committee, however, should obviously not be taken into account.)