But fails to become the current name because it was unused for 30 years after publication so is a Nomen oblitum?
No, "that" rule said 50 years, not 30, and it fell out of use in 1973. See
Article 23.9 of the Code for the current flavour.
Basically:
- No name ever "is a
Nomen oblitum" automatically; you need a published nomenclatural act that makes it one.
- The current rule works with a fixed reference date, not with a moving time window. (It was feared that in less-studied groups, some authors might want to "wait" the end of the time period, so that names became forgotten, and might be displaced by newly proposed names.) The fixed date is end of 1899/begin of 1900. You'd need to make sure that Arremonidae, -inae, -ini, -ina, or -whatever, was not used as valid in
any publication since that date, whichever the rank. (It may be that it wasn't. The name was in use in the mid-1880's; it certainly appears in some post-1900 publications, but up to now I've only found it in descriptions of pre-1900 classifications which are not adopted by the authors, and this would not count. Unfortunately, the 20th C literature is now much less easily accessible than older works, hence it's easy to miss things; also, finding family-group name with search engines doesn't work very well in my experience, in part because OCR programs often have a hard time with final -æ's. If you want to find everything, you really ought to check everything. Note that
TiF uses Arremonini right now for a tribe -- but of course TiF is not published, so this doesn't count.)
- A name can't be made a
nomen oblitum unless it threatens a junior name, that must be demonstrably widely established. Here, the "widely established" threatened name would be Passerellidae: you'd need to find at least 25
published works that used this name as valid, by at least 10 different authors, published within the last 50 years (thus no early 20th C literature), and spanning at least 10 years (thus some of them would have to be from before the group started to be recognised as distinct from Old World Emberizidae in the "modern times"). You can try, but I doubt this can be done.