Laurent, what do you mean in saying that Pandion leucocephalus is available? You do not suggest that the osprey from Britain should be renamed this?
I think you are confusing two notions - availability and validity.
Nomenclatural availability simply means that a name has been introduced in a "correct" way - it must have been published (in the sense of the Code), in a work applying binomial nomenclature consistently, must be written using the Latin alphabet, must have been accompanied by a description or an indication, and so on... (The requirements are covered by Chapter 4 of the ICZN; there are more and stricter requirements for recent names, but less and more loosy ones for older names.)
If a name is available, it just "enters the arena" of nomenclature.
The "valid name" of a taxon is the name that correctly applies to it according to the rules of nomenclature. This name is always
one of the available names that demonstrably apply to the taxon -- usually the oldest one, except if this one is invalidated for some other reason (e.g., because it is a junior homonym of a name that applies to another taxon).
If
Pandion leucocephalus "N.F." is available, it is:
- A junior synonym of
Falco Haliaetus Linnaeus, 1758. But the latter has priority, thus is and must remain the valid name of Eurasian ospreys.
- A senior primary homonym of
Pandion leucocephalus Gould, 1840. "Primary homonym" means that not only the species-group names have the same spelling, but they also were originally proposed in combination with the same genus-group name. A junior primary homonym can normally not become a valid name - thus, the existence of an available senior homonym should imply that
Pandion leucocephalus Gould cannot become the valid name of Australian ospreys.
(There is a "but", here, though...
Article 23.9 of the present Code allows for a reversal of precedence when it is discovered that a name
that is in prevailing usage has an old senior homonym that nobody is using anymore. Two conditions must be met (Art. 23.9.1):
- the senior homonym must not have been used as a valid name after 1899, and
- the junior homonym must have 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.
The first condition is more than likely met in the present case. But the second is probably more problematic, because most authors have been using
cristatus (Vieillot) -- and therefore not
leucocephalus Gould -- as the valid name of this taxon over the last 50 years. If this second condition happened to be met as well, then
leucocephalus "N.F." should be declared a
nomen oblitum (a forgotten name), and
leucocephalus Gould a
nomen protectum (a protected name). If so, continuing to use the latter would be OK.)
The next valid name for the Australian Osprey, I meant. I now think it is P. gouldii, I should have read "Order names" first. Pandion gouldii Kaup Isis 1847 p. 270
(You mean the next
available name.)
Pandion gouldii Johann Jakob Kaup, 1847. Monographien der Genera der Falconidae.
Isis (Oken), Jahrgang 1847 (IV): 270.
(New name for
Pandion leucocephalus Gould, "der australische Milanaar", offered "Da wir bereits einen
Haliaëtus leucocephalus haben" [because we already have a
Haliaëtus leucocephalus].)
Full text here:
http://www.archive.org/details/isisvonoken1847oken
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