James,
I know the argument advanced by Mathews is of a kind that has been used a lot in ornithology, but the present Code does not allow to reject an available genus-group name based for this type of reason.
What determines the application of a genus-group name is its type species. This type species must be one of the 'originally included nominal species', which are the nominal species included in the genus
and cited by an available species-group name in the original description (see [
Art. 67.2 of the ICZN]). If no included species is cited by an available name in the OD (as is the case here), you are not supposed to try to ID what appears on the plate. You are supposed to look for the first subsequent work where one or more species were expressly included in the genus
and cited by an available name ([
67.2.2]): these will act as the originally-included nominal species, whatever the actual ID of the illustrated bird. If there is only one, it is the type species by subsequent monotypy ([
69.3]); if there is more, the type species needs to be fixed by a subsequent designation of one of the first subsequently included nominal species ([
69.1]). What determines the identity of this type species is the type material associated to the available name by which it is cited; not what appeared on the illustration that made the generic name available.
Cyclopsitta Reichenbach 1850 [
OD] was made available by an accompanying illustration, without any included nominal species. Three year later, Jacquinot & Pucheran 1853 [
here] then combined
Cyclopsitta with the available species-group name
diophthalma Hombron & Jacquinot 1841 [
OD]:
Psittacula diophthalma Hombron & Jacquinot 1841 acts as the only originally included nominal species, and is the type species by subsequent monotypy.
A type species fixed by this method is validly fixed even if it denotes something else than what appeared on the plate. Should the plate demonstrably show another species, your only liberty would be to argue that the type species was misidentified, and to publish an act under [
Art. 70.3], which would allow you to either confirm that the fixed nominal species is the indeed type, even though it is not what appeared on the plate, or to 'correct' the identification by designating 'the taxonomic species actually involved in the misidentification' ([
70.3.2]). Rejecting the type fixation is not an option; neither is rejecting the name as a whole.
Under the present rules, the only way that a genus-group name could ever really be unidentifiable is if a
nomen dubium becomes validly fixed as its type species.
