ME:
I was trying to not get carried away on the details...

Ok first up I agree with most of what you said and reading what I said I used an incorrect term in saying "conspecific" at one stage.

All we looked at was the availablity of the name, we did not analyse wether the group of species it refers to (also known as the Chelodina B group) warrants generic recognition. That said we took the view that the original description of Macrochelodina claimed that this was a genus in its own right. There has been no evidence presented that suggests otherwise though in saying that the issue was not directly tested. Hence if the name applied to a valid group that was unnamed and did not fail any other tests you mention then it was the oldest available name for that taxon.

The original type species of Macrochelodina was M. oblonga. This caused serious issues for two reasons. First up because this species is a member of the Chelodina A, and second because the name C. oblonga has been incorrectly applied.

Thomson 2000, showed that the holotype of C. oblonga was in fact a C. rugosa and that the valid name for the Western Australian species is Chelodina colliei. However I took the stand in that paper to maintain the status quo awaiting a decision by the ICZN on the issue. We cannot right it off as Nomen oblitum or something because the name C. oblonga was correctly applied till 1974.

That is well and good for Chelodina oblonga (=colliei) but the effect on Macrochelodina is different. Types are conserved in nomenclature hence the type species of the genus is that taxon to which the holotype belongs, ie Chelodina rugosa. All these corrections were made in the paper.

So the conclusion was that the name Macrochelodina was the available name for the Chelodina "B" (or Chelodina expansa group) and was the oldest available name for the genus.

Wether it should have been recognised is another matter. There has been considerable evidence published that demonstrates a completely different bauplan for the Chelodina and the Macrochelodina. I use the name now bexause I feel it has been described and I use the view of "refute or accept", despite describing two species in this group and assigning another I have no evidence that can refute this as a genus. As the members of each genus have a different bauplan, they both form monophyletic groups (I know you hate that one) and there is a "decided gap" between them that is more extensiive than that between any short neck genus. Though I recoignise that genera do not have to be equal.

CKing:
"Chelodina and "Macrochelodina" are higher taxa. Higher taxa are entirely categories of artificial human construct. There is no universally accepted definition for any higher taxa, although it has been customary to define animal phyla on the basis of their different body plans. Different biologists may recognize different numbers of kingdoms for example. Hence it is possible that some people will recognize two or more higher taxa (including genera) while others may only recognize one. Such disagreements are entirely philosophical and subjective. Hence there is no way to "prove" whether two species belong in the same higher taxon or not. Therefore there is nothing that could compel anyone to recognize "Macrochelodina." Further, even if the genus Chelodina were to be split, the name "Macrochelodina" may or may not be used. For example, if the type species of "Macrochelondina" should be considered a member of Chelodina, then the name becomes a junion synonym. In that case, another name may need to be applied to the other genus or genera resulting from the split. Whether "Macrochelodina" is a valid taxon or not is therefore, as Scott Thomson had stated earlier in his post, a different issue than whether the name is valid or not."

Cheers, Scott
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Scott Thomson

http://www.carettochelys.com
http://ittn.net

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