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Re: Nomina Dubia Part II: Rapator



Tim Williams wrote:

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 When we split or lump genera, nothing is being tested.  Nevertheless,
 we are still doing science.

No, nomenclature.

 For example, if somebody finds that _Hesperosaurus_ and _Stegosaurus_
 are sister taxa, and consequently decides to lump them in the same
 genus, they must first build a case using the available evidence for
 regarding _Hesperosaurus_ as a species of _Stegosaurus_.

Not under the rank-based codes.

Remember, "genus" is not defined. There isn't even a way to build a case. The ICZN gives you the right to _simply claim_ they're the same genus; as long as you're following the ICZN in all other respects (such as providing a diagnosis for the new & improved *Stegosaurus* -- such a diagnosis does not need to be anywhere near correct, BTW), this is a valid nomenclatural act.

And then everyone (yourself included) has the right to call you full of shit and separate the two genera again, for any or no reason.

And both opinions are equally valid forever as far as the ICZN is concerned.

If you believe that genera should be synonymised if they taxa they used to describe are sister-groups, and if (...whatever...) the morphological diversity in the whole clade is below whatever limit you wish to define or not define _or_ keeping them separate would make the classification unmanageable _or_ whatever, and if you _then_ make a case that *H.* and *S.* fulfill _those_ criteria, that's fine, but you're satisfying yourself here, not the ICZN. The ICZN couldn't care less.

Phylogenetics is science. Nomenclature is not, it's a set of arbitrary conventions.

 So although it's not testable (because ultimately it is a subjective
 decision), I would still regard it as 'doing science'.

It's not "ultimately", it's a subjective decision from start to finish, because "genus" isn't defined, and "*Hesperosaurus*" and "*Stegosaurus*" are incompletely defined ("whatever genus contains *H. mjosi*", "whatever genus contains *S. armatus*"). All, literally all, the ICZN does is tell you which names to sink if you declare them synonyms. It does _not_ say _anything_ about which reasons you might have for declaring anything synonymous. You're in all seriousness allowed to do as you please.

Scary, I know. But that's what rank-based nomenclature is like.

> As soon as you can't answer the question "if I were wrong, how
> would I know?" any longer, you're not doing science.

 That's a little harsh.  Some scientific questions have no "right" or
 "wrong" answer.  Is _Brontosaurus_ the same as _Apatosaurus_?  The
 evidence suggests "yes";

The evidence can't suggest anything, because "genus" is not defined. OK, science can in principle tell us (even if only by parsimony arguments) if *B. excelsus* and *A. ajax* are, say, different growth stages or different sexes or individual variation of the same... the same... the same LITU, but that basically is it. If they're separate species by whatever species concept you might prefer*, there is no way evidence could suggest or not suggest they're the same genus.

Unless you define "genus" first. Again, the ICZN has never even tried to do that.

* It goes without saying that the ICZN doesn't say anything about species concepts and couldn't care less.

 but we're never going to KNOW for certain.

If you want to go down that road... we can't know anything for certain. It's not even possible to disprove solipsism.

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Mike Keesey wrote:

 what is science, if not a body of knowledge gleaned from tests?

The methods of testing themselves... science is something you do, an activity, not a collection of facts.