RE: Sereno's (2005) new definitions

[Tim Williams <twilliams_alpha@hotmail.com>]

Mickey Mortimer wrote:

> True enough, though I don't see how a metataxon (organism without known 
> autapomorphies) would be a negative influence on a topology, as it is still 
> an organism with some phylogenetic relationship to other organisms.

Yes, I agree.

> A nomen dubium does represent a discrete organism.  The Antrodemus holotype 
> partial caudal centrum was part of a discrete organism back in the 
> Jurassic.

In this context I meant a nomen dubium cannot represent a discrete taxon.  
The _Antrodemus_ holotype partial caudal centrum did come from an organism, 
but the genus or species identity of that organism is indeterminate.  Thus, 
for the purposes of taxonomy, _Antrodemus_ is a non-entity.

> This individual may have been congeneric (whatever that means) with what we 
> call Allosaurus or not.  Do you mean it's weird to include an OTU that may 
> be synonymous with another OTU?  So you'd have problems with an analysis 
> including both Citipati AND IGM 100/42 (the so-called Citipati sp. which 
> represented Oviraptor in the last few decades), because the IGM 100/42 
> specimen might be Citipati?  Or with Caenagnathidae AND Elmisaurus rarus, 
> because the latter could be inside the former?

No, I have no problem at all with possible synonyms being included in the 
same analysis.  After all, we are never going to *know* with a 100% 
certainty where the boundaries for each species or genus lies.  The best we 
can do is erect a diagnosis for each species and genus, and see if the 
diagnosis holds up in the light of new or revised data.

My objection to nomina dubia being used in analyses is more philosophical.  
A nomen dubium (= nomen vanum) means that the name is removed from taxonomy. 
 And given that taxonomy is predicated on phylogeny, nomina dubia should be 
excluded from analyses.

The other issue with potential synonyms (e.g., Caenagnathidae and 
_Elmisaurus_) is that there is a theoretical and philosophical possibility 
that the question of synonymy will be resolved.  We may indeed find a 
specimen that indicates whether _Elmisaurus rarus_ is referrable to the 
Caenagnathidae, and until that occurs there is no problem upholding both as 
valid taxa (OTUs).  With nomina dubia, by contrast, the identity of the 
taxon is indeterminate, and will remain so.  As I said, we are never going 
to know what genus or species _Antrodemus_ represents, because the name is 
forever limited to the type specimen.  A nomen dubium is a nomenclatural 
dead-end.

> Meh, linguistic reasons don't rate highly in my book, especially since this 
> isn't even implied by the suffix itself, but rather with historical details 
> of how the suffix was used when applied to a different concept. But I'm the 
> guy who could care less if names are formed correctly from Greek and/or 
> Latin, so maybe my apathy isn't representative of the paleo community.

*gasp*

:-)

I guess I'm more of a purist.  Although I'm no fan of Linnaean hierarchies, 
I think we can do better when it comes to forming new names.  For example, 
is it so difficult to figure out that the family-level name based on 
_Caudipteryx_ is 'Caudipterygidae' and not 'Caudipteridae'?  It doesn't take 
much time to determine what the correct form of a name should be; and to not 
do so comes across (to me, anyway) as sloppy.  I wince every time I see 
'Caudipteridae'.

Cheers

Tim