RE: Sereno's (2005) new definitions

[Michael Mortimer <mickey_mortimer111@msn.com>]

Tim Williams wrote-

> > A nomen dubium cannot influence a topology except to create a polytomy 
> > which covers its potential placements.  Only taxa with unique combinations 
> > of characters can influence topologies, but nomina dubia by definition 
> > lack those.
>
> Depends who you ask.  :-)  I would say that a unique combination of 
> characters is enough to uphold the validity of a taxon - and I'm sure you 
> would too.  But there is another (more stringent) view that a taxon must 
> have autapomorphies in order to be deemed valid.  That seems a little harsh 
> to me.

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.

> > > In other words, we could put a nomen dubium into a matrix - but why would 
> > > we need to?  Why, when we could just replace the nomen dubium with an 
> > > unquestionably valid taxon?
> >
> > To tell what the nomen dubium's phylogenetic relationships are, of course.
>
> But by definition, a nomen dubium does not represent a discrete organism.  
> Because a nomen dubium has no unique characters (or combination of 
> characters) it cannot be differentiated from other taxa.   For example, 
> _Antrodemus_ might be _Allosaurus_, or it may not be; we're never going to 
> know.  Therefore it is weird (for want of a better word) to include a nomen 
> dubium in a matrix.  I think this is what Jaime is also driving at: a nomen 
> dubium has nomenclatural standing (in the sense that the name is valid) but 
> no taxonomic standing (in the sense that we don't know what organism it 
> pertains too).

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

> > Why view -idae and -ia clades differently if we're ignoring the ICZN?
>
> Because -idae clades should at least be assured of containing the eponymous 
> genus.  This goes way beyond the ICZN: the suffix -idae represents a 
> tradition going back thousands of years.  The ancient Greeks used '-idae' 
> to designate a dynastic lineage or family: Atreidae, Heraclidae, 
> Achaemenidae, Seleucidae, Arsacidae, etc.  Each lineage/family had the 
> eponymous ruler or hero as a member - in these cases, this was the founder 
> (real or alleged).  So, to answer your question, -idae and -ia should be 
> viewed differently because -idae actually denotes something in its own 
> right.

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.

Mickey Mortimer