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RE: Greg Paul's new (or newly named) iguanodonts



Tom Holtz wrote:

> The original work of Gauthier, Clark & Benton, Parrish, & colleagues back in
> the 1980s was really to sort out this mess, and resolve that classic
> archosaurs fell into three clusters: dinosaurs, pterosaurs, and their kin;
> primitive guys (the traditional "proterosuchians" as well as Euparkeria and
> Proterochampsidae); and the croc-ankle cluster.

There was a fourth category (not so much a 'cluster'), which might  be called 
"WTF".  Things like _Longisquama_ and _Sharovipteryx_ (_Podopteryx_) ended up 
here.  :-)

> And really: those who have argued for a "thecodont" origin since the 1970s
> (Tarsitano, Martin, etc.) argued for relationships with animals that
> thecodont workers (Charig, Parrish, Chatterjee) would not consider
> thecodonts at all!! 

Except for maybe _Scleromochlus_ (which has popped up as a 
prospective'pro-avian' once or twice).  But yes, I know exactly what you mean.  
The thing is, if we revive Thecodontia as a paraphyletic taxon, we also revive 
the "blob" (as David puts it).  These 'blobby' paraphyletic groups were 
conveniently used as the ancestral stock for more 'advanced' groups, by way of 
a stippled line (or even a finger-like protuberance, if we were really 
confident).  Thecodont to bird, condylarth to ungulate, and so on.  But by 
naming paraphyletic taxa simply to make classification 'easier' (or at least 
more aesthetically pleasing) we risk resurrecting not only disused names, but 
also the outdated concept behind the name.  That's my concern.  Even if a 
'new-and-improved' Thecodontia had an explicitly defined content (under PN), 
and not just be a 'blob', doesn't change the fact that the name would probably 
be misused.  Those who have argued for a "thecodont" origin since the 1970s 
would ignore the
 content of a rigorously defined (although still paraphyletic) "Thecodontia" 
and simply focus on the fact that the name itself is now back in play, and 
manipulated it for their own ends.  (Cue maniacal laughter in the background.)

> (This is opposed to the Heilmann model, which did derive
> birds out of Euparkeria-like forms).

I think he might have put _Ornithosuchus_ there too.  Not 100% sure though.

Cheers

Tim


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