RE: Avian Monophyly (Was Re: Sheesh)... :-)

[Tim Williams <twilliams_alpha@hotmail.com>]

Evelyn Sobielski wrote:

> To which might be replied that Neornithes is monophyletic by definition, 
> but ratite phylogeny is
> still too badly understood to say exactly how deep the paleognath-neognath 
> split is.

I may have my wires crossed here, but I was making the point that the only 
birds (avians) *known* to have survived the end-K extinction belong to the 
Neornithes.  This is true irrespective of how deep the palaeognath-neognath 
split is.

> Supposing the paleognath-neognath split goes back to c. 100 mya (or even 
> deeper?), then Neornithes becomes a rather arbitrary assemblage united more 
> by C-T survivorship than by a
> robust cladistic model.

If Neornithes is monophyletic (and, as you say, it must be) then it cannot 
be an "arbitrary assemblage".  I'm confused here.

> What they apparently did was to outcompete the transitional paravian flyers 
> in the Early Cretaceous (although the Enantiornithes certainly had a larger 
> share in that),

I don't think we have enough evidence for such a detailed scenario regarding 
Enantiornithes vs Euornithes.  AFAIK, neornithean birds do not appear in the 
fossil record until the Late Cretaceous.

> 4-winged Microraptor had no problem competing with the advanced "true" 
> avian flyers it appears.

I don't think microraptorans actually competed with birds, any more than 
flying squirrels compete with bats nowadays.  In this context, 'coexisting' 
is probably a better term than 'competing'.

> And Archie wouldn't have needed to perch: it had hands. Not fully 
> functional, but still hands
> with discrete fingers.

I tend to agree.  Ditto for microraptorans, and probably 
(as-yet-undiscovered) basal paravians.

> Even pygostyles now appear not to be synapomorphic (i.e. evolving only 
> once).

There is some question over whether the stumpy coossified tail of certain 
oviraptoriforms (_Nomingia_, _Beipiaosaurus_) should actually be termed a 
true 'pygostyle'.

> The main problem with that would be competition. It was not the best of 
> runners.

What would _Archaeopteryx_ be running from?  It lived on a bunch of islands. 
 In any case, its cursorial adaptations were about on par with dromaeosaurs 
or basal coelurosaurs.

> I like a scenario as outlined by Elzanowski in "Mesozoic Birds": Archie 
> using its wings to gain successively higher perches,

Doesn't this require perching ability?

Cheers

Tim

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