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




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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