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



--- Guy Leahy <xrciseguy@sbcglobal.net> schrieb:

> Well, there's always this topic:  :-)
> 
>
http://www.sciencemag.org/cgi/reprint/313/5791/1238b.pdf
> 
>
http://www.sciencemag.org/cgi/reprint/sci;313/5791/1238c.pdf
> 
> For those of you that attended SVP, were there any
> new
> papers/talks which shed light on this subject?
> 
> Guy Leahy

Yes, that I would like to know too!

I don't really see a major problem though - Archie was
certainly not a specialized percher, it has been
rather well-supported for long. (I don't think it was
a dedicated ground critter either. Everything seems to
say mainly arboreal, good climber, facultatively
terrestrial).

What would be interesting to know is whether the
hyperextensible TII is really homologous in the
strictest sense, or "just" parallel evolution. What it
proves ATM is that the ancestors of Archie and
deinonychosaurs had a foot morphology sort of
"predestined" to evolve such a structure, but that is
essentially a given in the mainstream hypothesis
anyway.

The third alternative to the "Caudipteryx bird" and
"Caudipteryx non-bird" scenarios (the most celebrated
case as it would be interpreted according to either)
is that the basal exaptations to "birdish" flight -
gliding, downstroke-assisted, four-winged, two-winged,
but in any case utilizing "bird" feathers - was there,
just as the ability to develop a hyperextensible TII
with little evolutionary effort, feathers, the works.

Thus, *true* avian flight (two-winged up/downstroke
with tail used for steering and sone aerodynamical
finery and simple lift, and sternum keel as the main
anchor of flight muscles) might still be
monophyletic/holophyletic. It also is important to
consider that according to how Senter (Acta
Palaeontologica Polonica 51(2): 305&#8211;313; 2006)
reads to me, Archie was not capable of avian flight in
the strict sense (i.e. it could push itself up with
downstrokes, but not fly over long distances because
it could not really raise its arms above its back,
just as in Confuciusornis.

Eike


        

        
                
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