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

[Tim Williams <twilliams_alpha@hotmail.com>]

Evelyn Sobielski wrote:

> I don't really see a major problem though - Archie was certainly not a 
> specialized percher, it has >been rather well-supported for long.

Yes, true.  I would even go a little further and say that Archie couldn't 
perch at all.  That's not to say that it wasn't arboreal, though.

I think this alleged non-monophyly of Aves is a storm in a teacup.  The 
Science paper by Mayr et al. (2005) implies that the monophyly of Aves is 
challenged if _Confuciusornis_ is shown to be closer to traditional 
non-avian taxa (like dromaeosaurids) than to _Archaeopteryx_.  But Aves, by 
definition, is monophyletic.  All that happens under the proposed cladogram 
is that some additional taxa (dromaeosaurids & troodontids) get scooped up 
into Aves, which in turn suggests that secondary loss of flight occurred in 
certain taxa close to the base of the Aves.

A future analysis may recover a different topology, such as an 'orthodox' 
_Archaeopteryx_-_Rahonavis_-_Confuciusornis_ clade that excludes 
deinonychosaurs.  As has been noted previously, non-basal avians are 
conspicuous by their absence from Mayr &c's analysis, and this is sure to 
have an effect on the result.

> (I don't think it was a dedicated ground critter either. Everything seems 
> to say mainly arboreal, good climber, facultatively terrestrial).

I'd say Archie was facultatively arboreal and mainly terrestrial.  Of 
course, in terms of the requisite adaptations, this may be a distinction 
without a difference.  :-)

> 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.

I don't know if I'm understanding you correctly (so apologies in advance) 
but my 'take' on _Caudipteryx_ is that its 'advanced' bird-like plumage is 
the product of an ancestry from among gliding (or parachuting) 
maniraptorans, and that _Caudipteryx_ itself spent all of its time on the 
ground and did not glide.

Cheers

Tim

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