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RE: Greg Paul is right (again); or "Archie's not a birdy"



  Note that *Protarchaeopteryx robusta* is almost certainly one of the most 
basal oviraptorosaurs, and was more basal than *Caudipteryx zoui*. With this in 
mind, note that the arms in *robusta* are longer than in *zoui*, and retain a 
developed third manual digit. Moreover, the jaw is more extensively and 
robustly toothed, and the tail somewhat longer. While this shows a trend down 
to a reduction in limb design, it implies the basal condition was the same for, 
say, troodontids in overall _bauplan_ (minus the super-long tail). Even the 
pelvis was similar in structure, although the pectoral girdle appears to differ 
distinctly (the coracoid is not rotated ventrally, and the sternum is extremely 
anteroposteriorly short and broader than long). This creates a strong 
distinction with taxa like *Anchiornis huxleyi* and *Mei long* at least.

  I'm not saying you're wrong, but the jaw and limb anatomy also imply a 
potentially less predatory advantage and I wonder at the constraint towards 
arboreality without a ecological constraint on that manner. We see 
eco-partitioning among similar taxa in varanids and monkeys, and for the most 
part, there are high-canopy, low-canopy, and near-ground taxa, and I suspect 
basal oviraptorosaurs (so far as we know them) are terrestrial taxa with some 
chukar-like scansorial habits. I do not see them as four-limb grapple-climbers, 
although I do not discount the possibility.

Cheers,

  Jaime A. Headden
  The Bite Stuff (site v2)
  http://qilong.wordpress.com/

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


"Ever since man first left his cave and met a stranger with a
different language and a new way of looking at things, the human race
has had a dream: to kill him, so we don't have to learn his language or
his new way of looking at things." --- Zapp Brannigan (Beast With a Billion 
Backs)


----------------------------------------
> Date: Fri, 29 Jul 2011 11:31:35 +1000
> From: tijawi@gmail.com
> To: dinosaur@usc.edu
> Subject: Re: Greg Paul is right (again); or "Archie's not a birdy"
>
> Jason Brougham <jaseb@amnh.org> wrote:
>
> > My point is precisely as you have suggested: Xu's new topology leaves it 
> > unclear whether the last common ancestor between Archaeopteryx and birds 
> > was volant or engaged in any aerodynamic
> > behaviors at all.
>
>
> Pennaceous remiges and/or rectrices are present in non-paravians such
> as _Caudipteryx_, _Similicaudipteryx_, and _Protarchaeopteryx_. The
> presence of what has been called a 'pennibrachium' by Sullivan et al.
> (2010) (a forelimb bearing long feathers that form a planar, wing-like
> surface) is primitive for a more inclusive clade than Paraves. As
> Sullivan &c point out, these pennibrachia might originally have had no
> function at all in aerial locomotion - although by Paraves (at the
> latest) it is almost certain that pennibrachia (wings) were used for
> some form of aerial locomotion. That means that if _Epidexipteryx_ is
> an avialan, its lack of pennibrachia is secondary, although the
> forelimbs were not truncated. Curiously, _Caudipteryx_ had short
> forelimbs (by maniraptoriform standards), but retained pennibrachia.
>
>
> Whether the last common ancestor of _Archaeopteryx_ and birds was
> volant (or engaged in any aerodynamic behaviors at all) depends on if
> pennibrachia evolved for some form of aerial behavior. I suspect that
> they did. As the ancestors of birds were likely herbivores, I picture
> them scaling the trunks of cycads, plucking the nutritious seed cones
> at the apex, then using gliding to return to the ground safely. I've
> probably mentioned this before, so apologies for any repetition.
>
>
> > When you suggested that Epidexipteryx looks secondarily flightless I wanted 
> > to point out that it could look primitively flightless as well, given a 
> > different hypothesis.
>
>
> _Caudipteryx_ has been the subject of a similar debate. I side with
> the view that its ancestors were gliders, but that _Caudipteryx_
> itself had lost any aerial abilities.
>
>
>
>
>
> Cheers
>
> Tim