Re: 11th specimen of Archaeopteryx

[Don Ohmes <d_ohmes@yahoo.com>]

On 11/2/2011 12:40 AM, Scott Hartman wrote:

> It may not be necessary to have all of these adaptations, but
> Archaeopteryx doesn't have_any_  of them.  The foot is simply the
> opposite of what we would expect of a bird-like animal that lived in
> trees.  In the absence of any other supporting data it's just special
> pleading to keep trying to explain away the foot anatomy as somehow
> "not preventing" an arboreal lifestyle.

Swzadzadzxadzxdxdzxdzxdzxdzx!!!!

I have not assigned Archie an arboreal lifestyle. A ground-foraging 
tree-roosting lifestyle (GFTR) is not in any meaningful way "arboreal", 
nor would it result in "arboreal adaptations" -- this is because the 
critical tasks (food and nesting) occur on the ground, and contra Tim, 
sleeping in a tree just ain't that hard to do.

Nor is my central point Archie-specific -- assuming limited upstroke in 
bird ancestors severely weakens the plausibility of "active" scenarios 
culminating in flapping flight, no matter what animals you designate as 
bird-ancestors, and no matter what wing-creating scenario you prefer.

By exclusion, "passive" scenarios become more plausible -- and 
Archie-*type* animals were entirely capable of accessing potential 
energy on a daily basis, simply by roosting nightly.

As a corollary, I ask "What other scenarios are there (for accessing 
potential energy)?"

Obviously, Archie and ancestors/siblings were not arboreal creatures, so 
the classic trees-down arboreal lifestyle is excluded...

The special pleading occurs when people insist that the simple act of 
sleeping in a tree inevitably results in measurable skeletal changes in 
an animal already physically capable of climbing, but fully optimized to 
a cursorial lifestyle. It might, or it might not...

That descendants of at least some members of the functional clade 
"Archie-type" eventually evolved the traits you list certainly does not 
imply that Archie-types spent no time whatsoever in trees -- some of 
them must have -- how else would they have eventually acquired such 
specialized feet?

To reason that all animals w/out such adaptations necessarily spent no 
time in trees is circular from the evolutionary perspective -- albeit 
prudent when considering individual taxa.

The relevance of GTFR hinges on the physical reality of limited upstroke 
in archie + ancestors + siblings -- and that is where I hoped this 
discussion would wander to eventually.

Is "limited upstroke" fact, or opinion?