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Re: 11th specimen of Archaeopteryx

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.


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?