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Re: Campbell's even crazier than a MANIAC? (archeopteryx climbing)



> Humans possess pronating and supinating wrists, a highly
> mobile shoulder joint that can rotate the arm about its axis
> with a nearly 160 degree range of movement in three
> dimensions, and they can, to some degree, supinate the
> ankle.

no doubt we have climbing adaptations, but we lost others such as a prehensile 
foot and a prehensile tail. This point was in response to the statement made 
earlier:

> Archaeopteryx not only lacks those adaptations, but the phenotypic 
> trend of maniraptorans is to do the exact opposite 

My point is a trend away from an ability, does not mean that ability is no 
longer used.

What is WAIR?

I'm not saying archie climbed trees, especially not like a squirrel - just that 
the absense of the adaptations mentioned may not be relevant.
Furthermore, if archie or some hypothetical ancestor of archie did climb up 
something to glide, it wasn't neccesarily a tree, as I mentioned boulders and 
cliffs.

> The problem lies in several elements,
> including the apparent "half of a wing". What use
> is such a structure on the evolution towards flight?

Is holding its arms outstretched, and rapidly parting them to suck in a flying 
insect even plausible?
We know of many examples of feeding by sucking in the fluid surrounding prey, 
when the fluid is water - a fish merely need open its mouth.

Why can't a similar method work with air? it would give "half a wing" some use, 
and could then easily become a gliding surface.


--- On Thu, 9/4/08, Jaime A. Headden <qilongia@yahoo.com> wrote:

> From: Jaime A. Headden <qilongia@yahoo.com>
> Subject: Re: Campbell's even crazier than a MANIAC? (archeopteryx climbing)
> To: erikboehm07@yahoo.com
> Cc: dinosaur@usc.edu
> Date: Thursday, September 4, 2008, 2:05 PM
> Erik Boehm wrote:
> 
> <I think the perching adaptation that birds have is only
> of use once a minimum proficiency in precision flight is
> attained, and for the first examples of therepod flight, the
> absence of a reversed toe for perching probably is
> irrelevant in the arboreal vs cursorial debate.>
> 
> The problem here is that *Archaeopteryx* doesn't appear
> to even be that important of a player on the direction
> toward birdiness. The problem lies in several elements,
> including the apparent "half of a wing". What use
> is such a structure on the evolution towards flight? There
> is no actual direction just as there is not actual
> destination, so what features we peg as "towards
> flight" have to operate under a paradigm while the
> animal was alive. WAIR can help explain this, but it
> doesn't answer everything.
> 
> Your argument is still flawed in what you are using to
> analogize your climbing *Archaeopteryx*:
> 
> <However, humans still regularly climb trees(some more
> than others depending on where one is), despite an
> evolutionary trend away from adaptations to do so. It does
> coincide with a dramatically decreased need or reason to
> climb trees however.>
> 
> Humans possess pronating and supinating wrists, a highly
> mobile shoulder joint that can rotate the arm about its axis
> with a nearly 160 degree range of movement in three
> dimensions, and they can, to some degree, supinate the
> ankle. They also, like Scott mentioned with squirrels, climb
> close to the substrate and now out and away from it on less
> flexible levers that are the legs and arms.
> 
> *Archaeopteryx*' legs and hips were so incapable of
> this modus that it is unlikely they were in any aspect
> arboreal. This doesn't mean they couldn't climb, but
> they certainly weren't arboreal or even scansorial in
> this perspective. The ankle and leg suggest, rather, a more
> terrestrial modus for the legs, with a combination of
> digital proportions and claw curvature that implies some
> ability to grip a substrate, which Yalden and Feduccia both
> have linked to some scansorial possibilities, although the
> latter makes more of this than the former. This can be used
> also as an argument for climbing _prey_, although not much
> bigger than crocodylians appear in the Solnhofen beds.
> 
> <IF birds evolved from the trees down - as flight got
> better, I would expect to see tree climbing abilities
> getting worse, as flight would become the prefered method of
> getting up (can any bird "climb" a tree now? the
> most I see is gripping on the side of a trunck one and
> moving a few inches inbetween flight) Was archie even close
> to being a good enough flyer that it could sacrafice any
> (hypothetical) ancestral climbing abilities? (probably
> not)>
> 
> This seems odd, because many living bird groups,
> significant among them but not limited to them being Pici
> (aka, the woodpeckers) are exceptional as being arboreal,
> and can even walk up vertical surfaces. Others, including
> parrots and colies, take agility while on a branch to
> extremes rivaling much of the rest of the avian tree; and
> all are prodigious and capable fliers. It's when a modus
> becomes enforced that adaptation to other modi becomes
> reduced: Living on the sea or under it does not require the
> ability to fly through the air, so several lineages have
> lost flight as a consequence of adapting to this, including
> cormorants, auks, and penguins. Note that they didn't
> lose flight TO adapt; these birds still use their flight
> apparatus underwater, but can no longer fly in the air (with
> the exception of some auk relatives and clumsily for some
> cormorants).
> 
>   Cheers,
> 
> Jaime A. Headden
> http://bitestuff.blogspot.com/
> 
> "Innocent, unbiased observation is a myth." ---
> P.B. Medawar (1969)