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Re: Phytodinosauria status



Hi,

Why?... How...?
I think evolution consists in following tryings, errors and successes.
The loss of 2 digits came long before forelimbs evolve little by little into
wings, I think.
Why did theropods lose 2 digits? Were they useless?
Who knows? But what is important is that those theropods had a good
adaptation to their natural environment.
And when forelimbs evolved into wings, those species like _Archaeopteryx_
where successful because they found their place in the ecosystem.
And when birds lose their digits, it was another successful trying of the
evolution: the wings became longer (cause digits were in it, supporting
feathers) , and birds, better flyers.(and other adaptations became: muscles
and sternum for example, cause of a long natural selection)
And why only forelimbs? I don't know, but it works like that.

Friendly,
                   Luc J. "Aspidel" BAILLY aspidel@infonie.be

p.s.: excuse my poor English.

----- Original Message -----
From: <Dinogeorge@aol.com>
To: <dinosaur@usc.edu>
Sent: Thursday, June 07, 2001 9:39 PM
Subject: Re: Phytodinosauria status


> In a message dated 6/7/01 1:59:01 PM EST, david.marjanovic@gmx.at writes:
>
> << Here you IMHO run into the same problems as Feduccia -- why should the
>  forelimbs (and only they) evolve into wings in a quadruped, and why
should
>  they lose digits in an arboreal animal??? >>
>
> They can easily evolve into wings in a leaping quadrupedal arboreal
animal,
> since they are no longer entirely involved in physically supporting the
> animal but have become involved in aerodynamic control (along with the
tail)
> during the leap phase and in helping the animal to alight at the end of a
> leap (furcula is the shock absorber for this). Digits were lost from the
> outside in because these digits in particular ruined the aerodynamics of
the
> feathered wing.

(OK but not only, see higher)- LJB.

> The feathers were there long before the wing, of course, and
> the wing itself goes back to before Herrerasaurus, which already shows
strong
> reduction of manual digit V. Evolution of the wing is the reason manual
> digits IV and V are reduced/lost in all post-sauropod dinosaurs.

What reason?? - LJB
>
> The hind limbs were still needed when the animals were grounded; a running
> start, for example, might have been the way they took off from the ground
> when the wings were still unable to provide all the energy for that job
> themselves.
>
> The problem I have with the usual scenario is there is simply no way the
> small, grasping forelimbs of a Coelophysis-size theropod could have
evolved
> into wings. What possible aerial function would such pre-wings of a
running
> theropod have? (Or are you one of those who imagines that the wings of
birds
> evolved all their aerial features on the ground, and then as if by magic
the
> animals were suddenly able to fly, never having previously touched the air
> with wings?)

Sure not, see for example _Microraptor_ and _Archaeopteryx_ - LJB

> Feathered pre-wings would get in the way of any predatory
> grasping function but provide no compensating payoff. And just because >I<
> may be too stupid to think of such a payoff is not an argument >for< such
a
> payoff, either. Nobody else can come up with one, either.