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Re: bauplan convergence



The main problem I have with avian flight originating in trees, is that I can't see a good reason for animals to be leaping from them, unless they had a sort of death wish. Without some form of control mechanism already in place, jumping out of the trees would seem to be detrimental to the population. And, even if some small therapods did spend time in trees, why is it assumed that they must develop flight. Felines have been around for millions of years, and I don't believe there has ever been a flying cat. As far as I can tell, most cats climb down out of the trees instead of taking a 20 foot vertical drop.
Peace,
Rob


From: Betty Cunningham <bettyc@flyinggoat.com>
Reply-To: bettyc@flyinggoat.com
To: dinosaur@usc.edu
Subject: Re: bauplan convergence
Date: Fri, 16 Jun 2000 19:53:24 -0700

#4 -parachuting just doesn't mesh for me as a reason for developing
proto-flapping.

Consider this; a glider wouldn't want to flap as it throws off stability
and control of a glide.  I picture the early aviators pumping away like
mad on their flapping machines as they leap off of cliffs and just
basically plummeting a lot (sure, weight was a major factor then, but
the flapping just didn't aid the plummett one dang bit).

A gliding animal wants fairly immobile wing positions to parachute
with.  A flying animal needs to flap and parachutes both.

An animal that is already flapping to attract females or to scare away
intruders is a prime candidate to have leaping out of trees or leaping
up in the air WHILE FLAPPING and thus accidentally discovering flight,
than a creature that simply leaps out of a tree with the intention of
getting to the ground.

Gravity can get ANYBODY to the ground that leaps out of a tree.

Gravity, air, and a little extra skin on the arms gets you parachuting.

But parachuting doesn't require that you flap.

-Betty Cunningham

Stanley Friesen wrote:
> I didn't say I thought it was viable - it just came closer than most other
> alternatives.
>
> My own preferred *hypothetical* sequence is something like:
> 1. Development of protofeathers for a combination of insulations and
> display. (essentially, self-reinforcing feedback), leading to:
> 2. Enlarged display/brooding feathers on the arms.
> 3. Development of a scansorial/arboreal lifestyle in a small form, allowing:
> 4. Co-option of display feathers as a parachute/proto-wing.
> 5. Elaboration of new function by natural selection for improved aerial
> safety/agility.



-- Flying Goat Graphics http://www.flyinggoat.com (Society of Vertebrate Paleontology member) -------------------------------------------<,D,><

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