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Re: tiny theropod on a tree trunk question



PTN-- "Elongation of the distal arm feathers and rotation of the hand would 
have been highly selected for among fast (flightless) cursorial bipeds both 
for maneuverability on the ground and thrust when leaping. This condition 
served for the "basis" of the wing, as you put it."

Don-- I agree. I am not sure that this has been mentioned, so I add that any 
insulating/display/camoflage structures (feathers or proto-feathers) on the 
extremities of cursorials would, through selection against drag, tend to 
"migrate" to the trailing edge of the limb, creating a potent "selective 
synergy" toward a functional wing. In other words, the trailing edge is subject 
to display/camo/thrust selection pressures, that combine to enlarge the 
structures on the trailing edge versus the leading edge. It also seems 
intuitive that selection to reduce drag on leading body areas might increase 
the R factor...

Don

----- Original Message ----
From: Patrick Norton <ptnorton@suscom-maine.net>
To: dinosaur list <dinosaur@usc.edu>
Sent: Monday, February 20, 2006 8:13:57 AM
Subject: Re: tiny theropod on a tree trunk question

David Peters wrote:

>Once the carpals bend (rotate), then you have the basis for a wing, not
>before, hence the question

Exactly right, which is why I never said anything about a wing. I spoke only 
of selection for aerodynamic thrust, which, among dinosaurs, was very likely 
happening as soon as feathers began appearing on the distal parts of the 
arms. Elongation of the distal arm feathers and rotation of the hand would 
have been highly selected for among fast (flightless) cursorial bipeds both 
for maneuverability on the ground and thrust when leaping. This condition 
served for the "basis" of the wing, as you put it.

PTN

----- Original Message ----- 
From: "David Peters" <davidrpeters@earthlink.net>
To: "dinosaur list" <dinosaur@usc.edu>
Sent: Monday, February 20, 2006 7:07 AM
Subject: re: tiny theropod on a tree trunk question


>
>
>
>
> Jaime and Patrick have, unfortunately, put the cart before the horse.
> Step back a few million generations.
>
> Once the carpals bend (rotate), then you have the basis for a wing, not
> before, hence the question. Case in point: Colugo.
>
> David Peters
> St. Louis
>
>
> PS.
> Jaime Headden wrote:
>
> In regards to the squeeze he wrote about, the extant mammalian "sacrum"
> is
> not homologous to the ancestral amniote sacrum. As for frogs, they
> ancestrally
> posses a single sacral vertebra and the identity of this vertebra is
> apparent
> even in juveniles and fossils. The fused element of the urostyle is a
> case of
> fusion of proximal caudals, as is apparent when observing the ontogeny
> of
> Urodela, to the sacral to anchor the hip muscles, not the presence of a
> fused
> sacrum itself (hence the term urostyle, from _uro_ "caudal" + _style_
> "rod").>>>
>
>
>>>>
>
> Try [functional] analog, Jaime. Not homolog.
>
>
>
>
>