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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.