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Re: Feduccia ORIGIN



From: Gothgrrl@aol.com

 > He isn't saying that an "already-flying" animal is required for the
 > development of feathers, but that feathers evolved not from a
 > short-forelimbed, cusorial predator (such as an early dinosaur), but
 > from an arboreal, long-forelimbed diapsid.

He seems to be ignoring the possibility of a long-forelimbed, arboreal
*dinosaur*.

Long-forelimbed we have, and in forms apparently close to the ancestry
of birds.  We call them deinonychids.  Other, slightly more distant,
examples include troodontids and ornithomimids.  What is the relative
arm size in dryptosaurids???

To me a small arboreal troodontid or deinonychosaur seems quite
possible. (In fact I am not sure I can confidently say _Troodon_
itself is NOT arboreal).

 > He's saying that it's difficult (and perhaps impossible) to
 > construct a sound model whereby feathers evolved in a ground-up
 > scenario.

This assumes that feathers evolved originally for aerodynamic purposes

If feathers originated to provide insulation, than arboreality is
irrelevent.

Now, I *do* agree that evolution of flight from a non-arboreal ancestor
is unlikely, if it is evemn possible.  But I do not see how this rules
out dinosaurs.

In short Feduccia is erroneously combining the ground-up theory of the
origin of flight with the dinosaur theory of the origin of birds. The
two are not necessarily attached.

swf@elsegundoca.ncr.com         sarima@ix.netcom.com

The peace of God be with you.