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Re: SICB Report, part 1 (long)

On Thu, 14 Jan 1999, Betty Cunningham wrote:

> Birds don't stick out behind at all but MANY still stick out in
> front-including the early forms we DO know.
> What balances birds in this? the upright S-shaped posture of the neck
> over the shoulder and keel

> -Betty Cunningham

One thing I haven't seen mentioned in this thread yet is that modern
birds, unlike non-avian theropods, have (nearly) immobile femora that, as
far as I can tell, stick straight forward, effectively displacing the
"hip" joint (actually the knee) to a position under the wings.

My suspicion would be that at the same time as aerodynamic considerations
forced the shortening of the tail in the line leading to modern birds,
balance was maintained through the locking of the femora in a forward
position (effectively sacrificing a leg segment in return for an
aerodynamically suitable tail), along with  some reorganization of the
posture, as Betty suggested.
Nick Pharris
Pacific Lutheran University
Tacoma, WA 98447