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uprightedness (was Re: SICB Report, part 1 (long)]



Birds fly with their body parallel to the ground.
As James will point out, it's a damned efficient shape for flight.
So the mechanics of flight do NOT call for uprightedness.
However most birds are upright.  
The ratites seem to be less upright than many of the other bird lines
(which is why they make such good models for theropods) but most ratites
don't fly and may not have in their lineage for a very very long time.

I suggest that uprightedness was a prequisite for losing the tail.
You can fly (abeit awkwardly) with a tail for drag but the length can
get in the way when you stand upright.

How upright was Archie?  Caudipteryx?  Seinoeropteryx?  Those danged
duckbird things of the Eocene?
How much tail did each one have?

-Betty

> Nicholas J Pharris wrote:
> 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.>