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Re: Archaeopteryx running



 

Williams, Tim wrote:

And still are important.
True.
 However, at the earliest stages certain abilities
of theropods conflicted with the demands of flight and perching.  These
include grasping prey with the hands, and running easily over the ground
with the aid of a long tail and cursorial pes (including a short &
"out-of-the-way" hallux).
I don't see either of those as much of a handicap to flight.  The feathered tail obviously could have supported most of the weight of the heavy hindlimbs when in flight (plus the weight of the tail itself), to keep the cg and center of lift located optimally.  The hands could on occasion act as vg's to accomplish much of the same effect as an alula.
 I think _Archaeopteryx_ endeavored to retain all these skeletal traits and, at the same time, dedicate its integument to
aerial flight.
Most likely.
 Modern birds took a different approach: they sacrificed their ancestral grasping and cursorial abilities to focus on aerodynamics.
Are ostriches and emus a functional example of this trend?  More seriously, once you develop an effective supracoracoideus, you no longer need the cursorial ability (this has to do with landing, not with trees down or ground up theories). And once you develop the alula, you no longer need the hand to assist with vortex control during flight.
However, the question......to what degree............. development of the wing...decoupling of the forelimb.....from
predation - (a) and (b) being closely associated.
I dunno.
If the earliest stages of aerial flight simply involved the predator leaping
into the air
Why would we make this assumption?  Why not make a number of other assumptions?  For example an effort to increase the available zenith angle during a turn.
.........or as the culmination of a short sprint),
Why make this assumption either?  There are also other effective ways to get into the air from the ground.
do we really need to be too concerned with aerodynamics?  I'm not
saying aerodynamics were not important - God forbid!  Quite the opposite.
Aerodynamics came up whenever the predator tried to make its leaps higher or
longer or more precise - such as for snatching prey.
Why do aerodynamic benefits have to be limited to higher, longer, more precise leaps?
 BUT - I think
_Archaeopteryx_'s "mosaic" anatomy (feathers vs skeleton) tells us that the
first birds were prepared to "hold back" on improved flight abilities in
order to retain the superb ground-running and prey-catching abilities given
to them by their maniraptoran ancestors.
What is there about Archaeopteryx anatomy that indicates that it was a particularly inefficient or ineffective flyer?  If it was so inefficient, why do kinematic calculations indicate that it was as effective a flyer and glider as some modern birds, even if not quite in the same league as Diomedes exulans?
As I said, later birds took a very different path - and the world is a much better place for it.
I'd be more prone to phrase it as ' - and the world is a much different place for it".  The same holds for the loss of my favorite beasties, the azhdarchidae.  I wish they were still around.

Jim