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Re: Arms into wings



--Original Message-- From: tsg94001@uconnvm.uconn.edu <To: Thomas R. Holtz,
Jr. : Wednesday, March 03, 1999 09:13 PM



>[Tom said:]
>>
>>However, you are suggesting that the pattern is: grasping ->
??unknown?? ->
>>flying.  In fact, what the morphological studies of _Archaeopteryx_ and
>>_Confuciusornis_ hands suggest instead is: grasping -> grasping +
flying ->
>>flying only (with the "handy birds" Archie & _Confuciusornis_ representing
>>the middle stage).

What they suggest to me are:
  climbing + predation  ->
  climbing + predation + gliding ->
  climbing + predation + aerofoil gliding + thrust-flapping ->
...and from then on, gradual loss of climbing + predation.

>
>Oh no - I understand that the earliest birds (like Archie &
>_Confuciusornis_) used their wings for BOTH grasping and flying.
>Later/other avian lineages dispensed with the grasping bit.  However, in
>some pre-_Archaeopteryx_ stage the forelimb must have gone through a
>grasping + ??unknown?? stage, and this ??unknown?? was the seed that gave
>rise to flying.

Gliding.


[snip]
>
>On the face of it (and pushing cladistic analyses aside),

[surely some mistake here!]

> the scenario is
>rather attractive.  For example, the feathers of _Caudipteryx_ and
>_Protarchaeopteryx_ have symmetrical vanes.  Based upon the phylogenetic
>position of these critters (particularly _Caudi_ as a possible
>oviraptorosaur), the symmetrical feathers came first and gave rise to the
>asymmetrical feathers used by _Archaeopteryx_ and other birds to fly.  But
>what's the use of symmetrical feathers?  It could be that _Protarchae_ and
>_Caudi_ are secondarily flightless, and that the symmetrical feathers
>evolved from asymmetrical, flight-giving feathers.  The asymmetrical
>feathers necessary for flight evolved via another route.

Right on.

>
>Or - the symmetrically-vaned feathers were useful for short, fluttering
>"hops" off the ground.  In which case the symmetrical feathers came first.
>I'm not very knowledgeable on the functional morphology of feathers so I
>won't push this one too far.

Now the fly-swat theory has been shown to have been "never-existent", there
is no justification for the "circuit and bumps" scenario.  Short hops into
the air do not escape a predator - they'll probably be waiting for you when
you come back down!


>
>I wonder what would happen if all flight-related skeletal characters were
>coded as one in cladistic analyses.  When birds lose their ability to fly,
>more than one character may revert to the "primitive" condition (shorter
>arms, longer legs, reduction of sternum, loss of keel).  If certain
>flightless theropods are descendents of primitive flying birds, then
>distinguishing genuinely primitive states from secondary loss of
>flight-associated characters could be tricky.  I don't envy you
>number-crunching cladistic analysts!  ;-)

That makes enormous sense since if the component features are not
independent (as one of the alternative hypotheses would claim), separating
them invalidates the statistical methodology - and as Kevin Padian reminds
us, we wouldn't want to be anything but methodologically rigorous, would we?


--Original Message--From: Pharris Nicholas J <pharrinj@plu.edu>To:
TomHopp@aol.com : Thursday, March 04, 1999 02:26 AM


>On Wed, 3 Mar 1999 TomHopp@aol.com wrote:
>
>> In a message dated 3/3/99 5:18:39 AM, Tom Holtz th81@umail.umd.edu
writes:
>>
>> << as Padian & Gauthier showed back in 1985, the predatory
>> strike of a eumaniraptoran forelimb uses the same basic movements in the
>> same sequence as the flight stroke: it would be a synchronized movement.
>>
>>
>> So they're to blame for "predatory strike," which may well be a figment
of
>> their imaginations that has been propagated into near-gospel on this
list? Oh
>> . . . .
>>
>> Maybe I'm a gadfly, but who the heck has ever seen a "predatory
strike?">>
>
>Anyone who's ever observed a praying mantis, for one!
>
>I imagine the strike of non-avian maniraptoran theropods as being similar
>to this, the arms folded against the body, bird-style, until the moment of
>the strike, which, as Dr. Tom noted, was accomplished in one swift,
>coordinated move.



I wrote on the 8th Feb last year:

~The prey of animals which flick something out, is always taken by surprise
~while within range of the extension: insects caught by chameleons, frogs
~and mantids, and fish caught by squids' telescopic arms are seldom fleeing
~at full speed.  Dromeosaurs could not hunt by creeping up to within range
~of such a flick; for one thing it would bump its nose against the prey
~first.

I still don't see this as a particularly useful adaptation for catching
Tenontosauri.  Mantids actually press the prey between what would be the
hand and the forearm of Deinonychus (or whatever the supposed creature is).
The special wing folding mechanism doesn't bring the claws to face the
forearm, but into more of an oblique sideways orientation.  The muscles for
doing this - the ones in the forarm - would... well the Tenontosaurus might
die laughing I suppose!