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Re: [Re: Theory on ornithoptering and could Archie do it ?]



> Archosaur J wrote:
> 
> >I'll make this short and sweet. Since Archeopteryx and origins of flight
> >aren't >exactly my best studied subjects, I apologize in advance for any
> >errors that I >might make.
> >
> >Okay so one of the big questions circulating through paleontology today
> >is: How >powered flight evolved.
>
Chris: 
> One needs to differentiate between flight and *powered* flight, they are
> two separate things.  Flight can be seen as simply keeping yourself
> airborn, and is surprisingly easy (given the correct power/weight ratio).
> Once a certain aerial speed is achieved (approx. 9 m/s) then simple
> flapping in enough to maintain flight.
> Power flight is an entirely different animal.  Power flight is the ability
> to take off from a standing start, to fly at very low speeds and to do
> aerial acrobatics.  Power flight is to flight what the 4 minute mile is to
> running. Just because you cannot run the mile in 4 minutes does not mean
> that you cannot run.  Similarly, just because a bird cannot power fly does
> not mean that it cannot fly.
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Ah I follow. I guess I should have stuck with ornithoptering.
======================================================================

Chris: 

The lack of a sternum in Archae is a bit of a red herring.  It is probable
> that the sternum was not ossified, but still allowed muscle attachment.
> Also, the new form has a small sternum.
> 
> Also it is unlikely that Archae was on the direct line to power flight,
> since it lacks a number of critical features such as ligament placement.
> 
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Still, didn't Archaeopteryx show signs of strong muscle attachments furcula 
wise. Sorta showing where large wing muscles started at before working their 
way down. 

Maybe I'm just getting this from an old source
======================================================================

Chris:

> >Now as for how powered flight in insects evolved. That's anyone's guess.
> 
> Ah this is quite interesting.  For instance did you know that the HOX genes
> for wing development are actually expressed in all segments, but is turned
> OFF in all but the segment(s) carrying wings?  This suggests that the
> ancestral insect actually carried the stuctures which were modified into
> wings on all segments. Specimens of fossil insects tend to support this.
============================================================================================================================================

I take it that you (like myself) are one of those people who can easily get 
caught up in subjects that they didn't intend to.

That bit on insect wing segments is intrigueing. Makes paleo-insects sound like 
Hallucinogenia. That invert has to be the weirdest of the weird. 

Aren't the wings of flying insects (extant forms at least) connected on the 
thorax only ?
======================================================================

Chris:

> It has been suggested that the original structures had another function,
> probably temperature control and experiments suggest that the size at which
> they become inefficient as temperature controllers (too big) is the size
> that makes a difference to falling insects.  Fossil insects show a series
> of these stucutures running along the back, but tapering so that the first
> is the biggest and the last the smallest.  Switching off the smaller ones
> would leave just the larger ones at the front of the body.  Also  . . .er,
> but I digress . . .
> 
> Chris
============================================================================================================================================

Which means that flies went one step further and turned off the second pair, 
leaving only stubs behind. Very interesting. And, unfortunately, very off 
subject. Perhaps this might do better off list.
Still very interesting discussion though.

Archosaur J


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