Re: What is biomechanics? (or, The Truth About Flying Snakes - Was: Re: science and philosophy)

[Silvio Renesto <renesto@mailserver.unimi.it>]

At 18.19 23/09/02 -0700, you wrote:

Not strictly related to origin of birds but morphology related as well.

>   Nope ... quite the contrary ... that data I have contradicts it. I
> myself never supported it. As I do not support *Longisquama* flying by any
> present data. Or even gliding. So far, no study shows what appear to be
> radiating slats could even produce a sustained drag or possess a paraxial
> resistance to torque that would in anyway resist gravity.
I agree that Longisquama was not a glider (contra Haubold and Buffetaut , 
1987), but it may have been a parachuter as an aside effect. I try to 
explain better:  those  elongate appendages  perhaps were mainly  for 
display. However, some drag could have been induced to slow down speed 
during  falling (a bit more if really they were paired and could have been 
spread a little) like the fluffy tail of non-gliding squirrels, it is not a 
gliding-parachuting adaptation per se, but works on occasion. Being the 
appendages on its back, close to the center of the body, this becomes more 
feasible if Longisquama had some device to avoid rotating on its own center 
of gravity like maple fruits , . Perhaps  an elongate or deep tail might 
have helped avoiding this.
If  this was only an aside effect like a safety device for incidental falls 
or  L.  jumped down from tree branches at will I don't know but I would 
vote for the first hypothesis.

>   I know of some references that have drawn differences in animals that
> glad versus parachute, and the snake and frog are both considered
> parachuters, but presently lack them myself -- I will try to look these
> up. The distinction has been to support with anatomy a direction-based
> definition, above or below 45 degrees.

one reference about this is
Milton Hildebrand,  1988  Analysis of Vertebrate Structure Third Edition, 
Wiley & Sons: at p. 571 he distingushes gliders from parachuters in this way.

All the best

                                        Silvio


The voice from the lake then asked
        "which is the strangest thing of all?"
Judisthira replied
"Every day men see other men die,  they see the chariots with the corpses 
and the fires, yet they keep  living as they were immortals, this is the 
strangest thing of all"

                                                        (from  Mahabharatha)

Silvio Renesto

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