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



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

Dipartimento di Scienze della Terra
Università degli Studi di Milano
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        Silvio.Renesto@unimi.it
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