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Re: Wilkinson's new pterosaur paper, Cunningham, Habib



Dave Peters (davidrpeters@earthlink.net) wrote:

<My whole point is
  1. strict unbiased observation (precise tracing);>

  Tracing is biased, however, as it is based on perception of what blur means
what. Viewing a slab and sampling the material is the only way to KNOW what is
what on the slab. In the case of unpreserved membrane, in examples like
*Sordes*, you have heavy carbonaceous remains on the slab that in some places
are not fully preserved. But you do not have ONE slab, you have TWO, and
furthermore slabs are not all exposed or even buried in a single plane, as has
been explained before rather more than a few times. Missing material from just
behind the elbow can be solved by somewhat of a simple technique, if there are
aktinofibrils which disappear before they reach the elbow, but would seem to
extent to the elbow's "vanishing point". As these have been hypothesized to be
evolved muscle tissue, I doubt they are NOT attached to the limb itself in any
way, and perceiving an actual hole would tend to be viewed as a first
impression improbability that would require testing (and proof) to theorize
about function from.

  <2. reconstruction in all configurations (folded, open, partially open);>

  Moreover, reconstruction based on not artificially condensing the wing when
the finger is extended, or considering the ability to lengthen the chord when
the wing is in any shape, which the aktinofibrils suggest is possible. Simply
rotating the wing shape as preserved on the slab out and filling in the lines
based on a perceived narrowness proves very little.

  <3. interpretations must be supported by data (evidence).>

  I wholeheartedly agree. See above. Practical experimentation and first-person
examination a must in this field, however. A good deal of people from Jim to
Conway to Unwin and Kellner are working on physical models under all hypotheses
to test aerodynamic shape and controls of wing planform and function.

<Just come up with a single specimen that does not follow the rule and I will
grant you that variation in inboard wingshape can and does occur.>

  I would throw the old standby out as evidence, but it would be tossed away
due to the same tracing "evidence" that has been used before, but I'll do it
again: *Sordes pilosa* defies nearly all Peters' arguments about wing design
save one: It can, in fact, have a narrow-chord wing that extends to the ankle.

  Cheers,  

Jaime A. Headden
http://bitestuff.blogspot.com/

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


 
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