re: E and P of pterosaurs - more comments

["Jaime A. Headden" <qilongia@yahoo.com>]

Dave Peters (davidrpeters@earthlink.net) wrote:

<DP: I mentioned a reconstruction, David. All you have to do is ask to see
it. It's unpublished, but that's okay. And it was based on a viewing of
the actual specimen in Italy.>

  Even so, a reconstruction is an interpretation. It would have to be
independantly viewed for proper and effective interpretation by anyone
else. It's not like some people agree on the same taxa or specimen viewing
it; skeletal reconstructions of the same taxa from multiple viewpoints
tend to vary in the small details, and if one were to use the skeletons to
code from, one would thus be getting different ideas of what is coded how.

<2. Let's code Campylognathus for "skull smaller than glenoid-acetebulum
distance." It appears in C. liasicus, but not in C. zitteli.>

  My comment on this would be that one form may be a younger animal than
the other, representing a larger head relative to trunk length than in the
other animal. This must also be taken into account. And if it's
ontogeny-based, the character can be relegated as (largely) taxonomically
uninformative, given the current samples of subadult and juvenile series
of all taxa of pterosaurs (virtually relegated positively only to some
species from the German Malm, and now to Argentina).
 
<3. Let's code Dorygnathus for "manual digit III longer than metacarpal
IV". It appears in SMNS 50164, but not in the Donau specimen.>

  Any positive evidence this isn't due to displacement? That the
metacarpal of one isn't pulled distal to the carpus, or in the other
proximal to it, where in crushing the metacarpal would not show any sign
of such displacement if viewed from a drawing or distant photograph?

<DP: I was disheartened because you didn't go deep enough, evidently.
Because when you start including phalangeal proportions and palate
morphology -- and alot more specimens --  your cladogram will start to
change.>

  I think if he did, every descision of coding would change. One takes
rather interesting steps when one looks at some pterosaur's skulls and
their palatal configuration, given that a very primitive,
non-archosauriform or an advanced, ornithodiran condition alters the
potential homologies of the identified elements. Possible fused bones or
split bones among taxa occur frequently in birds, at least, as among
multiple archosaurs, depending on function, and this needs to be examined
in more depth to regarding supposed identifications by any author. I think
first, before a coding analysis, an actually morphological study of the
palates of several pterosaurs should be undertaken, and at no other time.
This argument should be published prior to coding the palates.

=====
Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

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

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