re: David Marjanovic

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

I have a few last moment comments to make on the subject...

Dave Peters (davidrpeters@earthlink.net) wrote:

<Easy David. I was thinking a pre-publication photo had to be floating
around. And besides, you would be stunned what the pdf does reveal.>

  Unlike Marjanovic's observation, the papillae of the eggshell is
apparent at some degree in the close-up in the paper. As for the pdf, this
low-resolution jpg is low-quality, and at full-screen, the pixellation
(72dpi) is clear to the eye, so that the image can be copied line by line
with someone having a GOOD sense of color in some pixel-dependant image
program. However, the image reveals a mess of limb bones and a mass that
MAY be the vertebral column. I would be impressed at the ability of anyone
to determine through the published photo the segmentation of digits and
vertebrae, especially since this segmentation will occur at less than 2
pixels in length, and less so for any digits one might see. This makes it
difficult to interpret very much after the internet or the pdf images.

<This would imply post-independent or adult status. I know that in all
other verts embryos develop bone tissue and I was raised and educated on
the notion that the same would hold true to pterosaurs. This follows the
observation of 40 examples, so I can only follow and report the data.>

  Since the only data that would support that this specimen is more mature
than was originally implied would be Peters' own observations that
pterosaur babies with cartilaginous skeletons can cling to their mothers
or show any sense of adult morphology, it is highly doubtful this specimen
_can ever_ "test" the theory of finding babies littered around virtually
every Solnhofen and Liaoning specimen (as in, cartilage holds onto muscle
_very_ poorly, including the ungual phalanges, so that clinging would have
the adverse effect of tearing at and distorting the skeletal frame as well
as the unguals themselves). Despite all this preservation of impressions,
even when the adults show _clear_ impressions of bone, the "infant"
impressions are not at all clear to the naked eye, when they are
supposedly quite large. Testing the nature of these beyond the condition
of being pits or cracks or pedestalling on split slabs has YET to be
performed.

  This specimen offers a test that fits the observation seen from all
crown amniotes: embryos and neonates have ossified skeletons, otheriwse,
their bodies would not satisfactorily support their organs or even stand
up. Pliability of cartilage can be tested at home with any Thanksgiving
turkey or Christmas goose, or wrack of lamb, etc..

<This suggests we consider taxa that have, as adults, proportionately
large eyes.>

  ...

<Again, I was raised and educated to consider all the  tiny forms with a
short rostrum and big eyes as juveniles. I was surprised as anyone to
discover that pterosaurs were somewhat different.>

  This negative allometry of the eye and braincase occurs relative to the
snout in nearly all amniotes. It is unlikely that it would be otherwise.
In the chance that a growth series is observed to prove this erroneous for
a species where someone can actually _confirm_ the observations, this
would be nice. However, this condition has yet to occur. The second
statement should make it plain why the interpretation of soft-body
skeletons as inclusions and not artifacts of fracture or geology needs to
be more thouroughly tested before ascribing identities and ages to these
things.

  As for Wang and Zhou's track record: though Zhou Zhonghe more often than
not has made a few misidentifications regarding the birds he has helped
describe, more often than not, they were still birds, their bones were
apparent, and the artifactual nature of the bulk of the material he has
been involved with has been minimally almost NIL. Wang Xiaolin primarily
works with pterosaurs and non-avian dinosaurs, as he has been involved
with Xu Xing on a record of rather curiously _accurate_ material. Aside
from the fact that the record of the authors is unimportant to the actual
material at hand. The material shows an articulation of humerus, forearm,
and set of elongated "phalangeal" bones that defies interpretation other
than the wing finger of a pterosaur. This is done without the authors on
the paper being called into question as a possible excuse to dismiss the
interpretation.

  Cheers,

=====
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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