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Re: interesting Triassic stains (A BIT LONG)



Dear Silvio and List members,

The nasty tricks that shadows and cracks play can usually be tested by

1. symmetry
2. placing the suspected part into a reconstruction
3. cladistic similarity to sister taxa
4. cross-checking with those who have the specimen at hand.

All of the characters I've seen in Eudimorphodon ranzii fit the first
three categories. The fourth I've asked Fabio to check on a day ago. No
reply as yet.

That a crack appears on the sternal complex coinciding with the
posterior wing line is not surprising considering that the complex is so
thin it has holes of decay randomly sprinkled on it, resembling moth
damage. Also the criss-crossed clavicles that make up the leading edges
are visible.

Suspecting that cracks, glue and taphonomic stains can turn into a pair
of symmetrical wings, a lyre-shaped pelvis, and two sclerotic rings
ideally sized to fit the orbit is a bit like suggesting that a monkey
can type Casey at the Bat, or even the first line, on the first try.

On the other hand, I have to confess, my methods do fail at times. It's
rare, but it happens. Recently it appeared that Istiodactylus had a pair
of vestigial medial teeth on its premaxilla, a pattern shared with other
ornithocheirids such as Coloborhynchus. So tests 1-3 were met. I sent
the results of a scan (taken from an inch-wide photocopy!) to one of our
list members closer to the specimen and discovered that what I thought
were teeth were scratch marks. The proof came in the form of a larger
picture that showed other possibilities however, in the form of possible
empty alveoli. The story ends here, unfortunately, and I will keep you
aprised of the situation as we examine the suspected alveoli.

Here possibilities are being explored using _all_ available methods --
kind of like a scientist.   :  )   Nothing is being published yet. This
is still a conversation. Thus, dismissal of methodology, in my opinion,
is premature.

After all, if I discover only one valid overlooked thing using my
method, then the method works to that extent. And every night I discover
something new and previously overlooked -- often previously overlooked
by me!

For instance, I think I just found a winged ant/wasp in the mouth cavity
of Sharovipteryx. I sent a jpeg to Sharov's son, also an entomologist,
to verify the find. I'll let you know what the results are.

A scientist, even an amateur one, like myself, should not be afraid to
try and fail. That's why I'm very open about my observations.

Pterosaurs have remained mysteries far too long.

Here are some new interesting little possibilities that have appeared in
the last few weeks.

The dimunition of the tiny lateral toe in Campylognathoides may not be
convergent with that of pterodactyloids, but homologous. The
re-elongation of the fifth toe in Rhamphorhynchus and Dorygnathus
appears to coincide with the elongation of their teeth forming another
branch. Still there's a lot of convergence in the series.

Dimorphodon weintraubi is different enough from D. macronyx to warrant
its own genus. It's well on the way toward evolving into a dang big
anurognathid.

Longisquama has long, very thin, plumes emanating from its crest, making
it look more even more like a Mardi Gras spectacle, than previously
suspected.

David Peters
St. Louis
















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Re: interesting Triassic stains (A BIT LONG)



       To: dinosaur@usc.edu
       Subject: Re: interesting Triassic stains (A BIT LONG)
       From: Silvio Renesto <renesto@mailserver.unimi.it>
       Date: Thu, 27 Feb 2003 10:00:02 +0100
       In-Reply-To: <3E5AFF28.3731AD1D@earthlink.net>
       Reply-To: renesto@mailserver.unimi.it
       Sender: owner-dinosaur@usc.edu



What follows has not to be considered as a dismiss of David Peters ideas
in
general,  but as aimed to point out some flaws in  his intepretations of

Eudimorphodon, possibly due, at least in my very humble opinion, to some

weaknesses of the method:

At 23.29 24/02/03 -0600,     Richard W Travsky <rtravsky@uwyo.edu>
wrote:

Concerning a message by David Peters on stains in Eudimorphodon:
Ok, you got my curiousity going. I'd like to see tho not necessarily
correspond on it. Is there somewhere you could post a picture? Web site
or something?

everyone can see a picture of the specimen at this URL:

http://users.unimi.it/vertpal/galleriafossili/best-rettili/EUDIMORPHODON.htm

It's a bit a low resolution one but it works.

Concerning David Peters statements on Eudimorphodon I have to cast my
doubts about some assumptions

>In the recent past, I've been chided and ridiculed for "seeing things"
>in the stains and impressions I find in scans of fossil pterosaur
>pictures. Well, it's time to put the ole sore neck on the chopping
block
>again.
>In the often-pictured holotype of Eudimorphodon ranzii there is a
>wonderfully preserved skeleton on a slab and surrounding it are a
number
>of stains.
Absolutely not my intention to chop off your head David, but I recommend

you to look carefully at the actual specimen. From its discovery onwards
it
has loaded with various kinds of glue (arabic, that old one to stick
stamps
on envelopes and figurines on albums), paraloid  (a resin), and the hell

knows what else. Thus it has stains but sincerely I am dubious about
their
nature. In addition the matrix itself has different proportions between
organic matter and marly limestone from one spot to another....
In further addition a rather old fashioned mechanical preparation  with
a
vidian nail (that one for old record players, when music scratched, he
he)
has possibly erased anything that was not bone....thus the specimen is
not
exactly untouched..

>4. a larnyx

>5. a propatagium

>6. two narrow-chord wings, both attached to the elbows. One clearly
>crosses the sternal complex. The trailing edge looks like a crack.

Indeed, it has been considered as a crack so far.


  I didn't see all the other stuff on the specimen; Fabio Dalla Vecchia
looked at it much carefully than  I did, but seemingly he also missed
it.
Fabio where are you? There is nothing in your in your PhD dissertation
about this stuff?

>8. what Wild (1978) described as the prepubis appears to be the broken
>open head of the femur, so now the femur is no longer the "too short"
>anomaly it was. The "head " of the femur has only a small articular
bump
>without a constricted neck.
>9. the base of the coracoid expands into a delta ventrally.
>10.a complete pelvis
>11. and the real prepubis.

I have no problems to admit that previous authors may well have
misintepreted something here and there, it happens frequently, but I
feel
strange that both Wild and Fabio (this latter guy  is particularly
nitpicking and nearly nothing escapes from his observations) and, on a
second issue (I did not work on it)  myself, didn't realize such obvious

errors in Wild paper.  Also Kevin Padian saw the specimens.

Some final word of wisdom, if I can dare:
I  tried to work/play with photos and various methods with PC, as you
also
suggested, partly for interest and partly for fun, but I soon realized
that
shadows cracks and matrix artifacts often play nasty tricks: One can
eventually do something with photos only if the real specimen is at hand

for continuos cross-check. Otherwise it is easy to see things that
aren't
there or are different. And if you have the specimen at hand working
with
photos may eventually lose some significance.
All the best,

                                         Silvio Renesto


_
         "When they hear of the Way,
         The highest minds hurry up to practice it;
         The average minds think about it
         They sometimes feel it real and sometimes not;
         The lowest minds laugh at it.
         If they did not laugh at it,
         It would not be the Way."

                                 (Lao Tzu)


Silvio Renesto

Facoltà di Scienze
Università degli Studi dell'Insubria
Via Dunant 3
Varese
Italy
temporarily:
phone +39-02-50315511
fax     +39-02-50315494
e-mail:  renesto@mailserver.unimi.it
         Silvio.Renesto@unimi.it
have a look at our Triassic  website at
http://users.unimi.it/vertpal/index.htm





       References:
              interesting Triassic stains
                    From: David Peters <davidrpeters@earthlink.net>



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