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Re: New tyrannosaurus skeletal drawing



    Y'know, I always felt like I had a pretty good feel for working out
distortion, but I can't describe how it works. There's a lot of running your
hands along the grain of the bone and otherwise getting too personal with
the material. Even then, I still have to work from photographs to make sure
all the pieces go in all the right places. I've been pretty pleased with
comparisons made with subsequent finds, with one or two very embarrassing
exceptions. It is much easier with cataclastic deformation... plastic
deformation is the enemy.

    Distortion in skeletons, especially fossils, is pretty common, a point
not always appreciated. Recent skeletons often undergo significant
deformation during drying... Most of the specimens of Crocodylus I've seen
show significant separation along the interpremaxillary sutures from drying.
Once of the characters MSY Lee used in his work on the origin of snakes
turned out to be a bit of a problem: Olivier Rieppel pointed out
subsequently that the shape of the parasphenoid rostrum noted by Lee is due
to desiccation. Indeed, if you check out the Varanus on digimorph.org (which
was scanned whole), you'll see that the parasphenoid looks mighty different
in situ.

    Always with the interesting (and often overlooked) points you are, OH
Dan!

    Wagner


Jonathan R. Wagner
2625-B Alcott Lane
Austin, TX 78748

----- Original Message -----
From: <Danvarner@aol.com>
To: <dinosaur@usc.edu>
Sent: Tuesday, November 04, 2003 10:19 AM
Subject: Re: New tyrannosaurus skeletal drawing


> jonathan.r.wagner@mail.utexas.edu (Jonathan R. Wagner) asks:
>
> << Some reason I'm being put to the question, O Humble Dan? >>
>
>       No, just an interested but gentle jerk of the old chain, my dear
JRW.
> No agendas. Having worked for a number of years with specimens from the
Sharon
> Springs Member of the Pierre Shale, I find deformed fossils fascinating.
I'm
> always interested in how they look "corrected" and how those decisions are
> arrived at.
>        As an aside, I was surprised at how rapidly these effects can
occur. I
> once helped disinter a bison that had been buried at Wind Cave Nat'l Park
for
> ten years (the grad students took off when we got to the bright green
parts).
> The skull was already showing shear ALA the AMNH Tyrannosaurus skull. OHD
>