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Early Jurassic ?Feathers

Tim Williams wrote:

> David Marjanovic wrote:
> >"..The trace of the Early Jurassic squatting theropod from Massachusetts
> >contains the pubic-abdominal imprint with the hair- or feather-like
> >impressions. ..."
> Ah, but as we all know, these are really just "macerated collagen fibers"
> aren't they.
> ;-)
> "Applying the Liliensternus and Dilophosaurus proportions of whole body
> length to foot length, to AC 1/7 footprint size, the trackmaker's length can
> be estimated as approximately 5 m."
> I wonder if this down-like body covering may have been seasonal.  Maybe
> theropods (especially, but not exclusively, the big ones) shed their "fuzz"
> in the spring and sprouted it again as winter approaches.  This might
> explain its apparent absence in the Bavarian _Compsognathus_ and its
> presence in _Sinosauropteryx_ of Liaoning.
> By the way, thanks for the reference David.
> Tim

Having spent a good amount of time with my face pressed close to ACM 1/7, I
must echo Paul Olsen's opinion that the structures in question are almost
certainly sedimentological and not biological.  I mentioned this to Gerhard at
one point--he was less than thrilled with that interpretation as you might
expect, but then he hasn't spent all that much time with the specimen.
Literature-based paleontology kicks us in the ass again...

Josh Smith
Department of Earth and Environmental Science
University of Pennsylvania
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