Re: really big question

[Tim Williams <twilliams_alpha@hotmail.com>]

Cliff Green wrote:

>      My point is that Pelicanimimis is, according to the information that 
> I
> have received, VERY well preserved, as in one of the most completely
> preserved of any dinosaur ever found. The authors claim that it is so well
> preserved, that what they first thought were feather impressions, turned 
> out
> to be muscle fibers.

Many well-preserved fossils (i.e., those that preserve some soft tissue) 
differ on exactly what kind of soft tissue is preserved: horn, nails, skin, 
feathers, hair, viscera, ova, eyes, stomach contents, etc.  Certain innards 
of _Scipionyx_ are well-preserved, but not the external anatomy.  For 
_Archaeopteryx_, we have well-preserved limb and tail feathers, but there is 
no trace of the rest of the "soft anatomy", either internal and external 
(with the exception of the claws' keratin sheath and body contour feathers 
in some specimens).  This also applies to many dinosaurs (avian and 
non-avian) from the Yixian and Messel strata.  For _Santanaraptor_, both the 
epidermis and muscle fibers are preserved in the fossil.  For 
_Pelecanimimus_ we have a gular pouch and muscle fibers, but AFAIK nothing 
else.

> The best preserved fossils at the site show feather and
> scale impressions. Pelicanimimis is on that best preserved list, and shows
> niether.Thus, according to the simplist answer, it didn't have any.

I don't mean to sound sarcastic (my apologies if it comes across that way), 
but _Pelecanimimus_ must have been covered in something.  At the moment we 
have no good evidence what that "something" looked like.  The suggestion 
that _Pelecanimimus_ did not have a fuzzy or downy body covering (even 
limited to certain parts of the body) is based on negative evidence.  It 
could have had this sort of integument, or it could have had 
_Santanaraptor_-like polygons set in its epidermis, or both.

Therefore, I'm not so sure that we can say that _Pelecanimimus_ can be put 
on the "best preserved list".  Perhaps something about the gular pouch made 
this part of the anatomy more resistant to decay and more amenable to 
preservation.  Or perhaps further study will reveal more of its integument.

I hope that made sense.

Cheers

Tim

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