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Re: scaly? skin



> From: Pat Grant (Library: Serials Catalog <PATG@vax2.concordia.ca>

> So, finally to the obvious question:  how certain are we that the
> blobby surface of ornithischian skin impressions represents scales,
> rather than glandular skin?  The ornithischian bits I've seen (mostly
> in tiny pictures) looked quite different, but the frog leather is
> still the closest I've seen yet.  And it's possible that there might
> have been more resemblance if the skin hadn't been stretched for
> tanning.  (However, I don't think I'll try suggesting that
> Protoceratops et al had to keep their skins damp...) 

How certain are we that ornithischian skin impressions represent scales? 
I'm no spokesperson for anybody but me, but I'd say we're about as sure
about this as we are about anything in dinosaur paleontology.  Perhaps you
are referring to photographs of the _Edmontosaurus_ mummy skin, which (in a
not very crisp photo) could be described as superficially similar to the
frog skin you describe, but if you could view the original fossil, you
might have a different opinion.

The tubercle patterns evident on the dinosaur skin impressions found thus
far suggest a mosaic of small, roughly hexagonal polygons (rather than
blobs) surrounding occasional larger, sometimes subconical tubercles.  Of
course, some dinosaurs had osteoderms as well, and for the vast majority of
dinosaurs, no skin impressions have yet been found.  But for most major
groups (aside from stegosaurs), we have at least one scrap of skin we can
study.

Notably absent from the record are tubercle impressions from small
dinosaurs, but the three _Sinosauropteryx_ specimens from China show clear
evidence of a covering of fibers (vaguely fur-like in appearance),
suggesting (as Gregory S. Paul has said all along), that small theropods
probably sported feathers (or protofeathers).

Considering that the tubercle-and-osteoderm-laden crocodilians are related
to basal dinosaurs, and the feathered birds are descended from theropod
dinosaurs, this makes sense.

Currie and Padian's _The Encyclopedia of Dinosaurs_ features an article on
_Skin_ by Stephen Czerkas, who knows this subject well.  If you can't
afford this book (who needs food?), perhaps your library has a copy of
_Discover_ magazine, March 1989, with the article, _Skinning the Dinosaur_,
by Don Lessem, which profiles Czerkas and shows a nice photo of ceratopsian
skin (_Centrosaurus_, I believe).

For on-line descriptions of a recently discovered fossil impression of New 
Mexico hadrosaur skin (remarkably well-preserved), I direct you to the
following articles:

_Skin Prints Impress Dino Experts_ at
www.sltrib.com/97/jul/071997/nation_w/27540.htm

_Fossil Allows Scientists to Feeel Dinosaur Skin_ at
www.uiowa.edu/~dlyiowan/issue/v127/i168/stories/A0201N.html

On the other hand, a dinocephalian, _Estemmenosuchus_ (not a dinosaur) was
discovered with a fossilized non-scaly epidermis which revealed details of
its complex interior structure, including the presence of glands similar in
appearance to sweat or scent glands.  Czerkas mentions this in his book
(coauthored with Sylvia Czerkas), _Dinosaurs: A Global View_.  In fact, the
Lessem article describes Stephen Czerkas slicing _Carnotaurus_ skin fossils
in the hopes of finding glandular structures!  Talk about searching for the
Holy Grail!  But he must not have found anything, or he surely would have
reported the news in his _Skin_ article.

Ralph Miller III <gbabcock@best.com>
"Not only were those things stupid, mean and ugly, but they were nakked as
jay birds!"