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RE: Granicones




-----Original Message-----
From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
Williams, Tim
Sent: Wednesday, February 20, 2002 2:18 PM
To: 'dinosaur@usc.edu'
Subject: Granicones


Returning to Purbeck granicones, and whether they belong to helodermatid
lizards or to ornithischian dinosaurs...

Says Barrett and Clarke (2000) of the Purbeck material:

"Although superficially similar to ankylosaur osteoderms in overall
morphology, no ankylosaur osteoderm possesses the TUBERCULAR SCULPTURE
present on the granicones. Moreover, ankylosaur osteoderms are considerably
thicker dorsoventrally than are the granicones. The sculpturing of the
granicones most closely resembles that present on the cephalic osteoderms of
helodermatid lizards, such as HELODERMA; the gross morphology of many
granicones is also consistent with this interpretation."

(The emphasis is mine.)

Then I remembered this, from a JVP paper by Anderson et al. (1998).  It
refers to the skin impressions from the tail region of a hadrosaur from New
Mexico:

"In general, the complexity of the radial sculpturing, specifically the
number of ridges and rugosity, increases with increasing tubercular size.
This specific type of ornamentation is not known from modern reptiles or
birds; however the TUBERCULAR MORPHOLOGY is similar to that of the lizard
HELODERMA."

Maybe the tuberculate morphology is typical of ornithischian skin, and the
"granicones" belong to _Echinodon_ after all. <<

Well, I just looked at figures of the Granicones in Don Gluts Dinosaur
Encyclopedia supplment no 2 (page 321 for those who have it) and they DO NOT
look like the skin of the hadrosaur.

Anderson, B. G., Barrick R. E., Droser M. L., and Stadtman K. L., 1999,
Hadrosaur skin impressions form the Upper Cretaceous Neslen formation, Book
Cliffs, Utah: morphology and paleoenvironmental context: In: Vertebrate
Paleontology in Utah, edited by Gillette D. D., Miscellaneous Publication
99-1, Utah Geological Survey,  p. 294-301.

Those large scutes have large 'serrated' edges, while the granicones have a
more oval base and are pointed. It just may be the authors who, actually
have seen the granicones and compared them to heloderma (strange concept
just looking at specimens for some) are right on this one.

Back to work.

Same here.

Tim


Tracy L. Ford
P. O. Box 1171
Poway Ca  92074