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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.  

Back to work.

Tim


------------------------------------------------------------ 

Timothy J. Williams 

USDA-ARS Researcher 
Agronomy Hall 
Iowa State University 
Ames IA 50014 

Phone: 515 294 9233 
Fax:   515 294 3163