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----- Original Message -----
Sent: Sunday, February 11, 2001 3:59 AM

2: Cheeks were extensive throughout the Ornithischia and were possibly absent
in only the most basal forms such as Lesothosaurus and Pisanosaurus.
What about Stegosaurs?
In "Vertebrate Paleontology in Utah" there is an articles of  S.A. Czerkas in which the author stated that the more derived Stegosaurs (es. Kentrosaurus, Chungkingosaurus and Stegosaurus) possess a derived condition known as the "dorsal lamina", which is a thin plate of bone formed by the dorsal margin of the dentary, it lies lateral to the teeth row and obscured at least the posterior half of the teeth row in lateral view. Apparently this condition is much less developed in the most basal Stegosaurs such as Emausaurus, Regnosaurus and Huayangosaurus, and in the latter it's so small that most of the dentary teeth are visible in lateral view, except for portion of the last few. Czerkas stated that this "dorsal lamina" could imply that the more dervied Stegosaurs possess a extended beak along the dentary that excluded the possession of cheeks.
Marisa Alessandro
"Volounteer of Paleontological Museum of Monfalcone"
Via Achille Grandi nÂ18
Tel:039-0464-434658 Email amaris@tin.it