Some kind of Parrot-Lizard

Based upon SMF R 4970; skull restored from P. mongoliensis

Psittacosaurus sp.

    The specimen SMF R 4970, ascribed to genus Psittacosaurus, but yet to be assigned to any species, is most notable for its facinating skin.  This Psittacosaurus is covered with a fine mosaic or tiny scales, or scutes, with the shoulders, back, and neck spotted with larger structures for ornamentation.  Strangest of all, the tail of this Psittacosaurus sports a number of long, thin spines or quills, which grow in a single row from the bace of the tail almost ot the tip.  These spines are too flexible to inflict much damage on predators, but they are usefull as a display structure.  A Psittacosaurus bristling with such quills looks far larger and more menacing than one without, and the sound made by swishing this spiny brush back is distinctive.

Thanks to Luc J. "Aspidel" Bailly for emailling me a copy of the Naturwissenschaften article.
Other sites containing pertinent information:

• Marco Auditore's Psittacosaurus
• Luis Rey's New Chinese Revolution II
• Øyvind M. Padron's Psittacosaurus  
• "Bristle-like integumentary structures at the tail of the horned dinosaur Psittacosaurus" by Gerald Mayr, D. Stephan Peters, and Olaf Vogel.  Published in Spring, 2002, by Naturwissenschaften.