stegosaur origins

[John Schneiderman <dino@revelation.unomaha.edu>]

Can anyone suggest a common ancestor for Stegosauria.  Scelidosaurus (the 
ornithischian parts of the type specimen) is currently considered an 
ornithopod.  So I'm looking for a more primitive form or something 
fabrosaur-like from the late Triassic or early Jurassic.
Also, is it possible that there existed a row of keeled plates much 
shorter than the massive spine/plates running down the back between the 
large plates.  I think that the large plates were firmly attached and did 
not have as much motion capabilities as Bakker suggests. Although the 
alternating plate arrangement is effective for thermo-regulation, I'm 
just not 100% convinced.

---John Schneiderman (dino@revelation.unomaha.edu)