Basal Ornithischia and Stegosauria

[Jamie Stearns <stearns5@cox.net>]

Given that I've got a request for something on Ornithischia, I'm putting 
some of it up now.

`---Saurischia
..`--+---Pisanosaurus
....|...`---Lesothosaurus
....|.....`--Stormbergia
....|.......`--Agilisaurus
....|.........`---Ornithopoda
....|...........`---Abrictosaurus
....|.............`--+--Heterodontosaurus
....|...............|...`---Lycorhinus
....|...............`---Pachycephalosauria
....|.................`---Ceratopia
....`---Scutellosaurus
......`--+---Tatisaurus
........|...`---Emausaurus
........|.....`--+---Huayangosaurus
........|.........|...`---Regnosaurus
........|.........`---Dacentrurus
........|...........`---Chungkingosaurus
........|.............`---Chialingosaurus
........|...............`---Kentrosaurus
........|.................`---Lexovisaurus
........|...................`---Tuojiangosaurus
........|.....................`---Hesperosaurus
........|.......................`---Stegosaurus
........|.........................`---Wuerhosaurus
........`---Scelidosaurus
..........`---Ankylosauria

I've probably made my share of mistakes here, especially given the recent 
idea that Chialingosaurus may be invalid due the holotype material being 
missing or something. And I've recently heard that Stegosaurus was the only 
stegosaur to lack shoulder spines, not sure if this is true. If it is, it 
would be the most derived of them all. Do Wuerhosaurus or Hesperosaurus have 
shoulder spines?