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Re: preliminary ornithischian classification

In a message dated 6/9/01 5:16:46 PM EST, kinman@hotmail.com writes:

<< The only really "BIG" question in my mind now is whether or not 
 Ankylosauridae and Stegosauridae (both sensu lato here) are really sister 
 groups or not.   Apparently some workers think Stegosaurs are sister group 
 to cerapodans (in a clade excluding ankylosaurs).  I have no strong opinion 
 one way or the other at the present. >>

There's no real basis for grouping stegos and ankylos together except for 
their armor and a few minor anatomical features. Since I think dermal armor 
is plesiomorphic to ornithischians and sauropodomorphs and variably expressed 
in all of their subclades, it's not a useful character for uniting stegos and 
ankylos (might as well unite them with titanosaurians into the bargain, eh?). 
In terms of pelvic and limb structure, stegos seem closer to 
marginocephalians and are likely the closest known sister group to 
marginocephalians plus ornithopods. But their appendicular anatomy really is 
unique to them.