Sinosauropteryx ischium

["Ken Kinman" <kinman@hotmail.com>]

     Thanks to all who responded to the coelurosaur ischium question.  I 
was especially surprised to learn Sinosauropteryx has such a primitive 
ischium.  Maybe Nick Longrich is right that this genus might not even be a 
coelurosaur.  I haven't seen the just published Currie and Chen paper, but 
wonder if it might not at least support a more basal position for 
Sinosauropteryx (more basal than Ornitholestes, for instance).  And will it 
remain in Family Compsognathidae?
     Anyway, looks like the ischial characters only occur in subclades of 
Coelurosauria, but not in the whole clade.  And the "amphicoelous cervical 
vertebrae" character occurs in the non-coelurosaur Elaphrosaurus, so that is 
not so good either (and thus not a good reason to keep Sinosauropteryx in 
Coelurosauria).
     Would a better synapomorphy for Coelurosauria be the "Ascending 
process of astragulus more than 25% tibial length, and loss of transverse 
grooves across condyles"?   Or does that character too possess the 
nebulousness of the ischial characters.
              ----- Ken



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