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There is a section of a basal sauropodomorph femur of material
referred to "Thecodontosaurus" figured in Benton et al. 2000 ("Anatomy
of Thecodontosaurus", in JVP) which seems to present very thin walls.

2010/2/14 Michael Mortimer <mickey_mortimer111@msn.com>:
> David Peters wrote-
>> Bennett (1996) did this. He noted that most of the synapomorphies between 
>> pterosaurs and Scleromochlus resided in the hind limbs, with little else to 
>> promote a relatioship. So he tested the removal of the hind limbs to see 
>> where pterosaurs might end up. I think it was a good test. It demonstrated 
>> that the position of pterosaurs within the Ornithodira was based on flimsy 
>> evidence. It's never a good fit when one is forced to say things like: 
>> "Pterosaurs appear suddenly in the fossil record." Adding fenestrasaurs to 
>> the Bennett (1996) taxon list showed that this previously untested clade had 
>> more pterosaur synapomorphies. That data has never been tested, only 
>> dismissed (by Hone and Benton 2008).
> While I agree the protorosaur hypothesis was not usefully tested by Benton 
> and Hone, saying that a relationship is based on flimsy evidence if it is no 
> longer recovered when hindlimb characters are excluded seems baseless.  Which 
> studies have been done eliminating hindlimb characters from other analyses 
> and comparing the results?  Most oviraptorosaurian characters are in the 
> skull, but does that mean they're a poorly supported clade?
>> Agreed. That's why you should look very carefully at the ornithodires and 
>> try to see if you can find an elongated fifth toe. If you can't find one 
>> among them, and you won't, it's time to look to other taxa. Also look for 
>> digit IV longer than III. That's the primitive condition in pterosaurs.
> You and your key characters.  By that reasoning, we'd exclude 
> therizinosaurids from Theropoda and sauropods from Dinosauromorpha.
>> Perhaps it does count for something. The skeleton of Sharovipteryx was 
>> hollow. That's a start. Be interesting to see how far back air sacs go in 
>> pterosaurs. Not sure that's been determined yet. Are they known in Triassic 
>> taxa?
> Hollow bones are often unrelated to pneumaticity, though the latter can cause 
> the former.  Basically every theropod has hollow limb bones, but almost no 
> Mesozoic theropod has pneumatized limb bones.  Bone wall thickness is 
> something that desperately needs examination in more taxa.  The old canard 
> about only theropods (and pterosaurs) having hollow bones is certainly false.
> Mickey Mortimer