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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