Re: BANDS > PADS vs. PALS

[Tim Williams <tijawi@yahoo.com>]

David Peters <davidpeters@att.net> 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. 


Yes, I know he did this.  But the point I made still stands: If most of the 
characters uniting pterosaurs with ornithodirans reside in the hindlimb, it 
might simply reflect the conservative morphology of the hindlimb.  In contrast, 
the pterosaur pectoral girdle, forelimb, and skull are highly derived.


> 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. 


The evidence is not "flimsy".  The hindlimbs of pterosaurs and dinosauromorphs 
show some striking similarities.  Hindlimb (especially ankle) morphology is 
critically important to archosaur phylogeny, so excluding hindlimb characters 
could be seen as a very bad idea.


> It's never a
> good fit when one is forced to say things like: "Pterosaurs
> appear suddenly in the fossil record." 


But they do.  So do bats.  Both groups (Pterosauria and Chiroptera) first 
appear in the fossil record as derived flying animals with the postcranium 
already comprehensively adapted to flight.  


> Agreed. That's why you should look very carefully at the
> ornithodires and try to see if you can find an elongated
> fifth toe. 


I can only re-iterate Mickey's comments regarding the fallacy of "key 
characters".




Cheers

Tim