Re: Sauropod ancestry?

["T. Mike Keesey" <tmk@dinosauricon.com>]

On Tue, 18 Jul 2000 HPB1956@aol.com wrote:

> 
> In a message dated 07/16/2000 DinoGeorge writes:
> 
> << Early sauropods retain all five functioning pedal digits, whereas in 
> prosauropods the fifth digit is reduced, vestigial, or lost (only a splint 
> metatarsal V remains). It is extremely unlikely that sauropods re-evolved a 
> complete fifth pedal digit from the prosauropod or herrerasaur condition. >>
> 
> Therizinosaurids seems to be generally accepted as theropods nowadays. If so, 
> doesn't this mean that the reexpression of the fith pedal digit in sauropods 
> isn't that unlikely?

Therizinosauroidea simply took an already-existing digit and put it
back in contact with the ground (so to speak). For Sauropoda to have
evolved from Prosauropoda, they would have had to redevelop a digit that
was lost.

A better analogy might be the "re-evolved" limbs of _Pachyrhachis_, if it
is a derived ophidian (which, AFAIAA, is still debatable).

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T. Michael Keesey <tmk@dinosauricon.com> | AIM <Ric Blayze> | ICQ <77314901>
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