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Re: Paradoxically temporal



At 08:46 AM 7/23/98 -0400, Thomas R. Holtz, Jr. wrote:
>>   Why does the fact that _Eoraptor_ appears later or contemporaneously
>>with _Plateosaurus_ in-and-of-itself disqualify it from being
>>_Plateosaurus_'s ancestor?
>
>At present, all known specimens of _Eoraptor lunensis_ occured too late in
>time to be **directly ancestral** to prosauropods.  In this particular sort
>of situation, Feduccia and Martin have made an excellent point: an ancestor
>MUST be older than its descendants.  (Of course, where they make their
>mistake is thinking that dromaeosaurids are advocated as bird ancestors,
>rather than bird sister taxa).  We have, at present, no fossils of
>_Eoraptor_ which are old enough to be _Plateosaurus_' ancestor.

   That doesn't answer my question, though.  *Why* do you say that the time
of appearance in the fossil record is a disqualifier given the vagaries of
fossilization and the fact that speciation can occur without obliterating
the ancestral stock.  Is it for the same reason put forth by Chris Brochu,
that you also use the phylogenetic species concept (which I presume, BTW,
is something from phylogenetic taxonomy?)?


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