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RE: Gastroliths (Theropods) -Reply



On Tue, 20 Apr 1999, Augustus  Toby  White wrote:

> >>> "Thomas R. Holtz, Jr." <th81@umail.umd.edu> 04/20/99 07:27am >>>
> 
> Gastroliths are minimally a basal archosaur character (crocs got'em, birds
> got'em, so the simplest evolutionary answer is that the most recent common
> ancestor of cros & birds had'em).
> 
> Correct me if I'm wrong, but I think this kind of reasoning from parsimony 
> only works when you're dealing with homologous structures (physical or 
> molecular).  It loses a great deal of force when you apply it to
> behaviors, or to non-homologous structures since there is no necessary
> implication of a common genetic basis for the trait.  I study
> paleontology.  You study paleontology.  I can almost promise you that
> our LCA did not.

But I can pretty well guarantee that your and Tom's LCA did sneeze, and
yawn, and cry, and perform other instinctive behaviors, since these are
(at least partly) genetically determined, much as swallowing rocks
probably is for archosaurs in general.

-Nick P.