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----- Original Message -----
Sent: Wednesday, June 18, 2003 5:12 AM
> For example, one class
> (Reptilia) can give rise to another (Aves); why not? Descent doesn't mean
> >must< include the descendant group within the ancestral group.
When we have only holophyletic taxa, our decisions are only singly
arbitrary: we have to decide where to let Aves begin. When we allow
paraphyletic taxa, our decisions become doubly arbitrary: we have to decide
where to let Reptilia end _and_ Aves begin. Therefore I prefer the former.