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Re: Re: Sterna, Whales, and Evolution



>> Anyway, isn't calling Dinosauria "paraphyletic" dependent on where you start
>> looking?  I assume that all animals normally called dinosaurs, no matter how
>> many lineages they produced, form a monophyletic group within Archosauria at
>> some level.
>
>I'm not positive, but you may be confusing "paraphyletic" with 
>"polyphyletic" here.  "Paraphyletic" means that a group contains animals 
>which are all descended from a common ancestor--but that not all the 
>animals descended from that common ancestor are included in the group.
>
>Does this help?

You are correct - I was confusing the two terms.  Sorry.

However - my problem still remains that the stem taxon of any node must be
either be paraphyletic by definition if it involves even two species, one of
which gives rise to a new heirarchy and one of which does not, or be split
into two based not on the phylogeny or characteristics of the species but on
the fact that one of them happened to have differeentiated descendants.
--
Ronald I. Orenstein                           Phone: (905) 820-7886 (home)
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