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Re: Re: Sterna, Whales, and Evolution



>Which is exactly why trying to break the monophyletic Dinosauria up into a
>paraphyletic Dinosauria and a monophyletic Aves is such a unuseful idea!
>(Which was how the discussion began).

This is certainly true if you are trying to say something about phylogeny.
However, as I noted earlier, it is certainly "unuseful" to reduce all bird
families to tribal level to make them consistent with a dinosaurian taxonomy
if you happen to be an ornithologist -0 just as I assume it would be
"unuseful" for you to treat dinosaurs as a subgroup of Crossopterygian
fishes (where the exact sane problem arises - breaking a presumably
monophyletic Sarcopterygii up into a monophyletic Tetrapoda and a
paraphyletic group including lungfishes, coelacanths and "typical" crossops.
I am still puzzled as to how to construct a taxonomy that is
phylogenetically accurate and practical for use.

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.

Which presents me with a problem I have never quite understood.  Let us say
that you have, say, a genus of ten closely-related and very similar species.
One of those species - and only one - becomes the ancestor of a new and
highly-differentiated radiation.  The other ten go extinct.

Now - is the base species of the new radiation excluded from the genus with
the other ten species?  Must the whole of the new radiation, no matter how
differentiated and diverse it becomes, be included in the stem genus of
which it forms a nested subset?  If not, why not?
--
Ronald I. Orenstein                           Phone: (905) 820-7886 (home)
International Wildlife Coalition              Fax/Modem: (905) 569-0116 (home)
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