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More on formal paraphyletic groups (Was: Greg Paul's new (or newly named) iguanodonts)
Tim Williams writes:
> BTW, I have no conscientious or ideological objections to naming
> paraphyletic taxa, in principle. But I suspect that in practice
> these paraphyletic groups could become more trouble than what
> they're worth. By definition, paraphyletic groups could only be
> 'diagnosed' by characters they *don't* have, rather than characters
> they do have.
Ah, come on, who diagnoses any more?
(Just joking -- mostly.)
Yes, for sure: the diagnosis for a paraphyletic group would precisely
"is diagnosed by the diagnosis of the larger clade but not by that of
the smaller clade".
> We could see a paper containing sentences like "Birds (Aves)
> probably evolved from Thecodontia, given that primitive birds share
> the following characters with thecodonts..."
Well, so? Such confusion is just as possible now: "Birds (Aves)
probably evolved from thecodonts, given that primitive birds share the
following characters with thecodonts..." The cure is clear thinking.
Yes, our choice of nomenclature can help, a little with that; but it
can't solve the problem. (Not that I don't like the idea of a system
of nomenclature in which is impossible to make incorrect statements
/o ) \/ Mike Taylor <firstname.lastname@example.org> http://www.miketaylor.org.uk
)_v__/\ "I have challenged the entire quality assurance team to a
Bat-Leth contest. They will not concern us again." -- Klingon