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Re: Dino Birds (was Re: Dinosaur = extinct animal)
In a message dated 7/12/99 10:50:51 AM EST, email@example.com writes:
<< Dinogeorge@aol.com wrote:
> In a message dated 7/12/99 9:00:56 AM EST, firstname.lastname@example.org writes:
> << The overall point is that paraphyletic assemblages, above the species
> level, are subjective, have no biological reality, and are not
> recognized in modern systematics. >>
> Paraphyletic taxa certainly have "biological reality," whatever that is. If
> monophyletic taxon A and included monophyletic taxon B are "biologically
> real," then so is the paraphyletic taxon A-B, the set of organisms that are
> in A but not in B.
No, it isn't, because we're subjectively deciding what to subtract from
Not to be misunderstood: If A is >any< monophyletic taxon and B is >any<
monophyletic taxon included in A, then the taxon A-B is as "real" as A or B.
Deciding which B to subtract from A has nothing to do with the "reality" of
A-B. It has only to do with the >utility< of formally declaring A-B a taxon.
You can form a perfectly real and well-defined taxon by removing, say, the
genus Tyrannosaurus from Theropoda (or at least as perfectly well-defined and
real as Tyrannosaurus and Theropoda are), but is it useful to do so? I'd say
that virtually nobody would think so, and so we don't have a taxon called
"Nontyrannosauria." But if A is the monophyletic Dinosauria and B is the
monophyletic Avialae, then there certainly is great utility in retaining a
taxon A-B for "nonavian dinosaurs." Taxonomies have other uses than merely
being phylogenetic mirrors.