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Here are my own final comments on our
monthly installment of the "birds are NOT dinosaurs" debate...
I've made the point in the past that in
some situations, paraphyletic groups should be recognized for grades which
differ in a generally conistant way in morphology, lifestyle, or whatever, from
one or more descendant clades, simply because there is no way discuss such
evolutionarily, ecologically etc. interesting groups using strictly monophyletic
terms. However, being based on rather arbitrary criteria, its hard
to create tidy paraphyletic groups which can be broadly
agreed upon; for this reason, they should be appraoched with caution.
They certainly can't be defined as tightly as monophyletic taxa, and
definitions should remain flexible. It probably gets easier at lower
taxonomic levels because you are looking at smaller and therefore potentially
less diverse groups that may easier to outline; genera are probably the
most frequently encountered example of this, as any analysis which includes
polyspecific genera is likely to have one or more turn out to by
paraphyletic.
However, I do NOT extend my tolerance of
paraphyly to long accepted paraphyletic groups simply on the basis of
familiarity, and here is why: As more fossils are found,
paraphyletic groups which group generally morphologically similar taxa
that differ in an interesting way may potentially become more clear
and better understood (although the edges of the group are also probably going
to become more fuzzy).
The same doesn't apply to familiarity,
because it fades with time. After another 50 years of people
recognizing that birds are descended from dinosaurs, people won't give much of a
crap about CALLING them dinosaurs, just as not many people today seem
to give a crap about Apatosaurus supplanting Brontosaurus. Everyone knows
nowadays what Apatosaurus is, and the initial consternation stemming from
familiarity with Brontosaurus is long gone. By the
same token, birds are already generally accepted to be descended from
Dinosauria, don't really look very out of place among the broad but socially
acceptable diversity of Dinosauria, and there isn't much that all "non-avain
Dinosaurs" have in common with each other that excludes birds and justifies
eventually them getting thier own name (Dinosauria) exclusive of
birds. Public and what professional consternation remains will fade
as people become more familiar and comfortable with these facts. When
this happens, what do you suppose the next generation of vertebrate
paleontologists will think of the "public familiarity" of another generation
being used as a criterion for judging how organisms were
grouped?
LNJ
***************************************************************** Procrastination is the thief of time- Edward
Young
***************************************************************** Jeffrey W. Martz Graduate student, Department of Geosciences, Texas Tech University 3002 4th St., Apt. C26 Lubbock, TX 79415 http://illustrations.homestead.com/Illustration.html |