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Bird origins



George Olshevsky writes:

>In a message dated 95-11-22 14:04:42 EST, jdharris@lust.isem.smu.edu (Jerry
>D. Harris) writes:
>
>>        Well, all is not lost...there's still the undescribed Korean
>>"archaeopterygid," also purportedly Late Jurassic!  ;-)
>
>We'll just see about that.

May I just risk the wrath of the Gods with the following comment:

It seems to me that the question of the origin of birds is becoming (or
continues to be) a sort of ideological tug-of-war, just  at a time when the
first really important clues to that origin to be found this century are
emerging from Spain, China and other places.

What it looks like from this remove is that instead of the fossils being
carefully examined with an open mind by all interested parties, they are
being tossed about like basketballs.   For example - the question of what
Protavis is seems to be determined not by what the remains actually show but
what the proponents want to believe about them.  If you are a Martin
follower or accept GO's views that birds evolved in the Triassic, then you
are likely to "see" birdlike characters in Protoavis; if you are not of this
view you see other things.

When this gets to the stage of making value judgments about fossils before
the data is even presented, I think it is time to sit back and breathe
deeply a few times.

>From the point of view of this non-palaeontologist all I can see is the
following:

1.  There are some Triassic fossils that show arguably birdlike features
(though some of these, like Longisquama, are too highly derived to have been
bird ancestors);

2.  There are no clearly accepted bird fossils predating Archaeopteryx;

3.  There now appears to have been a major radiation of birds in the late
Jurassic, but what this says about when (or from what form) this radiation
started is unclear;

4.  I have yet to hear that any of these fossils more closely resembles one
of the putative Triassic "protobirds" than it does Archaeopteryx (but such a
resemblance would certainly be very interesting if it were to, in fact, be true)

5. There are extremely strong similarities between Archaeopteryx and various
maniraptorian dinosaurs, though most of these postdate Archaeopteryx by a
considerable period.

I admit my tendency is to fall into the birds-are-dinos camp, but what I
conclude from the above (if it is correctly presented) is that we just don't
have enough information yet (particularly about Triassic forms) to determine
for certain just how birds first developed, but that (given all the new
discoveries) we may not have long to wait.  Perhaps waiting, without judging
or looking too anxiously for support for our pet theories, may be the best
strategy for uncovering the facts.
--
Ronald I. Orenstein                           Phone: (905) 820-7886 (home)
International Wildlife Coalition              Fax/Modem: (905) 569-0116 (home)
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