Bird evolution

[skeptix@cyberwarped.com (Leon Retief)]

The February 1998 edition of "Scientific American" carried a good,
very
readable article by Kevin Padian and Luis M. Chiappe, entitled "The
Origin
of Birds and their Flight."
It states : "Anatomical and aerodynamic analyses of fossils and living
birds
show that birds evolved from small, predatory dinosaurs that lived on
the
ground"
Clear illustrations show how birds evolved from Theropoda,
throughTetanuriae
and Maniraptora. Attention is paid to the development of 3 functional
toes,
the development of a 3-fingered hand, a halfmoonshaped wrist bone and
a claw
on the foot curving towards others, all characteristics found in
modern
birds.
The contribution of John Ostrom towards the acceptance of the idea
that
birds have theropod dinosaurs as ancestors is mentioned.
Padian and Chiappe state : "The cladogram shows that birds are not
only
descended from dinsaurs, they _are_ dinosaurs (and reptiles) just as
humans
are mammals, even though people are as different from other mammals as
birds
are from other reptiles."
Attention is paid to the development of avian flight and how it
probably
evolved from dinosaurian anatomy. Objections to the dinosaurian
ancestry are
noted only to be shot down by seemingly convincing arguments.
I enjoyed this article and thought that the whole matter seems to be
more or
less cut and dried, or as much as something like this can ever be.
However, I then came across a book review in the March/April issue of
"The
Sciences", in which Larry Martin reviews three books, by Alan
Feduccia,
Sankar Chatterjee and Pat Shipman.
Martin states : "In the great debate over bird origins, the dinosaur
connection is set to take a dive."
Martin also discusses the role of Ostrom in convincing paleontologists
that
birds descended from dinosaurs, but states that the pendulum has begun
to
swing back again, saying that new evidence contradicting this view is
beginning to emerge, quoting two recent articles in Science which show
that
dinosaurs are clearly distinct from birds. The three books under
review
discuss the situation, and Martin, with evidence which seem to me, as
a
non-paleontologist, to be equally convincing as that of Padian and
Chatterjee, refutes the viewpoint that birds descended from dinosaurs.
Martin feels that instead of being descendants of dinosaurs, birds
should
rather be regarded as cousins, descending directly from dinosaur
ancestors
called thecodonts.
In fact, Martin convincingly points out a number of apparent fallacies
in
the arguments advanced by the proponents of the dinosaur-bird
connection,
such as a seeming misunderstanding of some anatomical aspects given
much
weight by Padian and Chiappe.
Then (sigh) just as I thought my confusion was complete, I came across
the
following article in South Africa's Weekly Mail and Guardian for March
27 to
April 2. Entitled "Proof that birds grew from dinosaurs" it reads in
part :
"It was about the size of a turkey. It walked on two legs. It had a
long
tail and long neck and stubby forearms that ended in a single claw. It
certainly could not fly. Yet Suvuuia deserti could send feathers
flying all
the same.
According to the science journal Nature it roamed the Gobi desret 70
million
years ago and the animal - completely new to science - looks for all
the
world like a transition between a dinosaur and a bird.
(the fossil seems to be the first one found with a  skull - LR)
Their skulls show something found only in birds, called prokinesis :
the
snout moved up and down independently of the rest of the skull....It
is the
one thing that makes a bird a bird....It was one more bit of proof
that
today's birds are indeed the inheritors of the dinosaurs."

So then. What is one to make of all this?

Regards

Leon Retief
Bellville
South Africa