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On Sat, 01 Mar 2003 17:52:56 -0800, Cliff Lundberg wrote:

[...]

>>SJ>A main reason is the typical Gondwanan distribution of the Ratites, e.g.
>>>emu, cassowary (Australia), ostrich (Africa)

I meant to include "Elephant Bird (Madagascar)", since, contrary to popular
opinion, Madagascar never was joined to Africa but is an independent fragment
of Gondwana.

>>SJ>and rhea (South America)
>>>which are flightless and primitive, yet true birds. The exclusively
>>>southern distribution of that other flightless bird, the penguin, supports
this.

CD>I wouldn't be so sure that Ratites are primitively flightless. Those wings
>look to me like vestiges of flight-capable wings. Why would such wings
>evolve at all in a primitively flightless bird?

[...]

I haven't the time to answer the rest of Cliff's post now, but by "flightless
and primitive" I did not mean they were *originally* flightless. I assume
that ratites are *secondarily* flightless.

But OTOH, there is evidence that ratites *were* originally flightless (see
tagline). I have no problem either way. But it would of course enhance
the Gondwanan origin of birds theory if the ratites were originally
flightless, since then it would be *most* unlikely that birds arose
flighless in Laurasia and then swam across the ocean to Gondwana! I
will look more into this.

However, the important thing about Stahl's quote is that anatomically,
especially in their palate, ratites are so distinct from all other birds that
T.H. Huxley (who in fact was the first to propose from their comparative
anatomy that birds arose from dinosaurs), placed ratites "in the superorder
Palaeognathae" and all other "birds ... he housed in the super order
Neognathae."

Steve


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"In supporting his hypothesis, Nopcsa called attention to the early
existence of birds called ratites, which are good runners but poor fliers.
Included in this category are the living ostriches, rheas, cassowaries, emus,
and kiwis and the extinct moas and elephant birds. Since remains of ratites
are known from the beginning of the Tertiary period, Nopcsa regarded
these terrestrial birds as primitive forms, closely related to the cursorial
avian stock in which he thought flight had first appeared. He was not alone
in judging the ratites to be archaic types. Huxley had upheld this idea in the
1860s, saying that the structure of the ratite palate was more primitive than
that of flying birds. In ratites, he pointed out, the pterygoid bones extend
straight forward to meet large vomers, whereas in other avians the
pterygoids articulate only with the palatine bones, the vomers having fused
completely and diminished in size. So convinced was Huxley of the
significance of the structure of the palate that he based his classification of
the birds upon it. The ratites he placed in the superorder Palaeognathae,
and the birds without the pterygoid-vomerine articulation he housed in the
super order Neognathae. The separation of the ratites from the supposedly
more advanced birds was broadly accepted. More than 60 years after
Huxley published his theory, P.R. Lowe reviewed and defended the thesis
that the flightless birds were relicts of avian populations whose members
had not yet evolved the ability to sustain themselves in the air. He argued
that in addition to having a primitive palate, ratites like the ostrich fail to
develop certain of the traits that characterize the advanced birds. They
produce only downy plumage, akin to that which in neognathous birds is
hidden by the contour feathers as the animals mature, and they continue to
show the sutures between the skull bones that vanish in neognathous forms
as growth is completed. Lowe believed that the absence of the clavicles in
the ostrich and the short coracoid elements in all the ratites proved their
direct relationship to the flightless, bipedal archosaurs." (Stahl B.J.,
"Vertebrate History: Problems in Evolution," [1974], Dover: New York
NY, Revised Edition, 1985, pp.370-371)
Stephen E. Jones sejones@... or senojes@...
Home: http://members.iinet.net.au/~sejones
Group: http://groups.yahoo.com/group/CreationEvolutionDesign
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