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RE: feathered ornithopods?




-----Original Message-----
From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
Williams, Tim
Sent: Friday, July 19, 2002 9:27 AM
To: 'dinosaur@usc.edu'
Subject: RE: feathered ornithopods?


Tracy Ford wrote:

> I don't buy this polar winters theory.

I think we can be pretty sure that both the Earth and the Sun were in the
same relative positions as they are today (give or take), and that the Earth
tilted on its axis as it orbited the sun.  Therefore, that part of the
planet near the poles would be exposed to prolonged darkness during the
winter season - including the southeastern portion of Australia (see below),
which was just a stone's throw from Antarctica.  Sure, the Mesozoic was
warmer than today - but does anyone doubt that areas within the Antarctic
(and Arctic) circles during the Mesozoic had winters that were not as long
and dark as modern Earth's polar winters.  That's got to have an effect on
temperature (i.e. downwards).<<

No doubt on the long dark winters, but that does not automatically equate to
freezing winters. Since the Earth was warmer and lacked polar caps, IMHO
would also mean a warmer dark winters.

> The paleo botanist shows a warm climate.

All year round?  The vegetation here in Iowa changes from lush to skeletal
in the space of 6-8 months.<<

But is it the same kind of vegetation as was during the Mesozoic? We don't
know how the plants acted seasinoally, may have been different than today.

>The thing is Australia was always in the lower southern hemisphere.
> Cambrian to now.

> Placoderms, eurypterids, ammonites, mosasaurs, plesiosaurs, sauropods,
> labyrinthodons, theropods, you name it, lived in Australia way down
> under.

Yep, but most of these critters lived in the sea. <<

Pardon, sauropods, labyrinthodons were sea animals?

>> Also, nobody has argued that prolonged cold temperatures is an obstacle
to the existence of life;
only that polar dinosaurs may have special adaptations for enduring the
winter cold - such as insulation, or migration.<<

Or it was just warm enough where they didn't have to have the insulation or
had to migrate.


> I don't get why the Early Cretaceous is specifically targeted for
> being 'cold' when all the time period it was down there.

>>I don't believe it is the case that Early Cretaceous Australia is being
specifically targeted as 'cold'. <<

Really, then why the couple of dozen papers by the Rich's etc, on JUST the
Early Cretaceous? Seems to me it's the big target.

 >>It's just that the Mesozoic terrestrial fossil record from Australia is
heavily biased in favor of this time
(Aptian-Albian) and place (SE Australia), so most discussions on this topic
are centered on the Eraly Cretaceous.  The Aussie hypsilophodontids and
Koonwarra feathers, for example, both share this provenance.<<

And Sauropods! Where they feathered or insulated also?

Tim



Tracy L. Ford
P. O. Box 1171
Poway Ca  92074