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RE: feathered ornithopods?




-----Original Message-----
From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of Tim
Williams
Sent: Saturday, July 20, 2002 11:08 AM
To: dinosaur@usc.edu
Cc: twilliams_alpha@hotmail.com
Subject: Re: feathered ornithopods?


Tracy Ford wrote:

>No doubt on the long dark winters, but that does not automatically equate
>to freezing winters.

Even within the Antarctic Circle?  100-150 million years ago, southeastern
Australia was not just on the fringes of the Antarctic Circle, it was
slap-bang inside of it.  Sure, the Mesozoic Earth was warmer than today -
but at 80 degrees lat. S, things must have gotten pretty frosty during the
dead of winter.  At the very least.<<

We do not know this for sure. This is an assumation due to modern times and
we can in no way know whether or not it actually did get frosty. We happen
to be at different ends of this.

>>The presence of labyrinthodonts in EK SE Australia doesn't argue against
freezing or subfreezing temps at this time and place.  Frogs (e.g. _Rana
sylvatica_) can survive the Wisconsin winter.<<

So can crocodilians (in Florida and Lousiania). But labyrinthodons had
scales (which may or may not work for or against a cold climate) not like
modern amphibians.

> > Yep, but most of these critters lived in the sea. <<
>
>Pardon, sauropods, labyrinthodons were sea animals?

*sigh*  I said "most" not "all".  Placoderms, eurypterids, ammonites,
mosasaurs, plesiosaurs all lived in the sea.  Sauropods and labyrinthodonts
did not.<<

Right and I just wanted to qulify my point. There are animals that weren't
marine and that is the point I'm tyring to make.


>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.

>>Tom and Pat Rich's area of expertise is the fossils of the Strzelecki and
Otway horizons of Victoria (in southeastern Australia).  Both horizons are
Early Cretaceous age, and (so far) the most dinosaur-rich sites in
Australia.  I think we can forgive the Riches for publishing extensively on
these sites.  I find the Riches' work fascinating.<<

So do I.


>And Sauropods! Where they feathered or insulated also?

First show me a sauropod that lived within the Antarctic circle.  AFAIK, all
the Aussie Cretaceous sauropod material comes from further north than the
Victorian sites - Hughenden, Winton and Maxwelton, all in Queensland.  Even
mid-Jurassic _Rhoetosaurus_ comes from Queensland (near Roma).<<

Hows about Lightning Ridge?

Sauropod indet

SMITH, 1999

Number: Not given.

Locality: Sheepyard, about 80 km west of Lightning Ridge, New South Wales
State, Australia.

Horizon:

Biostratigraphy:

Age: Albian Stage, Middle Gallic Subepoch, Upper Early Cretaceous Epoch,
Early Cretaceous.

Material: Caudal centra.
Note: Opalized.



Brachiosaurid teeth

SMITH, 1999

Number: Not given.

Locality: Lightning Ridge, New South Wales State, Australia.

Horizon:

Biostratigraphy:

Age: Albian Stage, Middle Gallic Subepoch, Upper Early Cretaceous Epoch,
Early Cretaceous.

Material: 2 teeth.
Note: Opalized.


Does New Zealand count?

MOLNAR & WIFFEN, 1994

CD 542

Locality: Exposed at Mangahouanga Stream, North Island, New Zealand.

Horizon: Maungataniwha Member, Tahora Formation.

Biostratigraphy:

Age: Campanian Stage, Senonian Subepoch, Gulf Epoch, Late Cretaceous.

Material: Fragment of a rib.

>>Prosauropod material is known from Antarctica (Early Jurassic age, I
think)
- maybe these had some sort of insulatory body covering.<<

Personally, I don't think it's a prosauropod, but part of Crylophosaurus.
The hand reminds me of Xuanhosaurus, but I haven't seen all the material.

  Why not?  The
feathers of birds and advanced maniraptorans, the dino-fuzz of basal
coelurosaurs, and the porcupine-spikes of _Psittacosaurus_ may all derive
from an integument that was primitive for the Dinosauria (and even deeper in
diapsid phylogeny).  "Nakedness" might be a derived condition, as exhibited
by large-sized dinosaurs: carnotaurs, tyrannosaurs, sauropods, hadrosaurs -
which are demonstrably not feathered or fuzzy or spiny*, based on skin
imprints.  This is the case for modern near-hairless mammals (elephants,
rhinos, hippos, whales etc), all of which evolved from more hairy
ancestors.<<

Sorry, I just won't jump on to that band wagon, yet. But you never
know...someday I may...


* Though diplodocids may have had dorsal spines - not sure of the status of
these structures.<<

Other than them being there, I can't say much on it either.




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