Re: feathered ornithopods?

["Tim Williams" <twilliams_alpha@hotmail.com>]

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.

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.

> > 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.


> 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.


> 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).

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


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



Tim

_________________________________________________________________
Send and receive Hotmail on your mobile device: http://mobile.msn.com