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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.


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

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