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Re: Hot-blooded dinos



> From: pwillis@ozemail.com.au (Paul Willis)
> > >-Pole-to-Pole: yes, the dinos lived in the polar zones, where at least the
>wint
> > >er had  freezing temperatures. This is one of the most solid arguments
>favourin
> > >g the hot-blooded theory
> >
> > Becareful about using this type of logic in defence of homeothermy. For
> > example, one of the "near Polar" dinosaur faunas from southern Victoria
> > includes a labyrinthodont. So unless you wans to claim labyrinthodont
> > endothermy, it is more likely that paleo-polar climates were substancially
> > different from modern polar climates and could probably support large
> > ectotherms.
>
>There is alao the possibility of hibernation.  This is particularly
>likely in labyrinthodonts, which were "compact" enough to burrow
>underground to hibernate.  I seriously doubt if a tyrannosaur could
>manage to find a safe place to hibernate, and tyrannosaur specimens
>*are* known from the North Slope of Alaska.
>

Crocs and turtles are also known from the Victorian sites. While both also
have known abilities for hybernation, or at least a torpid state, neither
use this as a stratergy to survive in arctic conditions. The croc and
turtle material I have seen is unlikely to belong to species that would
migrate very far. And the palaeolatitude estimates I have seen for the
sites is around 80 degrees south. While I agree that this would have been
pretty cold, it could not have been as severe as similar latitudes today
and, the non-dinosaurian component of the fauna suggest a climate similar
to the Carolinas. However, according to Rich and Vickers-Rich, the 18O/16O
ratios indicate mean a paleotemp of between +5 degrees C and -6 degrees C.
This would seem much too cold for crocs and turtles so there has to be
something wrong here (either it is the 18O/16O palaeotemp data or
Cretaceous crocs and turtles had a very different biology to their modern
counteparts). Although labyrinthodonts don't have a modern counterpart and
they may have hybernated, I can't envisage them surviving in environments
as cold as the palaeotemp data indicates.

All I am saying is that there is something lacking in our understanding of
palaeo climatic conditions, particularly at high latitudes. Because of
this, discussion of dinosaur biology based on "polar dinosaurs" is fraught
with danger.

Cheers, Paul

pwillis@ozemail.com.au

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