Re: Brrr, bone chilling paleopolar summers(Polar dinosaur growth and other new papers)

[Dann Pigdon <dannj@alphalink.com.au>]

On Sat, Aug 6th, 2011 at 11:07 PM, GSP1954@aol.com wrote:

> Conditions in Australia look even worse, with evidence for permafrost (at 
> least down south). There were polar sauropods that could not migrate north 
> because of the ocean down under. 

It should be noted however that sauropod remains have not been found as far 
south as Victoria. 
Tom Rich once made a prediction that they would never be found there, and so 
far he hasn't been 
proven wrong. 

The modern Antarctic circle (below which there is at least one day per year of 
24 hours of light or 
darkness) is at 66.5 degrees south latitude. According to palaegeographic 
reconstructions, the 
Victorian deposits in Australia would have been at around 75 degrees south 
latitude in the Early 
Cretaceous, which would have been well inside the modern Antarctic circle. 
Although I suppose 
the degree of tilting of the planet in the EK might have been different, thus 
putting the polar 
circles (as they are defined now) at different latitudes than the present.

It seems that Australian sauropods might be better described as 'sub-polar'. If 
the extensive 
sauropod tracks along the coast of Western Australia are anything to go by, 
then sauropods may 
well have been the only Australian dinosaurs that did migrate - although not in 
and out of 'true' 
polar conditions.

Given the basic body shape of sauropods (lending them high surface area to 
volume ratios for 
their mass), it's not surprising that they seem to have avoided extremely cold 
conditions. They 
may not have been able to eat enough food to offset the loss of body heat from 
their necks and 
tails. There is, after all, a limit to how much food you can cram through a 
comparitively small 
mouth in a set period of time, and low vegetation quality during a time of the 
year with constant 
darkness wouldn't have helped things. Juveniles would have suffered even more 
in such frigid 
conditions, as their surface area to volume ratios would have been even higher.

-- 
_____________________________________________________________

Dann Pigdon
Spatial Data Analyst               Australian Dinosaurs
Melbourne, Australia               http://home.alphalink.com.au/~dannj
_____________________________________________________________