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Brrr, bone chilling paleopolar summers(Polar dinosaur growth and other new papers)
I was completing my energetics chapter for the complete dinosaur recently
and realized that the climatic data in last year's Spicer and Herman paper in
triple Paleo is really cool (pun intended) because it does a real number on
what little is left of the idea that dinosaurs had some form of reptilian
bradyenergetic ectothermy. It also does in the notion that high latitude
dinosaurs migrated towards the poles in order to enjoy the beneficent summers.
The presumption has been that although the polar winters were nasty the
summers basked under the warming rays of the midnight sun and balmy
temperatures that even reptiles could operate within. The theory was that it
been worthwhile for gigantothermic dinosaurs to come up from winter
habitats to the south to enjoy this reptilian dinosaurian nirvana.
Problem with the giganothemic scenario is that on the Alaskan north slope
inhabited by pachyrhinosaurs, edmontosaurs, tyrannosaurs, ankylosaurs, small
ornithopods, troodonts etc July average temperatures were in the 50s F, and
rarely got into the 70s while occasionally dropping into the 40s and 30s. To
that add that it was cloudy all time most days. Blame it all on that
Pacific Cold Gyre that blocked warmer air from the south and generated
clouds. This entirely precludes the reptilian heating by air temperature and
basking system no matter how large or small the herp is. Which is why there
has never been found a single bradyenergetic croc or lizard tooth or turtle
shell piece along with the tachyenergetic dinosaurs, birds and mammals. The
winters were brutal, with no sun for three months and average January temps
below freezing, allowing repeat blizzards and the water to ice over (as I
showed in an illustration in PDW).
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.
So dinosaurs great and small similar to those living in warm latitudes were
living in habitats so harsh that even the summers were chilly and cloudy.
Yet their bone histology shows that Aussie and Alaskan dinosaurs were growing
about as fast as those in warmer climes, proof of high energy levels able
to cope with chronic cold even apparently without surface insulation in
There is no way that dinosaurs further south than the North Slope would
expend all the energy needed to migrate north in the spring-summer when by
staying put they would enjoy more warmth, more sun, and more food. It would
been maladaptive. The only dinosaurs that put up with the crappy polar
summers were the ones already stuck there year round the poor dears. Give them
This means that any "documentary" that shows dinosaur "families" making
epic journeys from lower latitudes to cavort and gambol in a polar summer
paradise are as bogus as a bad Car Talk diagnosis. There is no evidence that
polar dinosaurs migrated long distances, they stuck it out in the winter and
then ate as much as possible in the warmer months to heat up their bodies and
try to make it through yet another year.
And the hypothesis of low metabolic rate dinosaurs is dead, dead, dead.
Bakker was right.