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AW: New MANIAC book is out!
> Looks fractally wrong to me. Cooling trend? The evidence
> for polar ice is from the Aptian and Albian, isn't it?
> There's none from the Campanian or Maastrichtian, AFAIK.
And even if - the Milankovic tilt/precession cycles didn't just stop under
"warm age" conditions. So one would naturally expect the glacial/interglacial
cycles to occur even in the Mesozoic. Of course, without significant glaciation
there cannot have been glacial advance, or any notable biogeographic effects
At present I wouldn't think that there is evidence of evolutionary significant
(as in "adapt or die out" or "enforcing speciation") glaciation in the Mesozoic
at all. A few glaciers in inner Antarctica are easily avoided by migration, and
with precipitation being as high globally as it must have been under such
conditions, there can't have been extensive desertification in the "glacial"
In an ice age (as the one we are in now), every glaciation is bound to have
significant effects. The distinctness of the fauna east and west of the
Cordillera (i.e. the entire range, not just the Andes) is an indication of what
The only conspicuous effect of glacial/interglacial cycles in "warm age"
conditions would be marine transgressions/recessions, the
introgressions/recessions of the Erromanga Sea may be such a case. But even
these would be less pronounced than what happened in the last 20 Ma, when
entire epicontinental oceans formed and disappeared. The Interior Seaway
certainly would have expanded and shrunk a bit every with a cycle of a few 10
Ka, but it does not seem to have disappeared altogether (or even for the
largest part) until close to the Cenozoic. And that was not because too much
water became tied up in glaciation/expanded as it warmed, but due to plate
tectonics (which ultimately seem to be the main "switch" for ice age vs warm
So yes, you presumably did have cooling/warming cycles that had some effect -
mainly in the form of land bridges appearing and disappearing. But a Late
Mesozoic cooling trend that was evolutionarily significant, especially to
*flying* theropods? Can't see robust evidence for this at present.
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