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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 
thereof. 

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" 
episodes either.

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 
you'll get.

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 
age conditions).

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.


Regards,

Eike

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