Re: The Permian-Triassic Extinction

[Tim Williams <twilliams_alpha@hotmail.com>]

Dora Smith wrote:

>  I understood that the shutting down of the ocean currents only became 
> possible as the planets assumed their current positions, around the end of 
> the Cretaceous era, or later.

I was a little confused, and I thought there was some astrological allusions 
here.  But I guess you meant "continents" rather than "planets".  :-)

> The shutting down of ocean circulation causes an ice age, not global 
> warming.

I'm not sure if I'm responding with another non sequitur, but with the 
continents jammed together to form one giant landmass (Pangaea), the 
terrestrial biotas were exposed to harsher, drier environments that resulted 
from a drastic decrease in the ratio of coastline to the vast interior.

A sudden drop in global temperature followed by global warming is usually 
attributed to the Siberian Traps.  The bolide hypothesis does not have much 
support when it comes to the Permian/Triassic extinction.

> The notion that that in turn causes ocean organisms to make hydrogen 
> sulfide is the original non sequitor.    What kind of common organisms even 
> make that amount of hydrogen sulfide,

Lots and lots of microbes do this.  I've worked with a few.  Stinky.

>  Is there any evidence that all dinosaurs from the end of the Permian time 
> had modern birdlike lungs?

No Permian dinosaurs (as others have pointed out, with admirable restraint). 
 There were dinosaurian ancestors back then, in the form of basal 
archosauromorphs (and maybe archosauriforms).

> If something wiped out most life on earth tomorrow, it might be hard for 
> creatures 125 million years from now to believe how highly evolved life was 
> when that happened.   There might be no primates around to tell the tale. 
> Just talking birds.

These talking birds might even take little mammals in cages down into their 
mines.

Cheers

Tim

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