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Re: The Permian-Triassic Extinction

The dinosaurs did not even appear until the late Triassic. There were
no dinosaurs in the Permian

Yes -- I think the idea is that oxygen levels stayed low through at least the earlier parts of the Triassic, encouraging the evolution of the bird-style lung.

Are such lungs really worse at "processing fumes" than mammalian ones? I'd think the opposite -- there's no dead air in a bird-type lung, so everything that doesn't immediately glue itself to the tissue is swept out immediately, no? The canary in the mine dies first simply because it's so small (and has much higher metabolism than a lizard of the same size), I'd say -- note that gases rather than aerosols are involved here.

The extinction scenario... I think it's supposed to work like this: First the planet warms for unmentioned reasons. Then this stops the global ocean circulation. This means that no more oxygen reaches the deep sea, so anaerobic organisms prosper down there. Some of them make H2S, and this bubbles out and kills everything.

Global temperatures and ocean circulation seem to have something to do with each other -- witness the Oceanic Anoxic Events of the Mesozoic, especially the ludicrously hot Cenomanian-Turonian boundary --, but I don't quite know what that could be if there aren't any ice sheets available.