“Sorry, but if you even DOUBLED the air density...”
Notice I said much higher? Even doubling the pressure is not enough to allow the size of terrestrial animals (and extremely large fliers) we see in the fossil record, so it must have been much higher than even that. I’d guess we are talking on the order of several hundred atmospheres, at least.
Try mixing high pressure oxygenated atmosphere with combustibles!
I am ignorant.
Is there a method of determining ancient atmospheric pressure from the fossil record?