[Swordmaker]

Re: more oxygen

There are some data to indicate that there might have been a higher O2 component in the atmosphere than in modern times. This might explain the ability of the megafauna to breathe through long passages from nostril to lungs (40ft!) but hyperbariatric oxygen studies don’t seem to show any benefit for strength enhancement but do show greater stamina of the muscles for extended exertion.

[aruanan]

This might explain the ability of the megafauna to breathe through long passages from nostril to lungs (40ft!) but hyperbariatric oxygen studies don’t seem to show any benefit for strength enhancement but do show greater stamina of the muscles for extended exertion.

Yes, but these studies are done on animals that are already adapted to a low O2 environment. What if the number of mitochondria were proportional to the O2 content? This would provide for much more ATP production per unit of tissue mass. Of course, their food intake had to be huge.