How about some actual science

[SomeJackleg]

Indeed. During the Carboniferous that I mentioned in my post, O2 levels were at 35% or so of the atmosphere, as opposed to the current 21% - almost 175% of current oxygen levels.

O2 levels were also higher during the Triassic when the first dinosaurs appeared O2 was at about 12 to 15%, middle of the Jurassic is when the big ass plant eaters showed up and O2 was at about 26-28% the giant plant eaters  short fat ones  and long neck ones, near the end of the Cretaceous the bad ass meat eaters showed both the big ass ones and the little ones.

they say that the the loss of O2 levels was part of the reason lager dinosaurs died out it was harder for the to breath. and the little ones turned into birds.