They say there must have been a higher concentration of Oxygen in the air to support the bigger bodies -- especially large insects because they don't breath. Maybe they're wrong though. This old dragonfly must have had a wingspan of 1.5 meters or more, so perhaps it could have absorbed extra oxygen through the extra surface area of its wings. I don't know about the turtle. Perhaps it just moved very slowly so as not to faint. Perhaps the dino's had some super gas & temperature exchange abilities, or maybe an oil-cooled dino heavy towing package. Another possibility is that they cut down on their need for oxygen by holding their breath and simultaneously cooling themselves with the gas expansion of continuous methane backfirings.