Jurassic period had FOUR TIMES the atmospheric density !
One of the four parameters for flight is "lift" a function of wingspan and wing area. Pterodactyal flying reptiles had 11 meter wingspan and todays Peruvian Condor has a 5 meter wingspan. Doubling the wingspan would double the area, and only be possible by having four times the air density. This far denser air mass would also reduce the lung to body mass ratio and reduce overnight heat loss by the planet, and by the larger massed dinosaurs.
Extrapolating past life proxy data has no way of accounting for massive variations like this. We know that our atmosphere is constantly stripped by solar wind and eroded by radiation decay, like N14 to C14. If there was four times the atmospheric 65 million years ago, then previous eons would logically have had multiples of this value. There are very few constants in the Universe, and no point of perfect reference. We live in a false paradigm reality bounded by faux science, fake history, filtered news and financed by a fiat currency. Prepare yourself for a vastly different, expanded conscious reality that is dawning.