I read somewhere that the oxygen concentration was much higher back then to a point where dinosaurs would not be viable in today’s atmosphere. They would have to stay in air tight enclosures. In a way that makes me feel safer about bringing them back. OH NO THE RAPTORS ESCAPED…. aaaand they suffocated. They’re dead now.
Dinosaurs should still be fine. The oxygen concentration really applied to animals with passive breathing systems like insects. Insects don’t actually breathe, they sort of just let the air directly oxygenate their blood. They can’t regulate breathing faster when they need more oxygen.
Dinosaurs have forced breathing through lungs. The blue whale is the largest animal to have ever lived including even the most massive dinosaurs, and blue whales still breathe air.
There’s not much difference between a velociraptor and a modern bird of prey either, other than the teeth.
That’s very likely true for insects and other creatures that don’t actually have lungs, and dubiously true for things with lungs. It certainly may have influenced their size to some extent but scientists far smarter than me have no reason to suspect they wouldn’t be able to breathe today.
I'd love to, but the half-life of environmental DNA is too short to fully reconstruct their genomes with our current technology. The most promising route would probably be to tinker with the genomes of extant crocodiles and birds to come up with a "close guess" of what dinosaur genomes may have looked like.
Actually, I just realized that it's drawn in a style that reminds me of Scott Johnson's (of Frogpants Studio and all his podcasts) art work. You might like some of his stuff.