I think that has a lot of variables. Crocodiles were on earth around 250 million years ago, the t rex around 68 million years ago. Crocodiles still breath our atmosphere.
That doesn’t mean other animals didn’t have different breathing parameters though.
Crocodiles may have also adapted over time to deal with the changes in our atmosphere, while the dino DNA would not have gone through those changes. They could handwave that problem by saying they combined it with some other DNA or modified it themselves (better hemoglobin?)
I think that has a lot of variables. Crocodiles were on earth around 250 million years ago, the t rex around 68 million years ago. Crocodiles still breath our atmosphere.
That doesn’t mean other animals didn’t have different breathing parameters though.
Crocodiles may have also adapted over time to deal with the changes in our atmosphere, while the dino DNA would not have gone through those changes. They could handwave that problem by saying they combined it with some other DNA or modified it themselves (better hemoglobin?)