No iirc the air back then had way more oxygen and way more carbon dioxide which allowed for a warmer climate and the animals/plants to grow larger. Same with t

No iirc the air back then had way more oxygen and way more carbon dioxide which allowed for a warmer climate and the animals/plants to grow larger. Same with the ancient giant insects, their bodies would not allow them to survive today on such little oxygen which is why insects are all tiny today.