this post was submitted on 17 Sep 2023
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The atmosphere was different then.
That enabled animals to grow as large as they did, and it enabled massive pterosaurs like Quetzalcoatlus to exist. And even Quetzalcoatlus, which is much lighter and had much larger wings than T. rex, has been the subject of debate as to whether and to what extent it could fly. Both existed in the late Cretaceous period.
the atmosphere 66 million years ago wasn't that different to the atmosphere today, the reason why pterosaurs like quetzalcoatlus was able to grow to such massive sizes was because they had extremely light skeletons. higher oxygen levels did allow arthropods to grow to giant sizes during the carboniferous, but it would have little effect on how large vertebrates could grow.
Dinosaur lungs are much more efficient than mammal lungs. Their bones are lighter, too.
It's also why birds can fly so much higher and be so much larger than bats.
I'm not comparing dinosaurs to mammals though. I'm comparing them to pterosaurs. Or more specifically, I'm comparing the specific dinosaur in question (T. rex) to the largest and most likely to struggle with flying of the pterosaurs, (Q. northropi).
T. rex was, according to my quick search, at least 5000 kg. Q. northropi was just 250 kg at the higher end of estimates. The dinosaur had an armspan less than a metre, while the pterosaur's was in excess of 10 times that.
I wasn't responding to comparing dinosaurs to pterosaurs. I was responding to the part about them being big because of the atmosphere.
There's a number of reasons we don't have brontosaur-sized elephants. The differences in the atmosphere explains far less than hyper-efficient lungs and light bones.
Oh I see. Good to know!
It wasn't different enough that those chicken wings would let a 15,000 lb critter fly. It had more oxygen, which was helpful for letting critters get big (esp insects), but it wasnt physically thick.
That's the joke