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Comment by GalenErso | Hacker News Reader

Sea life may bounce back, but gigantic aquatic fauna seems to be on a permanent decline. Megalodon, mosasaurus, liopleurodon, and dunkleosteus are extinct and... nothing like them is evolving again? All the above animals evolved after the Tr-J mass extinction event. So why are we not seeing similarly large animals evolve today? Blue whales and Carcharodon Carcharias are cool, for sure, but they're just not the same.

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The blue whale is the largest known animal to have ever existed on this planet not just today. We had plenty of very large (larger than extant) land animals until the holocene extinctions began. The Paraceratherium (a extinct animal like a rhino) was head to toe 24feet! (7.4m). (perhaps higher oxygen levels as others might have pointed out played a role too in sheer size.)

https://en.wikipedia.org/wiki/Holocene_extinction https://en.wikipedia.org/wiki/Paraceratherium

I suspect it has to do with a decline in atmospheric pressure. The pressure is lower now, and it makes the physics of large living creatures more difficult.

I wonder if the fact that we have much lower oxygen content now than 100-50 millions years ago might be a factor here. Also, the fact that despite "climate change" we are living in one of the coolest periods in Earth's history: https://www.climate.gov/media/11332

this is "cold comfort" .. plenty of long geological eras were highly poisonous or unstable. It is annoying-or-worse to see a one-liner that implies that rapid increase in overall temperatures is OK or even "normal"

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