Earlier quoted context omitted.
>Why does “as if the waters had but newly retired” mean there’s a lot of water (and thus mud)? “As much mud as” clued me in, but I don’t get this part. "Imagine everything here was flooded and then the water leaves. The land would be left super muddy right? That's how much mud there is now". I'm surprised it's a difficult phrase, I'm not even a native speaker. The part with the stegosaurus is harder in that it relies…
I guess I could see that, but if all the water left, it could be dry like a desert too.. (although even though that was my initial interpretation, I did understand that's not what he meant) And yes even without the reference it's not that there's a literal animal there.
This is just a contextual interpretation thing. It's clear that's not what he means because he says it's muddy, so it must be the other thing. Also, it becoming a desert is more extreme, so in that case the writer would probably offer up a more detailed explanation.