Comment by aimor

When I was a kid I loved "Dinosaur Time" by Peggy Parish (and illustrated by Arnold Lobel). Originally published in 1974 it ends, "Dinosaurs lived everywhere for a long time. Then they died. Nobody knows why. But once it was their world. It was Dinosaur Time."

There was a revision to the book (not sure the date) with changes to the text and an expanded author's note at the end that talks about the new things we understand about dinosaurs including how Brachiosaurus are no longer believed to have spent their time in water to support their weight and how it's now believed an asteroid killed off the dinosaurs.

Original: https://archive.org/details/dinosaurtime00pari