In the Time of the Dinosaurs, 1963.
By William Wise.
Run-of-the-mill kid's book you might have borrowed from your
elementary school library. So-so illustrations.

Does this Struthiomimus on the left look familiar? At first I
thought that the book's artist, Lewis
Zacks, swiped it from a
George Solonevich illustration (on the right) contained in Craig's Dinosaurs
and More Dinosaurs. I guess it was the other way around,
however, as Dinosaurs and
More
Dinosaurs was
published in1965, whereas In
the Time of the Dinosaurs was published in 1963.
Index