The dinosaur was in the early versions of My Book of Bible Stories and was omitted in later editions.
Since the Watchtower Society believes that mankind has only been on the earth around 6,000 years or so, I'm surprised they didn't omit the Woolly Mammoths from the illustration as well because (except for a small group of them that lived in the arctic until 4,000 years ago) I think the rest died out somewhere between 10,000 and 11,000 years ago. Then again, they also believe the arctic didn't exist before the flood so why the need for the woolly coat.
As long as they continue to teach that the flood was a literal event, I'll know they aren't the true religion.