Would it have made sense in the 80s to believe there were dinosaurs 40 million years ago ?

I know we now know they went extinct 66 million years ago, and 64 millions is another date I’ve seen around, but how long how we known it was definitely way more than 40 millions ? I’m asking because it’s the date given in the the song “walk the dinosaurs” by Was (Not Was), and I wondered why such a number. Would it...