The Siebengebirge came into being about 30 millon years ago. 30 million years .. this age seems beyond human imagination, yet in the context of earth history it is just a moment. Diplodocus, whom you see in the collage above, lived about 155-145 million years ago in the Upper Jurassic. So: no, the dinosaurs came and went before the Seven Mountains came into being.
If you like dinosaurs and you speak German, I’d like to invite you to visit my site
it is situated in the Seven Mountains too.