Do you mean the dragon in the background? Fwiw dinosaur fossils have been found for thousands of years already, with theories being that the Cyclops was based on mammoth skulls and griffins on triceratops fossils.
The mammoth-cyclops/griffin-triceratops connection sounded really cool, so I did some quick searches. For what it's worth, it seems that this is a pop theory but not based in evidence.
That is clearly a dinosaur, but almost certainly an avian dinosaur, which aren't particularly hard to find, either in Christian religious art or, for that matter, daily life in much of the world.
