But it is indeed necessary to have a real source for human imaginations?
It is interesting to speculate on the artist's inspiration.
Your coin is beautiful. I remember bidding for it. The
ketos on your example has a snout that resembles the creature from the vase. It looks something like a
pig or
dog.
I have attached an image of my
Perseus and Andromeda with
ketos from the same
mint. On my example, and on no other dies that I have seen, the
ketos looks like a dead
fish. Perhaps the artist, not knowing what a sea monster should look like, imagined a large
fish.