I am not contesting the existance of that page, nor do I believe there shouldn't be a Mandarin goby or a cuttlefish (though the latter is far from the top of my wishlist).
As for the originality quaestion, you're missing the point. In real life you don't need to question if it's real or not. Unless you're seeing dinosaurs like in Jurassic Park or something like that, you don't have to think it's impossible. If you can see it it's real. In a SS like this nothing is impossible. Fish could start swimming backwards, morph into a different species or whatnot. If Jim was to create a creature that looked or behaved supernaturally (even if it actually was realistic) the illusion of reality would be lost as people would think it was made up. We had this discussion a long while back when there was talk aboutthe small octopus which mimicked other animals as a defense strategy and if I recall correctly Jim said somethng about if he made a computer generated sky, the clouds absolutely couldn't remind you of anything (though real clouds sometimes do) as everybody would think it was made like that intentionally.
Tiny Realism First
P.S.
Just to make sure here: The level of "supernaturalness" I'm talking of isn't along the lines of cuttlefish, gobys or starfish. Very few people see starfish and immediately say "that creature can't be for real". Having a octopus mimick a crab or a flounder would do that just like some of those scorpionfish which look exactly like a rock. People would just think Jim had put it in as a joke regardless of that the real thing can blend in almost perfectly.
Edit: Looks like Jim beat me to it.