LINK quote [To begin with, let's get things straight and admit up front that Godzilla is not a real animal, nor was it ever. It's an unfeasibly big late-surviving dinosaur (belonging to the hypothetical taxon Godzillasaurus, according to some), mutated by radiation, with a radioactive heart, and virtually impervious to other gigantic monsters, robots, artillery, laser blasts, lava and fire. Not real. Sorry about that. But by posing questions about fictional entities we can still learn stuff, and you may be surprised to learn that Godzilla has, on occasion, been discussed semi-seriously by various biologists and palaeontologists].