Originally planned to reinterpret it as a kind of bipedal gorgonopsid, but that felt like too much of a stretch, design-wise
Discovered in 1967 on a remote island off southern Japan, Gorosaurus was originally thought to be a mutated dinosaur, much like Godzilla. However, later research of its cellular structure in comparison to other reptiles (and Godzilla) found that Gorosaurus belonged to a more ancient species of reptile.
Being roughly 40 meters in height as well as being exclusively bipedal, Gorosaurus is very much unlike any other archosauruform known to the fossil record. The intended use of the crooked tail eluded study until one battle with another monster, during which Gorosaurus reared back onto it and kicked with its powerful hind legs.
Giant monsters such as Baragon, Anguirus, and Manda have been theorized to have been mutated individuals of their respective species, though none of them are as drastic departure from their species from as Gorosaurus. Its discovery has caused biologists to re-think the origin of these giant monsters, from random natural mutations to something more mysterious.