Rhedosaurus (Beast from 20,000 Fathoms) Skull

Here's the grandfather of them all. King Kong established the theme of a giant creature attacking a major metropolitan area, but it was the giganitc Rhedosaurus in "The Beast from 20,000 Fathoms" that established the gigantic, radioactive reptilian holdover from the Mesozoic as a standard. He's pretty much the prototype for Gojira, even down to the large canines, dorsal plates, and small ears. Though it was referred to as a dinosaur, it looks more like a gigantic crocodylomorph.
Then again...maybe I'm over-thinking it.