from 1000 Misspent Hours:
it isn’t necessary to dig below the surface to appreciate The Beast from 20,000 Fathoms, which works perfectly well as a straight-up monster flick. Technically speaking, this is one of the four or five best-made movies of its type that I’ve seen.and closes by saying this:
the animation of the Rhedosaurus is some of the smoothest ever filmed, making it by far the most believable of all Harryhausen’s frankly fantastic creations (by which I mean to exclude such things as the giant crab in Mysterious Island and the chess-playing baboon in Sinbad and the Eye of the Tiger). Beyond that, the design of the monster has an elegance— even beauty— about it that has rarely been equaled since; apart from its excessive size (it looks to be about 150 feet long from snout to tail), the Rhedosaurus has the appearance of an animal that might really have lived at some point during the Earth’s prehistory. Even if the nuclear angle hadn’t made it the first representative of an idea whose time had come, The Beast from 20,000 Fathoms probably would have spawned imitators solely on the strength of its own inherent quality.