Villain Overview
The Sea's Master-Beast of the Ages–raging up from the bottom of time!
~ Tagline
They couldn't believe their eyes! They couldn't escape the terror! And neither will you!
~ Tagline

The Rhedosaurus is the main antagonist of the 1953 black-and-white science fiction monster film The Beast from 20,000 Fathoms.

It's a 100 million-year-old, 200-foot long, 500-ton giant man-eating monster and one of the last surviving members of its species, awakened during hibernation by a nuclear test in the Arctic. It made its way down the North American coast, destroying everything in its path and ending up in New York, its original home. Attempts to kill it were complicated by an ancient disease it carried; spilling its blood freed the virus, which was almost as deadly as the reptile itself.

It served as one of the main inspirations for Godzilla alongside King Kong (who also influenced Rhedosaurus) and is one of the most iconic movie monsters of all time along with them.


The Rhedosaurus on the surface looks little more than a lizard with large fangs, claws and spikes going from the top of its head that run down its back and end on its tail, but originally, it was supposed to be more sauropod-like, resembling the early 20th century depictions of aquatic sauropods (though still with the fangs, claws and spikes, as well as webbed feet and a crocodile-like tail), but was changed into a more unique design, since sauropods (and dinosaurs in general) were common movie monsters around this time.

At one point during its concept art stage, the Rhedosaurus was meant to have horns, but these aren't in the final design for some reason.


The world's been here for millions of years. Man's been walking upright for a comparatively short time. Mentally we're still crawling.
~ Professor Tom Nesbitt regarding the creature's age.
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The Rhedosaurus awakens in the Arctic.

The Rhedosaurus is the scientific name given to a carnivorous dinosaur that was frozen in ice in the Arctic during the Ice Age, where it had been held in suspended animation for millions of years. The last surviving member of its species, it was only released from its hibernated state when it was thawed by an atomic bomb test in the Arctic Circle. Making its way alongside the East Coast of North America towards its original home, where New York City is located, the Rhedosaurus destroys everything that stands in its path.

It sinks a fishing ketch off the Grand Banks, destroys another near Marquette, Canada, wrecks a lighthouse in Maine, and destroys buildings in Massachusetts. Its enemies, the soldiers who attempted to kill it were complicated, because of the ancient disease it carried; spilling its blood that can make people sick and die with an ill feeling while the plague from its blood has freed, which was almost as deadly as a dangerous venomous creature itself. It bleeds all over the streets of New York, unleashing a horrible, virulent prehistoric contagion, which begins to infect the populace, causing even more fatalities. The infection precludes blowing it up or even setting it ablaze, lest the contagion spread further. It is then decided to shoot a radioactive isotope into the Rhedosaurus' neck wound with hopes of burning it from the inside, killing it without releasing the contagion.

When it comes ashore and reaches Coney Island's amusement park, the military sharpshooter by the name of Corporal Stone takes a rifle grenade loaded with a potent radioactive isotope and climbs on board a roller coaster. Riding the roller coaster to the top of the tracks to get eye-level with the beast, he fires the isotope into its open neck wound. The beast thrashes about in pain, causing the roller coaster to spark when it collapses to the ground, setting the amusement park completely ablaze. Letting out one last roar, the Rhedosaurus perishes from the poisoning and heat.

Powers and Abilities

This is full-scale war against a terrible enemy... such as modern man has never before faced. Ordinary bullets have no effect... and a method of destroying the awesome creature... has not yet been formulated.
~ Radio Operator

The creature demonstrates its power.

The Rhedosaurus is a massive and mighty creature, able to destroy buildings with ease and take just about anything the military throws at it. However, shooting the dinosaur with the deadliest weapons will only worsen matters due to the disease in its bloodstream. A single drop of the monster's blood can infect and hospitalize 50 nearby soldiers, touching it may cause death and since the germs in the blood can spread in the air, attacking the Rhedosaurus with flamethrowers or destroying the creature completely could lead to catastrophic events.

If a weapon manages to damage it, the Rhedosaurus possesses a healing factor capable of regenerating small wounds in a matter of hours.


~ The tagline for The Beast from 20,000 Fathoms.
For some reason the creation was called a rhedosaurus, and although I can't remember where this name came from, I suspect Hal Chester or one of the writers coined it. Over the years, people have suggested that the first two letters relate to the initials of a certain animator. I have no comment.
~ Ray Harryhausen, animator of the Rhedosaurus and countless other movie monsters, on the creature's name.
The task of instilling pathos into a creature that was, after all, an innocent victim of circumstances was something I had set myself from the outset, although I was restrained by the script... The Beast is a poor lost soul brought back to life by man and then destroyed by man. If it sounds familiar, it is. King Kong was a huge influence, as he would be in all the other creatures I would be father to.
~ Ray Harryhausen on the creature's circumstances and creation.


  • The scene where the Rhedosaurus destroys a lighthouse was based on the 1951 short story The Fog Horn (retitled into The Beast from 20.000 Fathoms after the film was published as a tie-in) by the late Ray Bradbury.
  • In the few hours the Rhedosaurus' rampage took place, it killed 180 people and injured 1500, causing so much destruction that 300 million dollars would be required to repair it all.
  • The Rhedosaurus makes a cameo appearance in the 6th episode of the 2nd season of ABC's Whose Line Is It Anyway?.
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