From a lost expedition to a plateau in Venezuela, Paula White brings the journal of her father explorer Maple White to the eccentric Professor Challenger in London. The journal features sketches of dinosaurs which is enough proof for Challenger to publicly announce that dinosaurs still walk the earth. Met with ridicule at an academic meeting at the Zoological Hall, Challenger reluctantly accepts a newspaper's offer to finance a mission to rescue Maple White. Professor Challenger, Paula White, sportsman Sir John Roxton, news reporter Edward Malone (who is a friend of Roxton and wishes to go on the expedition to impress his fiancée), a skeptical professor Summerlee, an Indian servant Zambo, and Challenger's butler Austin leave for the plateau.
At their campsite at the base of the plateau, the explorers are shocked when a large rock falls, sent their way by a Dryopithecus perched on top of an overhead ledge. As the crew look up to see their attacker, Challenger spies overhead a Pteranodon (mistakenly calling it a Pterodactylus) killing and eating a young Toxodon which proves that the statements in Maple White's diary are true. Leaving Zambo and Austin at the camp, they cross a chasm onto the plateau by cutting down a tree and using it as a bridge, but it is knocked over by a Brontosaurus, leaving them trapped.
The explorers witness various life-and-death struggles between the prehistoric beasts of the plateau. An Allosaurus attacks an Edmontosaurus, and knocks it into a bog. The Allosaurus then attacks, and is driven off by a Triceratops. Eventually, the Allosaurus makes its way to the campsite and attacks the exploration party. It is finally driven off by Ed who tosses a torch into its mouth. Convinced that the camp isn't safe, Ed climbs a tree to look for a new location, but is attacked by the Dryopithecus. Roxton succeeds in shooting the Dryopithecus, but the creature is merely wounded and escapes before he can finish him off. Meanwhile, an Agathaumas is attacked by the Allosaurus, and gores it to death. Suddenly, a Tyrannosaurus attacks and kills the Agathaumas, along with an unfortunate Pteranodon.
The explorers then make preparations to live on the plateau potentially indefinitely. A catapult is constructed and during a search for Maple White, Roxton finds his remains, confirming his death. It is at this time that Ed confesses his love for Paula and the two are unofficially wed by Summerlee who used to be a minister.
Shortly afterwards, as the paleontologists are observing the Brontosaurus, an Allosaurus attacks it and the Brontosaurus falls off the edge of the plateau, becoming trapped in a mud bank at the base of the plateau. Soon afterwards, a volcano erupts causing a mass stampede among the giant creatures of the lost world. The crew is saved when Paula's pet monkey Jocko climbs up the plateau carrying a rope. The crew use the rope to pull up a rope ladder constructed by Zambo and Austin and then climb down.
As Ed makes his descent, he is again attacked by the ape-man who pulls the rope ladder. The ape-man is again shot and finally killed by Roxton. They discover the Brontosaurus that had been pushed off the plateau had landed softly in the mud of the river, trapped but still alive, and Challenger manages to bring it back to London, as he wants to put it on display as proof of his story.
However, while being unloaded from the ship it escapes and causes havoc until it reaches Tower Bridge, where its massive weight causes a collapse, and it swims down the River Thames. Challenger is morose as the creature leaves. Ed discovers that the love he left in London has married in his absence, allowing him and Paula to be together. Roxton morosely but gallantly hides his love for Paula as Paula and Ed leave together, while two passersby note: "That's Sir John Roxton—sportsman."Sir Arthur Conan Doyle as himself (appears in a frontispiece to the film, missing from some prints)
Bessie Love as Paula White
Lewis Stone as Sir John Roxton
Lloyd Hughes as Edward Malone
Wallace Beery as Professor Challenger
Arthur Hoyt as Professor Summerlee
Alma Bennett as Gladys Hungerford
Virginia Brown Faire as Marquette the half-caste girl (uncredited)
Bull Montana as Ape man/Gomez
Francis Finch-Smiles as Austin
Jules Cowes as Zambo
Margerette McWade as Mrs. Challenger
George Bunny as Colin McArdle
Charles Wellesley as Major Hibbard
Nelson MacDowell as Attorney (uncredited)
Chrispin Martin as Bearer/Cannibal (scenes deleted)
Jocko the Monkey as himself
Mary the Chimpanzee as herself (uncredited)
Agathaumas (seen in battle with Allosaurus and Tyrannosaurus and is based on a hypothetical restoration by Charles R. Knight,)
Allosaurus (main carnivorous dinosaur seen, attacking Trachodon and Triceratops among others)
Ape-man (menaces the team of explorers)
Brachiosaurus (seen during the volcanic eruption, one of which was attacked by a Tyrannosaurus)
Brontosaurus (The main antagonist. After falling into a bog at the conclusion of a fight with an Allosaurus, one is captured and taken to civilization, where it escapes and terrorizes the city)
Edmontosaurus (is preyed upon by the Allosaurus and also called by synonym Trachodon or Anatosaurus)
Pteranodon (the first prehistoric animal seen by the team of explorers)
Stegosaurus (one disturbs the Agathaumas before the fight with the Allosaurus and Tyrannosaurus. It also escaped the volcano eruption)
Toxodon (a juvenile was seen being eaten alive by the Pteranodon. It is the only prehistoric mammal that is not a primate they find on the plateau)
Triceratops (shown to be capable of handling an Allosaurus in battle)
Tyrannosaurus (is seen to have little trouble bringing down Agathaumas, as well as having a taste for any Pteranodon that swoops in too close. One fights with a Brachiosaurus in the eruption scene. Like the film Fantasia it is shown with three fingers.)
Chimpanzee (helps the Ape-man antagonize the explorers)
Caiman or alligator
Jaguar (stock footage)
Spectacled bears (erroneously identified as "Spectacle Cave Bears")
Two-toed sloth (stock footage)
Willis O'Brien had previously, in 1918, worked on a film called The Ghost of Slumber Mountain that used stop motion photography. In The Lost World he combined animated dinosaurs with live-action footage of human beings, but at first he was able to do this only by separating the frame into two parts (also known as split screen). As work went on, O'Brien's technique grew better and he could combine live-action and stop-motion footage in the same part of the screen.
The dinosaurs of this film were based on the artwork of Charles R. Knight. Some of the dinosaur models used in the film came into the famous collection of the fantasy lover Forrest J Ackerman.
This was the first feature-length film made in the United States, possibly the world, to feature model animation as the primary special effect, or stop motion animation in general.
Doyle frequently mentioned that Professor Challenger, not Sherlock Holmes, was his favorite character among his creations.
In 1922, Conan Doyle showed O'Brien's test reel to a meeting of the Society of American Magicians, which included Harry Houdini. The astounded audience watched footage of a Triceratops family, an attack by an Allosaurus and some Stegosaurus footage. Doyle refused to discuss the film's origins. On the next day, the New York Times ran a front page article about it, saying "(Conan Doyle's) monsters of the ancient world, or of the new world which he has discovered in the ether, were extraordinarily lifelike. If fakes, they were masterpieces".
In April 1925, on a London-Paris flight by Imperial Airways, The Lost World became the first film to be shown to airline passengers. As film stock of the era was nitrate and highly flammable, this was a risky undertaking on a wood and fabric-hulled plane, a converted WW1 bomber, the Handley-Page O 400.
This is the first dinosaur-oriented film hit, and it led to other dinosaur films, from King Kong to the Jurassic Park series.
American Film Institute recognitionAFI's 100 Years...100 Thrills – Nominated
AFI's 10 Top 10 – Nominated Fantasy Film
George Eastman House – Laserdisc preservation with stills showing missing scenes
George Eastman House – Film restoration using materials from Czech National Film Archive. Some sequences still missing and some inadvertently left out
David Shepard, Serge Bromberg – DVD version using Kodascope prints, Czech archive materials, and trailers. Like the George Eastman House restoration, some sequences are still missing and some inadvertently left out
Some notes on the various restorations of this film as well as DVD info from Carl Bennett of silentera.com database