The only thing really keeping Irwin Allen's The Lost World ('60) from being an enjoyably schlocky dino-adventure film is the implementation of a special effects technique dubbed "slurpasaur".
The term (apparently coined by fans of classic creature features like The Lost World) refers to the use of lizards and small crocodiles optically enlarged into the film to pass off as giant, exotic creatures, usually dinosaurs. This process is obviously much cheaper than using models or stop-motion animation, but the effect is generally highly unconvincing and unimaginative.
It's a shame, because for the most part, The Lost World is a fun, stupid, neatly-shot and designed jungle expedition-and-escape B-movie. Claude Rains plays the lead scientist while Michael Rennie (The Day the Earth Stood Still) struts around mysteriously and stoically as Jill St. John stands in as the token hot chick.
The centerpiece action scene taking advantage of the "slurpasaur" technique is a fight between what appears to be a small crocodile and a comparatively-sized iguana, their pinned-on horns and scales flapping around as they go at it.
Among the unintentionally funny moments is the final scene in which Claude Rains' Professor Challenger drops a dinosaur egg (which is initially revealed to be empty) and pulls out a pint-sized lizard, proclaiming, "It's a Tyrannosaurus Rex!" A perfectly inane way to end this gleefully inane film.