Quiz

One of the last screen credits for Willis H. O'Brien who was the mastermind behind the special effects for the original King Kong (1933). O'Brien's input was largely restricted to hundreds of conceptual sketches for the dinosaurs. Budget limitations meant that none of them were realized on film.

A common special effect of the era, the dinosaurs were created from iguanas, monitor lizards, and adolescent alligators, with horns, bony hoods, or fins attached.

Scenes from Mondo perduto (1960) were used in the Viaggio in fondo al mare (1964) episode Turn Back the Clock (1964) (October 26, 1964). Actress Vitina Marcus reprised her role as the native girl in that episode.

Director Irwin Allen wanted to use stop-motion dinosaurs for this film, but due to budget reasons he had to use lizards - mainly monitor lizards - as dinosaurs. Plastic horns and spikes were attached to them to make them look more like dinosaurs.

Allen imported six-foot-long monitor lizards from Singapore and paired them with alligators. In one famous sequence, one of the monitor lizards dukes it out with a Cayman alligator so potently, that the American Society for the Prevention of Cruelty to Animals lodged a formal complaint against the Fox studio. The final result performed well at the box office and drew some positive reviews mixed with the negative ones.

David Hedison was reluctant about making the film as he didn't think the material was any good. Seeing Jill St. John dressed in a pink outfit with a poodle on set didn't do much to make him think differently. Nevertheless, he applied himself anyway, to the extent that Irwin Allen offered him the lead in his next film, Viaggio in fondo al mare (1961). Hedison turned it down but would later take a part in Allen's TV series based on the submarine film.