This Irwin Allen produced version of the Arthur Conan Doyle novel is one of my favorites. Professor Challenger (Claude Rains), recently returned from a hidden plateau in the Amazon, insists he has seen a dinosaur. A newspaper fronts up money but he has to take a news reporter and the paper's two kids, a rich woman in pink (and her dog) and her younger brother. There's also a famous hunter, Lord John Roxton (Michael Rennie of Day the Earth Stood Still) and an angry helicopter pilot, Manuel Gomez (Fernando Lamas).
Soon after they land on the plateau their helicopter is smashed by a dinosaur. Now,they have to somehow make their way down to safety. They encounter man-eating plants and a giant spider and finally meet a native woman, who likes the youngest guy.
They are eventually captured by her tribe and taken deep within the plateau, which turns out to be an active volcano. Before they are to be sacrificed to their fire god they escape--but there are more dinosaurs to get past. And not everyone makes it out.
Although the dinosaurs are lizards and crocodiles with fins and horns glued to them, it works, as do most of the miniatures. I remember that some of the footage from this movie was used in an episode of Voyage to the Bottom of the Sea, which also featured actor David Hedison (the original The Fly).