Edgar Rice Burroughs had dabbled in the lost world genre before he wrote his classic The Land That Time Forgot in 1918. The first film adaptation didn’t occur until 1975 with legendary fantasy writer Michael Moorcock writing the screenplay.
Set during WWI a British boat has been torpedoed by a German u-boat. The survivors manage to get aboard the u-boat and take it over. The Germans manage to sabotage the navigation and the u-boat ends up in the south Atlantic where they come across a lost continent called Caprona.
Once on the island they discover dinosaurs, cavemen and many other dangers. They discover a neanderthal named Ahm. They also discover oil which they try to refine so they can fuel up the u-boat.
The effects are pretty bad. The dinosaurs are all hand puppets instead of the superior stop motion that One Million Years B.C. had. Still the movie is pretty entertaining and vastly superior to the crappy Asylum remake in 2009. You know it’s bad when the hand puppets look better than the crappy CGI.
The movie was a hit for American International and Amicus and a sequel was made, The People That Time Forget and a third Edgar Rice Burroughs adaptation, At the Earth’s Core. All three movies starred Doug McClure.