Edison Marshall’s Dian of the Lost Land is a “lost world” fantasy novel following in the tradition of many older novels, the most famous of which is probably The Land That Time Forgot, by Edgar Rice Burroughs. More recent examples include The Lost Ones (1961), by Ian Cameron, which was filmed in 1968 by Walt Disney as Island at the Top of the World, and Lin Carter’s “Zanthodon” series. But there are many, many others.