A cowboy in a travelling rodeo wants another specimen of his show's latest star attraction - a miniature horse. Aided by a British palaeontologist, he heads into a mysterious forbidden valley, where he is amazed to find ferocious dinosaurs are roaming. Unfortunately, a giant prehistoric monster has them in its sight. Fantasy Western, starring James Franciscus and Gila Golan, with effects by Ray Harryhausen.

A turn of the century wild west show struggling to make a living in Mexico comes into the possession of a tiny prehistoric horse. This leads to an expedition to the Forbidden Valley where they discover living dinosaurs. They capture one and take it back to be put on display, leading to inevitable mayhem.