Creatures the World Forgot (1971)

They don't make them like this anymore... not in a million years!

As the first nomadic tribes wander across the vast wilderness of the infant planet they confront hostilities created by the harsh environment and each other. After a massive volcanic eruption a tribal chief is killed and his two sons fight for supremacy, not only for the leadership of the tribe but also for the love of a beautiful young woman. The age-old battlegrounds of rivalry, envy and passion are explored in this tale of prehistoric adventure.