Voyage to the Prehistoric Planet (1965)

A spaceship orbits the planet Venus, piloted by astronaut Marcia (Faith Domergue). On the surface two fellow astronauts, and a robot companion, set out on a voyage of exploration, observed from afar by Professor Hartman (Basil Rathbone). First they are attacked by prehistoric creatures, and then lose their robot in a massive volcanic eruption that consumes the planet.