All movies starring Kirby Atkins

Mosley, and his family of four-legged Thoriphants, live a worker's life on an isolated farm owned by Simon - a sullen, and mean-spirited farmer. One evening, after plowing all day, Mosley' discovers a cave with large ancient drawings on the walls - they're of Thoriphants similar to Mosley and Rue except they stand upright. Is this what the Thoriphant race used to be? What happened to cause them to become bent backed creatures without hands?