The Beast Of Hollow Mountain (1956)

Starring Guy Madison, Patricia Medina, Carlos Rivas, Mario Navarro, Pascual Garcia Pena
Directed by Edward Nassour & Ismael Rodriguez
(actor & director credits courtesy IMDB.com)

A cattle ranch owner in Mexico suspects a rival rancher when some of his cattle go missing, but a prehistoric creature is the real menace responsible.

A conventional western for the most part before revealing its sci-fi twist in the form of a stop-motion animated dinosaur, I found this film to be pretty entertaining, well-abetted by a cast of skilled Mexican character actors, who build audience empathy with their plights.  American import Madison isn't given too much to do, but looks good on a horse and brings the requisite toughness to a knock-down drag out fight.  As for the dinosaur animation, it's pretty well-done, despite movement by the beast's tongue that borders on the silly.  Don't expect anything too profound, and you'll have a good time watching this.