The Beast of Hollow Mountain

The Beast of Hollow Mountain is a 1956 Weird West horror film about an American rancher living in Mexico who discovers his missing cattle are being preyed upon by a dinosaur.
Production.
The first film to show dinosaurs and cowboys in the same picture, it is notable for being based on a story idea by special effects innovator Willis O'Brien. O'Brien was also to have originally done the special effects for this movie, but this did not happen for reasons unknown. Jack Rabin, Henry Sharp and Louis de Witt ended up doing the effects, probably based on O'Brien's storyboards. This film was one of the few American/Mexican co-productions of the '50s. It was made in color and filmed in CinemaScope. It starred Guy Madison and Patricia Medina, and was produced/ co-directed by Edward Nassour.
The film was filmed back-to-back in both English and Spanish at Churubusco Studios in Mexico City and released as "La bestia de la montaña" in Mexico.
O'Brien's story that inspired the script for this film also inspired his earlier, unproduced script "The Valley of the Mists", which would later be made as "The Valley of Gwangi" by O'Brien's protégé Ray Harryhausen.
In popular culture.
On April 14, 2017, the film was "riffed" as Episode Five of the new Season Eleven of "Mystery Science Theater 3000" on Netflix.