Badlands

An unnamed bounty hunter is hired to collect the bounties of the outlaw Ramsy Brothers when everything goes awry and he must set a trap for them near the Rocky Mountains. They accidentally break through a wall into a massive cavern where dinosaurs still roam. Before the Bounty Hunter can gather his thoughts, he's in an intense game of cat and mouse as the gunslinger tries to capture the brothers and claim the bounty while fighting off ravenous dinosaurs with only his revolvers.