Genre-mashes are all the rage nowadays, so a cannibal Western should come as no surprise, especially since we’ve already had “Cowboys & Aliens.” The surprise is that “Bone Tomahawk,” while overlong and awfully leisurely (as well as remarkably gory in its latter stages), is quite enjoyable, rather like a version of “The Hills Have Eyes” transplanted to the old West and enriched by a strong cast and a good deal of flavorful, if often digressive, dialogue.

The script by S. Craig Zahler begins with two bickering ne’er-do-wells Buddy (Sid Haig) and Purvis (David Arquette), who specialize in killing and robbing desert travelers, stumbling onto what appears to be an Indian burial ground and arousing its keepers. Buddy is killed but Purvis escapes to make his way into the inaccurately-named town of Bright Hope. There he’s quickly arrested by Sheriff Franklin Hunt (Kurt Russell) and his jittery old “reserve deputy” Chicory (Richard Jenkins) as he tries to score a drink at the local saloon, the Learned Goat, run by barkeep Clarence (Fred Melamed). Soon he’s ensconced in the jail, where he’s tended to overnight by the town nurse Samantha O’Dwyer (Lili Simmons) and guarded by the regular deputy Nick (Evan Jonigkeit).

Unfortunately all are abducted, and a black stable boy brutally killed, by the cemetery’s keepers, who—according to knowledgeable Indian called The Professor (Zach McClarnon), are a group of inbred, flesh-eating cave-dwellers that he calls the Troglodytes. Hunt gets together a rescue party consisting of himself, the insistent, voluble Chicory, Samantha’s husband Arthur (Patrick Wilson) and white-suited gunslinger John Brooder (Matthew Fox). Together they ride off into the wasteland.

Much of the remaining running-time of the movie is devoted to their journey, first on their steeds and then—after the horses are stolen—on foot (a particularly tough chore for Arthur, who has a broken leg). Zahler provides them with some saucy conversation along the way, with Jenkins in particular relishing the long, theatrical monologues he’s provided with. (By contrast, Russell’s ornate but pithy remarks are like spoofs of gruff John Wayne-isms, while Fox spouts snooty put-downs and Wilson engages in angry tirades.) Eventually Hunt, Chicory and Brooder reach the caves and dispose of a considerable number of attackers, only to fall ultimately into the hands of the Troglodytes; they’re imprisoned along with Samantha and Nick, though the latter is soon disposed of in a particularly gruesome fashion.

The last act of “Bone Tomahawk” is a long bloodletting as their captors, painted in white and communicating with one another via animalistic howls, threaten the prisoners with a fate worse than death. They in turn try to poison the creatures. Fortunately O’Dwyer arrives, guns blazing, to save his wife, and there’s a final grisly confrontation.

The picture does tend to mosey along, especially in the protracted journey to the caves, which explains a running-time well over two hours. But Zahler’s writing is so amusingly over-the-top, and so niftily delivered by the game cast (with Jenkins in particular stealing scene after scene) that things, as edited by Fred Raskin and Greg D’Auria, don’t often drag. After roughly 105 minutes of relatively low-burning action (apart from the brief death scenes of Buddy and the stable boy), the turn to sheer horror in the final thirty minutes or so is rather jarring, and some will find it too much to stomach; it’s like stumbling into Mel Gibson’s “Apocalypto” squared.

The picture benefits enormously from the widescreen camerawork of Benji Bakshi (though the fact that Zahler has also worked as a cinematographer suggests that he had considerable input in that department as well) and from the sparsely-used but moody score by Zahler and Jeff Herriott, which culminates in a closing-credits song that parodies the sort of tune that regularly appeared in 1950s horse operas. Freddy Waff’s production design and Chantal Filson’s costumes also provide some witty details. One might wonder whether Pete Sussi’s special effects included Russell’s prodigious moustache.

“Bone Tomahawk” is obviously an idiosyncratic hybrid that won’t appeal to all tastes, but for those in the mood for something different, Bright Hope might be worth a visit.