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Monstrous Mandibles

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Mandibles: For when normal jaws just won't get the job done.

1. the jaw or a jawbone, especially the lower jawbone in mammals and fishes.
2. one of a pair of mouthparts of an arthropod, designed for holding food.

As Most Writers Are Human, we're typically most accustomed to dealing with other humans, or at least other vertebrates, and thus anything that deviates too much from that template looks creepy. Even with animals we're used to seeing a two-part, one-on-top-of-the-other jaw system on everything from whales to dogs to birds.note  So adding, say, arthropod-style mouthparts to the jaw system we're used to, or even replacing it entirely, is a quick and easy way to make something seem strange and other.

Monstrous Mandibles in fiction are typically found in four types.

  1. Decorative: This is a simple decorative addition, little more than tertiary nubs or tusks. Expect to see these mainly on Rubber-Forehead Aliens, though artificial designs to helmets and masks to resemble such an appearance also count.
  2. Functional: This is the functional addition. Whether they're little more than a tooth on a joint or a fully articulated limbs, these are mandibles that can actually do something.
  3. Bifurcated: This is the bifurcated jaw. Almost exclusively seen with the lower jaw, this has the existing jaw system fused with the monstrous set up, such that the jaws (or at least lower jaw) actually split in half.
  4. Replacement: This is total replacement, where Monstrous Mandibles are the only mouth parts. These are the default in Insectoid Aliens and more commonly found on particularly strange creatures. Also always the case in Real Life with any arthropod that actually has mandibles.

For creatures where these are almost universal, see Insectoid Aliens, Big Creepy-Crawlies, and Predator Pastiche. Sub-Trope to Monster Mouth.


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    Anime & Manga 
  • In Berserk, Rosine's "children" are tiny humanoids who look like fairies. However, when angry their mouths spit sideways into insectile mandibles, revealing them as wasplike monsters.
  • In Overlord (2012), Cocytus has a set of Functionals that appear to be more for crushing than piercing.

    Comic Books 
  • El Toxico: The Big Creepy-Crawlies overrunning the world tend to have their mouths flanked on both sides by some big sharp teeth.
  • Spider-Man:
    • Man-Spider — Spider-Man's mutated monstrous form — has a pair of chelicerae alongside his now fang-lined jaws.
    • Spider-X (Brian Kornfield) is a vigilante who made a deal with the eldritch god Chthon in exchange for powers similar to Spider-Man's, mutating him into a monstrous creature almost identical in appearance to Man-Spider.
    • The Other — the spider-god who gave Spider-Man his powers — is depicted as a giant spider-monster with both chelicerae and fanged jaws.
    • In Spider-Verse, when Kaine unleashes the Other's full power against the Inheritors, it transforms him into an enormous monster with fanged jaws and four chelicerae.
    • In Savage Spider-Man, the monstrous Spider-Man is depicted as having fanged jaws and four Predator-style mandibles on the cover.

    Fan Works 
  • Abraxas (Hrodvitnon): Monster X in their final form has the Functional type, in the form of two jawbone-like pieces on either side of their actual jaw which can apparently flex.

    Films — Animation 
  • Mister Scroop from Disney's Treasure Planet has a pair of ant-like mandibles added onto a conventional maxilla-and-mandible mouth, qualifying as Decorative. They fit well with his arachnoid body, six walking legs and irisless eyes. They're appropriate for a character who's The Dragon of a cutthroat pirate band.
  • Some of ants in The Ant Bully have Decoratives in order to keep their insectoid appearance while still looking relatively human.

    Films — Live-Action 
  • The Predator in, well, Predator has two sets of Functionals. This carries over to the Predaliens in Alien vs. Predator.
  • These show up with surprising frequency in the Blade Trilogy. The Reapers in Blade II are Bifurcated, while Dracula's true form in Blade: Trinity has multiple sets of Functionals.
  • The Creeper of Jeepers Creepers has Functionals that it typically keeps pressed flat against its face to disguise the inhuman features.
  • The Mega Kaiju in Pacific Rim: Uprising has a set of Functionals in the form of insect mandible-like projections from the lower jaw tipped with nasty-looking tusks.
  • Godzilla: Gigan has two long curved mandibles on either side of his bird-like beak. Averted with the majority of insectoid kaiju in the franchise, who have either normal horizontal mouths (Megaguirus, Kamacuras) or vertical mouths (Mothra, Battra).
  • Shin Godzilla: The titular Kaiju has a serpentine bifurcated jaw that splits open when he uses his Atomic Breath.

  • In The Kane Chronicles, the scorpion goddess has a set of Functionals inside of her human mouth.
  • In Worm, Taylor/Skitter evokes this artificially with her mask, which is designed to resemble the mouthparts of an insect to make her seem more frightening.
  • In the John Carter of Mars series, apts are an unholy combination of abominable snowman and hippo, and among their many horrifying features is a set of mandibles.

    Live-Action TV 
  • In the Doctor Who episode "Utopia", the alien scientist Chantho — an insectoid Rubber-Forehead Alien — has a large set of Decoratives framing a normal human mouth.
  • In The Strain (TV series), the vampires have fleshy mandibles that are typically retracted into their throat but come up into the mouth when they feed. They aren't used to feed themselves but act as a sheathe for the "tongue" the vampires use to drink blood, making them a strange variation on Functionals.
  • Supernatural: Creatures from a parallel universe, called "canids" in the script, introduced in "Wayward Sisters" have mouths of this type. To use the words of the Supernatural wiki, "the canids mouth reveals a mandible that when opened reveals a beak with tendrils."

    Tabletop Games 
  • Warhammer 40,000:
  • Dungeons & Dragons:
    • Depending on the Artist, the gargantuan Purple Worms and their variants sometimes have Functional mandibles, which they use to grab opponents and swallow them whole.
    • Thri-Kreen from Dark Sun have functioning mandibles that they could deliver a bite attack with. If the idea of being bitten by a humanoid preying mantis isn't terrifying enough, their bite also injected a paralytic venom.
    • Umber Hulks are large creatures that resemble a semi-humanoid beetle that stands about eight feet tall. They have huge, serrated mandibles that inflict vicious damage in combat. Oh, and they have a confusion-causing gaze attack.
  • Pathfinder: Astradaemons are evil Outsiders who look vaguely like tentacular, anthropomorphic deep-sea fish with a set of Functionals. Not only does it add to their eerie appearance, it also helps them indulge in their favourite pastime of Soul Eating.
  • Shadowrun has Insect Spirits, which can possess humans and turn them into human-insect hybrids. Large, biting mandibles are a common trait, especially if it's something like a beetle, dragonfly, or ant spirit doing the possessing. Metahumans may also grow insectile mandibles as a result of experiencing a SURGE event. Due to their unfortunate resemblance to Insect Spirits, this tends to result in them having a life expectancy that can be measured in minutes once someone else finds out.

  • The Transformers G1 had Repugnus, an Autobot who's alt-mode was a sort of bug-monster with both normal jaws and functioning mandibles. As a gimmick on the toy, a button on his monster mode's head could be pressed, causing his mandibles to open and close and cold sparks to shoot from his mouth.

    Video Games 
  • The mutations of the necromorphs in Dead Space usually cause their lower jaws to split into Bifurcated.
  • Divinity: Original Sin II: The Lamenting Abomination looks like a grotesque Shapeshifter Mashup whose mouth is composed of the upper jaws of at least five wolves, stitched haphazardly together.
  • The volatiles from Dying Light
  • All of the monsters in Evolve have some kind or another. The Goliath and Gorgon both have Functional, while the other three all have Bifurcated.
  • The Elites/Sangheili in Halo have two sets of jaws. Depending on how one looks at it, it could either be two sets of Bifurcated, two of Functional, or one set of each. Expanded universe materials make clear that they have trouble pronouncing phonemes in human languages because of them (and conversely, humans have trouble speaking their language).
  • The turians in Mass Effect are covered in bony plates which form beak-like protrusions, bony heel spurs, and spiky crests as well as Functional mouthparts on either side of their jaws, giving them beak-like points in place of lips, needle-like fangs, and insect-like mandibles. In spite of this, they're possibly the alien species with which humans actually have the most in common.
  • The final boss of Mass Effect 2 has two sets of what would be considered Functionals if it wasn't a machine.
  • The eponymous metroids of Metroid have Replacements, with one set used to hold onto prey and another set for the actual life-drinking.
  • Starcraft II:
    • Larger zerg, particularily hydralisks, in have a hybrid between Functional and Bifurcated, with an outer set of jaws splitting apart.
    • The Protoss Dark Templar has different portraits, one of them wearing a pair of Zerg mandibles on either side of his face that gives him a Predator-like look.
  • In Subnautica, Reaper Leviathans are eel/shark Sea Monsters with two sets of wicked mandibles around their toothy mouths. Said mandibles are fully functional and capable of, say, grabbing your Seamoth mini-submarine and slowly crushing it like a tin can, while the Reaper looks you in the eye through the viewport and roars in your face.

    Web Animation 
  • TP: The toilet's upper lip is shown as two separate halves, it being made up of a toilet seat and all.

  • In Earthsong, The Spinster is an anthropomorphic spider-like alien who reveals a set of mandibles to accompany his fanged mouth on the rare occasions he shows his face. The implicit threat of doing so is part of why his species usually wears veils.
  • El Goonish Shive: Sirleck's jaws sort of... wrap around a human head, given that he's a body-hopping eldritch abomination parasite.
  • In Grrl Power, a minor character named Chorius has a set of Decorative.
  • In Kill Six Billion Demons, the dragon-like demiurge Mammon has a Bifurcated for both his upper and lower jaws, though he typically keeps them held together to resemble a more traditional muzzle.
  • Rusty and Co.: An ant-folk Hive Queen who was corrupted by an Artifact of Doom wears a concealing scarf when she's feigning affability, but takes it off to reveal jagged mouthparts with large mandibles when she gives the order for a character to be killed. Her subordinates only have small mandibles or none at all.
  • In Unsounded, the Snake Person Ruck has a set of Functionals on his lower jaw, as well as a pair of small arms growing from back by his ears that seem to serve a similar purpose. He's also an ancient monster who melts minds and drinks thoughts, so they're far from his most inhuman trait.

    Western Animation 
  • The Insecticons in Transformers: Prime have mandibles that are technically Functional, but since they don't actually eat they work more like Decoratives. Either way, it emphasizes their primal, animalistic nature compared to the more mechanical Decepticon Mooks.
  • Admiral Trench from Star Wars: The Clone Wars is an insectoid alien commanding a Separatist battalion of Mecha Mooks. He has two large chelicerae at the sides of a fairly regular mouth that speaks articulately, though punctuated with Verbal Tic clicking. These chelicerae seem to be Decorative, as Trench is never seen using them.

    Real Life 
  • Many snakes actually have a Bifurcated type with their lower jaw, though the connective tissue of their mouth means it looks like one piece until you see the skeleton. Many monitor lizards have the same arrangement. In both cases, this allows the animal to stretch their jaws wide in order to swallow large prey.
  • Chaetognaths have the Functional type, using their mandibles to help catch prey (and even inject venom in some species). They use a muscular “hood” to keep prey from escaping, hence why they don’t fall under the Replacement category.