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Xenomorph Mouth: A Guide To Alien Teeth And Jaws

By | Published January 22, 2024

The Xenomorph is known for its iconic mouth designed by HR Giger, featuring the terrifying inner jaw. This guide explores the intricate details of the Xenomorph's jaws and teeth, providing insight into their biological functions and their role in the creature's predatory behavior. Find out which Xenomorph has the longest inner jaw, and why some Xenomorphs are missing an inner jaw at all.

The Outer Jaws

The outer jaw of the Nostromo Xenomorph

The primary, or outer jaws of a Xenomorph are a formidable feature. Lined with rows of razor-sharp teeth, these jaws are capable of tearing through metal and bone. The strength and resilience of these teeth suggest a highly evolved predatory mechanism, designed for maximum efficiency in hunting and combat. The outer jaws are covered with lips and the sides of the jaws have holes, revealing its innards when the mouth is open. In their default state, the outer jaws are closed, but open when the creature is agitated.

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The Inner Jaws

The inner jaw of the Nostromo Xenomorph

Arguably the most iconic feature of the Xenomorph anatomy is its secondary, or inner jaws. This set of pharyngeal jaws can shoot forward with lethal speed and force, delivering a fatal blow to its prey (called the head bite). The head bite is strong that it can punch through an armored Predator bio-mask. This mechanism is similar to that of Earth's moray eels but exhibits a far greater degree of power and precision. However, the inner jaw is not rigid and is shown to be flaccid when removed from a dead creature. The Predators often take the inner jaw as a trophy as a sign of a successful kill.

Xenomorph Teeth

The teeth of the Xenomorph on the dropship in Aliens

Beyond the structural complexity of their jaws, the teeth of a Xenomorph deserve special attention. Unlike typical predatory teeth seen in Earth's fauna, Xenomorph teeth have a unique composition and structure that contribute to their efficiency as a lethal tool. The teeth are not only incredibly sharp but also remarkably resilient, showing little wear even after penetrating tough materials. No Xenomorph from the movies or Expanded Universe is ever shown to lose a tooth, confirming the Aliens to be "perfect creatures", at least in terms of dental structure. The Xenomorph teeth are usually metallic grey on Xenomorph Warriors, and longer and translucent on Xenomorph Queens.

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Saliva Secretion

The Alien Queen from Alien vs. Predator secrets saliva

The saliva of a Xenomorph is not just a biological byproduct but plays a somewhat mysterious role in its hunting and feeding habits. The viscous nature of the saliva can be seen dripping in large amounts from the creature's jaws, adding to its menacing appearance. The Xenomorph saliva possibly helps with hive building and with sticking potential hosts to the walls. However, the saliva is not acidic as one might assume, and does not hurt on contact. The biggest amount of saliva was secreted from the cloned Xenomorphs in Alien: Resurrection, possibly due to their tampering with Ellen Ripley's DNA.

Xenomorph Acid Spit

The Alien: Resurrection Xenomorph Warrior spits acid

Beyond their formidable jaws, some Xenomorphs exhibit the ability to spit acid. This acid, similar in composition to their blood, is a defensive mechanism, capable of causing severe damage to attackers and obstacles. The facehuggers, chestbursters, and adult Warriors (from Alien: Resurrection) have been shown to spit acid, but only in rare circumstances. The acid reservoirs inside their neck (or head) need to be refilled, taking some time. The Aliens also have a specialized caste for this role, the Xenomorph Spitter, appearing in several Aliens-themed video games.

The Daecon's Jaw

The pink inner jaw of the Deacon from Prometheus

The Deacon, a preliminary variant of the Xenomorph introduced in "Prometheus," presents a unique jaw structure. Its elongated skull and jawline differ significantly from the classic Xenomorph, showcasing the evolutionary diversity within this related species. The Deacon did not have the icon metallic teeth of a Xenomorph, but somewhat disturbing white and human-like teeth instead. This pink jaw lacked teeth at the front but had some white teeth underneath. Other Xenomorphs that include a pink human-like tongue include the Newborn, and the Albino Drone that was cut from Aliens.

The Xenomorph With The Longest Inner Jaw

The Titan Xenomorph and its long jaw from Aliens: Dark Descent

Among the various Xenomorph types, some exhibit particularly elongated inner jaws, including the Alien Queen. However, the longest inner jaw belongs to the Titan Xenomorph, seen in Alien: Dark Descent. This giant Xenomorph inherited its unique trait from its host, a sentient being called the "Ancient Citizen", which was very similar to the ancient Space Jockeys seen in older Alien lore. While the Engineers from Prometheus had a humanoid appearance, the "Ancient Citizen" made a callback to the elephant-like original Space Jockey. A Xenomorph with a trunk (a Space Jockey Xenomorph) also shows up in the Aliens: Infestation video game.

Xenomorphs Without Inner Jaws

A Xenomorph lacking an inner jaw on the cover of Alien - The Original Years

Not all Xenomorphs possess the iconic inner jaws. Certain variations of the species, either due to evolutionary divergence or specific environmental adaptations, lack this feature, relying solely on their outer jaws for predation. For example, the Neomorphs from Alien: Covenant and some Predaliens don't have an inner mouth at all. The Xenomorph can also lose an inner mouth in battle, but probably won't live very long without it, dying from the blood loss. Interestingly, the Xenomorph from the cover of "Aliens - The Original Years Omnibus" is missing an inner mouth, possibly due to the error of artist Greg Land. Greg Land is often accused of plagiarism and notoriously stole artwork from Tristan Jones, but somehow omitted an inner mouth.

Using The Mouth For Eating

The Runner Xenomorph from Alien 3 feeding on a Fury 161 prisoner

Another function of the Xenomorph's mouth, including both sets of jaws, is for the consumption of food. The Xenomorph feeding behavior, while not often depicted in detail, is integral to their survival, utilizing their powerful jaws to consume and process their prey. The Xenomorph runner from Alien 3 is briefly seen feeding on a prison in the hallways of Fury 161, viciously tearing into the flesh. It is not known if the food is swallowed by the smaller inner mouth, or goes around it, into the bigger mouth. The Xenomorphs are shown to have guts in Alien: Resurrection, so the food will end up there later.

Talking Xenomorphs

A talking Xenomorph hybrid from Batman/Aliens II

While Xenomorphs are typically characterized by their silence, certain expanded universe narratives have toyed with the idea of them possessing vocal abilities. The regular Xenomorphs don't talk, but several Alien hybrids have been shown to do so, having human-like vocal cords inside their mouths. The notable Xenomorphs who talked include the White Hybrid King and Trophy Hatchling from Aliens vs. Predator: Deadliest of the Species, and the Arkham Asylum Xenomorph hybrids from Batman/Aliens II. The Newborn from Alien: Resurrection was also more vocal than other Xenomorphs, but did not utter any specific words.


In conclusion, the mouth and teeth of the Xenomorph species are not just a hallmark of their fearsome appearance, but also a testament to their evolutionary perfection as apex predators. From the dual jaws to the uniquely structured and composed teeth, each aspect of their oral anatomy has been refined to ensure maximum efficiency in predation. The variability seen in different Xenomorph types further illustrates the adaptability and diversity of this species across various environments.

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