Alien-filmek (igen, a Promcsi is)

The Xenomorph has been portrayed in noticeably different ways throughout the film series. Much of this was due to the continuing advancements made in the field of special effects, technology, and techniques used to bring it to life.

It has also been shown, both on-screen and in the games based on the Alien series, that the Xenomorph's form is affected by its host, so that different species of hosts will create different varieties of Xenomorph. An example of this is seen in Alien³, when a dog (an ox in the extended edition) spawns a Xenomorph with a distinct canine body structure, quadrupedal movement, and greatly enhanced speed.
Upper BodyEdit

In the original Alien film, and in the sequel Aliens, Xenomorphs are depicted as tall, slender creatures with a roughly human biomechanical design. The chest area appears to be rib cage-like in design.

In later films, such as Alien: Resurrection and Alien vs. Predator, they are depicted as being shorter and bulkier organisms, as well as being more quadrupedal, portrayed by either stuntmen in suits for close-ups, or computer-generated imagery for their full form.

In Aliens, Xenomorphs are depicted as having ridges along their cranium, while in all other films they have smooth cowls covering their skulls. It was speculated in the Aliens bonus DVD that this was due to these Xenomorphs having had more time to mature, compared to the Xenomorphs in the other films.

In the comics and various video games (Aliens vs. Predator: Extinction, Alien vs. Predator (SNES), Aliens vs. Predator 2), this was depicted as one of the visual differences between the Xenomorph Drone and Warrior castes. The Drones (in this instance used to indicate a "worker" caste, instead of mating-capable males) have the smooth cowl while the Warriors display the ridges. The Drones and Warriors have different tasks: warriors defend the hive, and drones hunt potential hosts, while some live only to protect the queen, such as hive warriors or praetorians.

In Alien and Alien³, the Xenomorph has six fingers, with the index and middle fingers conjoined into one digit, ring and little fingers also conjoined, and thumbs on both sides. In Aliens, the Xenomorphs are shown with five fingers, with the second thumb missing. In Alien: Resurrection and Alien vs. Predator, the aliens have four fingers, though the middle two appear to be a fusion of two digits. No explanation is given in the films for the fluctuating number of digits, although the creature's well-known genetic plasticity probably accounts for that.
Lower BodyEdit

In Alien and Aliens, the Xenomorphs were plantigrade. In Alien³, the Xenomorph is digitigrade, owing to its quadrupedal host organism (a dog in the theatrical cut, an ox in the extended version).

Alien: Resurrection saw a dramatic redesign from previously-encountered human-spawned breeds: the Xenomorphs that emerged from human hosts in this film walked on digitigrade hind legs in a manner that does not conform with the appearance of previously-seen members of the breed. This is complicated by the fact that the Xenomorphs of the film were spawned by a Queen grown from cells derived from a clone of Ripley, making their genetic heritage muddled at best.

In Alien vs. Predator, the Xenomorphs return to their roots as plantigrade organisms, though their legs are sleeker and more skeletal in appearance, due to the use of computer visuals and hydraulic puppetry, rather than costumes.

Originally, the Xenomorph's tail was roughly the length of the rest of its body, with a small, almost surgical stinger-like barb on the end; but from Alien³ onwards, the tail has extended in length and features a large, knife-like blade at the tip.

In Alien: Resurrection and Alien vs. Predator, the tails have also supported a ridge of spikes right before the blade. This was introduced in Alien: Resurrection to help them swim convincingly, and was left intact in Alien vs. Predator. The tail itself is shown to be of incredible length during Alien vs Predator, measuring almost its full body length.

The original shooting script for Aliens featured a scene in which Lieutenant Gorman was "stung" by a Xenomorph's stinger. He was not killed, merely stunned, and the barb remained lodged in his shoulder, having torn loose from the Xenomorph's tail much like a bee stinger. The novelization also included this scene, though the final cut of the movie does not. This attribute is used later on in various games.
The HeadEdit

The most notable feature of the Xenomorph species is the elongated, banana-shaped head. This aspect is both disturbing and terrifying, combining visual elements that are usually blocked by our conscious mind with others resembling vaguely human features.

It is widely assumed that it identifies enemies by sensing pheromones. This has never been explicitly confirmed nor denied, but a Drone will not kill a host body already infected (as seen in the movie Alien 3 and the book Aliens: DNA War).

There has been one detail on an alien's head that may be an eye being so small and the same black as the skin. It is hard to see if these are eyes or an implant on the skin (you can see them on the front cover of the Aliens vs Predator 2010 video game and very rarely as a predator in alien vision). Another idea is that their whole head is one big insect-like eye; in Alien 3, a fish-eye lens represented the Runner's sight, but it is unknown if this is really how it sees or simply artistic license.

Other proposed conjectures include that the eyes are similar to a desert-burrowing lizard's eyes; meaning that they lay under a thin layer of skin, yet are deep enough that they are not visible from the outside. This is seemingly lent support by early models and toys of the Warrior Xenomorph while Alien was still the only existing movie in the timeline. These showed an actual, physical, humanoid skull built under the smooth carapace, with the smooth top working like a one-way visor.
Dorsal Spines Edit

Along the back of most Xenomorphs' bodies are a series of appendages that appear to have no function. It's still in debate what they are used for, with theories ranging from sensory organs to communication organs, to breathing apparatus, to defensive mechanisms, to structures that dissipate heat, to storing substances their bodies need, or to provide structures to carry around the young, underdeveloped chestbusters, the eggs or the facehuggers or as a counter weight to keep them from falling over when running. None of these ideas has been confirmed or denied by official sources so far.

One theory is that the four back appendages are used as a type of radar that the alien uses to see through extreme environments or detect movements. However in the extended universe it is said that the dorsal spines are used to secrete and possibly store the resin used to build their hives.

It is interesting to note that, in the Alien vs. Predator Volume 1 comic, Xenomorph Drones bury themselves in the ground, yet their spines are still shown just breaking the surface, implying some use when connected to the environment. This may be either biological (breathing, heat exchange, etc.) or sensory (detecting the vibrations of marines walking on the ground above).

Other hypotheses include:

Perhaps the spines separate the dominant Xenomorphs from the weaker ones, for example, the smaller the spines, the weaker the Xenomorph.
The creatures might come from a mainly amphibious planet, and perhaps the spines are a mechanism to swim underwater faster to catch prey. They do not seem all that hydrodynamic, but it's possible to suppose the spines might be used for stability, like the dorsal fins of a dolphin (not that their shape seems very much efficient at that either).
The spines might be spiracles that take in and filter the air around them, while waste is expelled through the mouth. It is widely accepted that they do not have lungs, so this is possible, and yet implausible because Runners, or Dog Aliens, don't have them. But it may be that the Runners have lungs.
The spines might be used as a defense mechanism, to repel enemies that try to sneak up on them from behind or above.
They might also be traits that the alien acquires by chance when developing inside the facehugger, putting legs of the facehugger on the back. The chestbuster does not develop directly from the facehugger (instead, the facehugger plants the egg/larva that will become the chestbuster inside a host), but it's not impossible that it acquires genetic traits from it.
They might be used to blend in with the hive web when under attack.
The spines may be for Chestbursters to latch onto, allowing the adult to bring them to a safer location.
If the alien uses echolocation to see its prey, these may be what they feel the vibrations from.
They may be used to carry unhatched eggs to a new location when the Queen dies giving them the ability to still climb walls while on the move.
They might be used to create the hive somehow.
The spines may be used to distribute pheromones - to distinguish one from another, and from other hives.
The spines may act much like the Carrier Xenomorph form seen in Alien Vs. Predator: Extinction, allowing a Facehugger to hook their spider-like legs until a victim is near. The Facehugger will let go of its crude form of transportation, find the victim, and proceed with the process of laying eggs.
The spines may also act as a counter balance, much like a cat's tail, so that the Xenomorph does not fall forward when running. Though in truth, a cat does not require a tail to balance properly while running, it more so helps to balance upon thin surfaces like fences and the backs of chairs, so this theory has little credence.

Secondary JawsEdit

The secondary jaws, also known as the inner mouth, double jaw, or maw, is another disturbing feature of the species. It's assumed that it's powered by extremely strong muscles inside the creature's head, that enable it to be quickly launched and retracted, similar to the tongue of a chameleon. (Although the albino xenomorph drone has a very long "inner mouth" that can implant chest busters into its host like the "Predalien".).

It is the Xenomorph's close-combat weapon, as opposed to its long-range tail. The Xenomorph lashes it out of its mouth, and it destroys anything it hits, able to put a hole in a thickened Yautja skull and still have enough power to plunge another hole through the back as it escapes.

The secondary jaw is powered by muscles as seen in the first Alien vs. Predator movie when the predator rubs a part of the interior (resembling the gills of a crab) a feature that can be seen from the external midsection on each side of the head, ovular in shape. Muscles rub along here, letting the mouth be pushed out like a piston through the target the Xenomorph has acquired.

The Predalien has the ability to use its inner mouth to implant Chestburster embryos into a host's throat, like a Facehugger.

Yautja take them as souvenirs of their kill.
The TailEdit

It is accepted that the tail is an offensive weapon and little more. Though the creature can and will run on all four appendages, it often stands on its two hind legs so it can reach for its prey with its arms. While standing, it has also been seen to impale its victim with its tail, even to the point where it can raise a creature heavier than itself to eye level, possibly in preparation for a face-bite using the secondary jaws. This would clearly be impossible if the tail were needed for balance, as the already-shifting weight would be too awkward, causing the monster to fall.

As a weapon, the tail is extremely efficient, as it is long enough to attack from great distance and can be used in a variety of ways; for example, in Alien vs. Predator, a Xenomorph used its tail to knock the legs out from under a Yautja before trying to stab it.

The tail can be used in stealth attacks, since it is flexible enough to attack from a variety of positions, and is hard to notice if it is behind the enemy, or if the area is rather dark. Even when the sharp point is cut off, the tail is still deadly, as the Xenomorph can use the tail to spray its acid blood from the severed tip over a wide area. Xenomorphs are also capable of using their tails as blunt-force weapons, clubbing their enemies with the vicious tail spikes.