They also bleed extremely acidic fluid which is yellowish green in color and often referred to as 'blood', although whether it's used to transport nutrients through the body and/or serves other functions is not clear. This mouth is somewhat similar to the pharyngeal jaw of a moray eel. Little is known about their biology, but it is known that they eat with their 'tongue mouths', not their outer mouths. The typical Xenomorph starts life as an egg-like creature which, when detecting the presence of a potential host, opens up to release the second stage: a small quasi-arachnoid life form which launches itself onto the host's face and impregnates it with an endoparasitoid larva, which later consumes the host from within and exits the body as a vaguely worm-like organism called Chestburster, which then grows very quickly, developing into the adult Xenomorph.ДЄlthough several varieties exist, the adult Xenomorphs all tend to share some common traits: a vertebrate-like body, a protective exoskeleton, a long flexible tail, an elongated eyeless head, and a toothed maw which hides a retractable inner mouth. The Xenomorph physical form varies wildly depending on its life stage, hive caste, age and host, with numerous genetic varieties existing whose origins are completely unknown, as well as varieties which have been genetically engineered by other species. Ridley Scott states during the Director's Commentary on the Alien Special Edition DVD that the eggs are the cargo of the Space Jockey's ship with the ship being a sort-of war ship designed to carry these biological weapons, or perhaps a science vessel carrying the eggs as cargo for scientific study. One idea though, is that they were created by the Mala'kak as biological weapons against an unknown threat or a weapon to wipe out humanity, and the eggs at the derelict ship found at LV-426 was in fact a biological weapon that turned against the crew. Without their native ecosystem to keep them in check they have since run rampant. This theory has been twisted slightly by Prometheus, as they created an artificial subspecies, the 'Deacon' or proto-alien.ДЄnother theory touched on in the expanded universe is they were the alpha predator of their own ecosystem on a nightmarish and harsh planet, but were spread throughout the universe as a food source and a delicacy to a species with a natural immunity to their acidic blood. The Xenomorph could be the result of genetic manipulation by Mala'kak (also known as the 'Engineers' or 'Space Jockeys') as a terraforming mechanism about ten million years ago, but apparently it went horribly wrong. Based on the limited information we have, the most commonly accepted hypothesis is that they are an artificially created species, although another hypothesis says that they evolved naturally on a planet much different than our own.

There are no solid facts as to the origins of the Xenomorph species instead, there are many assumptions which can not be confirmed. The term Xenomorph is derived from the Greek words xeno ('stranger', 'alien', and 'foreigner') and morphe ('form', 'shape'). The Queen of the species is generally twice as large and possesses superior speed, strength and intelligence. The human phenotype is generally around 7вЂ“8 feet, and roughly 136.0 to 181.4 kilograms with a long, muscular tail and large, curved, oblong head. The appearance of the Xenomorph varies depending on its host.

One of the most deadly of all known alien species, these creatures need a host organism in order to reproduce.

The Xenomorph (Latin, Internecivus raptus, 'murderous, deadly' and 'seized'), better known as the Alien, are an extraterrestrial, endoparasitoid species with multiple life cycles, possibly originating from the planet Proteus (also known as Xenomorph Prime). A survivor.unclouded by conscience, remorse, or delusions of morality.' It's structural perfection is matched only by its unmatched hostility.

Xenomorph vs xenomorph avp extinction