Proto-Xenomorph

The Proto-Xenomorph (fan name) is a creature seen emerging from the dead body of a Mala'kak. It bears many resemblances to a Xenomorph. However, it possesses more human-like teeth and has an erect bipedal posture. It's head shape is also unlike that of other Xenomorphs.

The egg which produced it is believed to have been injected by the tentacled creature, tentatively referred to as a Trilobite by fans.

The Proto-Xenomorph does have resemblences to the Xenomorph: it's head is elongated but ends in a point. It lacks a tail but instead of a mouth-like tongue, it literally has another mouth within it's first one. However, it does resemble the Xenomorph by it's reptilian/insect-like appearence and exoskeleton. It also stands on two legs like the Xenomorph can. The Proto-Xenomorph is born fully-grown (possibly fully grown). It is not born as a worm-like creature but born into it's Xenomorph-like form. It completely bursts from the Space Jockey, not just from it's chest, but it's entire front side.

Nothing else is shown of this Proto-Xenomorph. As of now we can only speculate it is an early stage of Xenomorph that undergoes evolutionary changes to become the recognizable parisitic alien shown in the AVP universe.

As for the Trilobite, it is first shown as a fetus in Shaw's womb. Therefore, it is given birth to by a human, but is surgically removed before full growth and development. After Shaw leaves, she returns to see although she removed the creature from her body it still grew to be a giant mutant-like creature. It has multiple legs and coloring that resembles a Facehugger. The Trilobite soon infects the Space Jockey with a tube-like organ that injects an egg/fetus through the Jockey's mouth. This is also behavior of a Facehugger. It even dies after infection like a Facehugger.

Again, with the Trilobite we can only speculate it is a early generagtion that is perfected by the Xenomorph evolution so that it is smaller and is born from a egg that is produced by a Queen Xenomorph. Remember though that the proto-xenomorph appears 91 years after a classic queen appeared in the Antarctic temple created by the predators human slaves in early BC history. So the queen was released from stasis in 2003 was actually hundreds of years old. This making the proto-xenomorph in Prometheous just a mutant of the species similar to the predalien(AVP-Requiem) or the bull alien (Alien 3). Also note the proto-alien is on planetoid lv-226 not lv-426.