Random speculation but a couple things stood out for me about the other creatures which are yet to be seen or fully examined yet in any detail whether it be there physiology or their behavior.
1.) That one the creatures seems to gestate rapidly which is also a trait of the Xenomorph embryo. Whatever happens to Shaw, the pregnancy doesn't last for 9 months, that's for damn sure, and more than likely follows a similar gestation time to that of the aliens we all know and love.
2.) Some kind of acid or caustic, acid-like substance burns one of the crews helmet based on what we see in an earlier trailer. Now the connection to that is that we know the aliens have acid for blood of course.
3.) That "squid" thing appears to have tentacles, and I take it, it has to do something with those damn things. So even if it doesn't lay an embryo in someone, perhaps it still latches onto a hosts/prey's face with them.
So what I'm getting at/wondering if that it seems to me that the aliens have a mix of traits from some of these creatures in prometheus. Now unless it turns out that each of these things seperately, all have acid for blood and some variant of the face hugger corresponding to their own species, it would seem that the aliens have an origin related to the union of the dna of these creatures whether on purpose or by accident.
This once again, is wild speculation, but perhaps the human hosts acting as point of intersection between the various creatures and their reproductive cycles, then mixed with a jockey, or even an android, is what ends up producing the aliens. I mean, it would work this way. The first creature infects the host, getting under the skin etc. and somehow infecting the reproductive cells of the host, replacing the host's cells with those of its own(much like hiv) then from there the infected host mates with another one of its own species naturally and the next stage begins. Now a unique creature born of the mix of the first parasite's dna and the hosts emerges, capable of implanting its own embryo in any host with dna compatible enough to that of its host. (in this case, human.)
Lastly, this creature, would ultimately put its embryo into the space jockey. (its dna being compatible enough to humans, based on how that blue-ish guy looks, which is very, very humanoid) The idea of a 7 or 8 ft. alien creature, would be a bi-product of this last mixing. As the engineer/jockey looks to be around that height. So in this process some features of the first worm-like, possibly acid spitting creature, some of the squid-like creature(eyelessness, having tentacles which correspond to the "fingers" of a facehugger), and the rest being a mix of human and jockey race traits, and bingo, the xenomorph is born.
I think it's interesting but of course, if the planet that this film takes place on, is not LV-426 and I don't think it is mind you, you'd have to believe this accumulation of various creatures traits had to happen elsewhere before. So maybe it is after all, simply that one of the ampules contains the xenomorph dna, just as it holds that of other species. Oh well, it was worth noting and speculating on nonetheless. Hopefully, your time has not been wasted.
