I don't think that's the Deacon or the classic Giger Xenomorph. Probably another proto-morph, like the Deacon, though.
Remember what Ridley Scott said:
"Well, really it's "Alien." They're going to go to the planet where the engineers came from, and come across the evolving creature that they had made. Why did they make it? Why would they make such a terrifying beast? It felt bio-mechanoid, it felt like a weapon. And so the movie will explain that, and reintroduce the alien back into it."