So basically theres gonna be a new type of aliens introduced that can eggmorph. Thats cool, although in the first movie we've seen Kanes Son being able to do it, so thats too bad they didnt let you guys go that way. As of today, the only source marrying the two procreation methods is the Alien 3 novelization, and as of today the only source hinting at the explanation of the existence of both ridged and smooth head aliens is the Aliens movie itself (the chestburster was born with smooth head, therefore hinting at ridges coming with age)