god this particular topic makes my head explode. i absolutely hate the idea of the alien games and comics, its total rubbish, they're almost as cheesy as power rangers and all the different types of transformers out there (transformers generation 1 is the bomb - a little off the subject but hey)
there is only these strains of alien -
egg
hugger
burster
drone
warrior
queen
the dog alien and predalien are just the result from being within hosts other than humans.
also drones do not morph into queens as shown with praetorians, queens are born as queens - this can be proved by watchin alien 3 which clearly shows the queens crown when she is a chestburster.
if you wanna think these 'other' species exist then fine, but for me, praetorians, scorpion aliens, and all the other ridiculous species are nothing but marketing for the younger audiences.