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The subterranean Xenomorph was a variation of Warrior that digs underground. It appears in the comic Alien vs Predator: Duel in Issue 1. These may just be normal warriors adapting to their enviroment, but it unclear at the moment.
These aliens have Dorsal tubes that are bent inwards, much like a Juggernaut. They have sharp tips on their elbows and bulges on their heads unlike warriors, which have dents. They are also shown to have humanoid fingers and opposable thumbs. They also have a tail that looks more mechanical, due to the appearance of a predator's Whip.