An adult variant of Xenomorph XX121 spawned from the Dog-aliens on LV-178 were encountered by the crew of the DSMO Marion in 2159. Thanks to the DNA Reflex, this variant inherited certain physical traits from its host, specifically their greater size, strength, and dog-like physical stature.
These Xenomorphs were much larger than the typical human-spawned variation. They were quadrupedal in stature, though they were much more physically imposing and powerful than other quadrupedal variants such as the Runner. When the crew of the Marion first discovered them, the creatures were in a state of suspended animation that made them resemble inanimate, mummified statues. In fact, they were so completely sessile, that the humans initially assumed them to be nothing more than simple statues. Whether this state of hibernation was voluntary on the Xenomorphs' part or forced on them by the dog-aliens is unclear.
Some of these variants were aboard the derelict ship that crashed on LV-178, obviously born from some of its crew. After its crash, the creatures entered a state of hibernation, which to the miners of the DSMO Marion made them look like inanimate statues. They were subsequently awakened from their sleep by the miners, and in the ensuing struggle, one of them wounded Ellen Ripley.
The creatures were presumably destroyed along with the ship when charges set by the miners were detonated within it.