Unidentified SR388 lifeforms

Several unidentified lifeforms appear as SR388 fauna in Metroid: Samus Returns. While they presumably have filenames, these have not yet been discovered.

These creatures appear in the sidescrolling backgrounds of various areas on SR388, but are never directly encountered. This may suggest that they are not hostile creatures, unlike most of the others on the alien planet. They are original to Samus Returns and did not exist in Metroid II: Return of Samus, as the backgrounds in the latter are mostly black, with a few minor exceptions.

A brown, worm-like creature appears tunneling through the background of the southwest parts of Area 3, occasionally visible due to holes in the rock wall. It does not seem to have any sensory organs, aside from a mouth that is constantly open.

Other quadrupedal creatures with a rocky, plate-like torso, no separate head, crystals on their backs and greatly varying size appear walking around in the background of Area 4. The crystals on the back are also seen at other locations in the area, which suggests the species might be utilizing natural camouflage. Additionally, similar crystals with a black coloring are found at some locations in the same area, which could be dead or dormant specimens.

A mysterious unseen creature lurks in the background shadows of Area 4. Occasionally, its red eyes and flaring nostrils will become visible in the darkness before disappearing again.

Unnamed fish-like lifeforms appear in Area 5.

Samus is unable to physically interact with any of the above organisms which are exclusively located in the backgrounds and none of her weapons can harm them, including the Power Bomb. Despite their large bodies and sluggish speed, they seem to have somehow managed to avoid predation by Metroids.