Nipper Nerius

Nipper nerii (plural of nerius) live in the openings of burraroms' burrows. This protects them from their numerous predators, such as bulky hammerheads. Whenever they feel threatened, they will loosen their spines' grip on the surrounding walls and slip into their mini-burrows. They feel threatened whenever something comes near them, and therefore are difficult for predators to observe. They might also be easily frightened by approaching organisms because their vision is poorer than their ancestor's. Good vision was unnecessary for Nipper nerii, since they stay practically immobile in a burrow in the shadow of the largely predator-less burrarom.

Nipper nerii no longer have fins on their sides, on account of the fins' uselessness in burrows. The spines on their backs have grown outward in an asymmetrical formation. Nipper nerii use their spines to lodge themselves in burrows.

Nipper nerii are only able to burrow into the openings and mounds of burraroms' burrows because the stabilizing mucous in the burraroms' burrows prevents them from burrowing further. Nipper nerii burrow in a swimming motion, akin to an Earth sandfish.

Notes: Nipper Nerii are named after their mouths' resemblance to Nipper Plants. They do not actually nip, and indeed cannot bite. I [Coolsteph] had difficulty finding a name for them.