The shadow barnacle existed as a silica parasite that inhabited the world of Coruscant.
This tiny crustacean attached itself to structures utilizing root-like feeders to draw sustenance. When danger approached, it would withdraw into its protective shell. Reproduction in the shadow barnacle occurred via the dispersal of "egg seeds" along with "sperm pollens" that were released into the surrounding air.
Its anatomy included a tube-shaped mouth, a protective shell, and anchor tendrils that could be pulled back. Furthermore, it possessed claw-legs that allowed for movement, and external gill filaments that could be drawn back inside its mouth.
These creatures proved resilient enough to endure the vongforming process that affected Coruscant.