Rallinids

Rallinids are a small, cosmopolitan group of marine invertebrates belonging to the phylum Mollusca. They are characterized by their shell, which is typically flattened and coiled in a planispiral manner, meaning the shell coils in a single plane. The aperture of the shell is often semicircular and lacks a columella. Rallinids are predominantly found in shallow, soft-bottom marine environments, burrowing into sand or mud. They are detritivores, feeding on organic matter found in the sediment.

This group is relatively poorly understood, with many species described based on shell morphology alone. Their soft bodies are rarely observed, making detailed ecological and behavioral studies challenging. The taxonomic placement of rallinids has been debated, but they are generally considered to be gastropods, though their precise relationship to other gastropod clades is not fully resolved. Fossil evidence suggests that rallinids have existed for a considerable geological period. Their small size and cryptic lifestyle contribute to their infrequent encounters by researchers, leading to ongoing discoveries and revisions of their classification and distribution.