'I move', ῥύγχος rhúnkhos "snout") is a phylum of small marine invertebrates that are widespread in mud or sand at all depths as part of the meiobenthos.

[2] Kinorhynchs are limbless animals, with a body consisting of a head, neck, and a trunk of eleven segments.

The body wall consists of a thin syncitial layer, which secretes a tough cuticle; this is molted several times while growing to adulthood.

The mouth is located in a conical structure at the apex of the head, and opens into a pharynx and then an oesophagus, both of which are lined by cuticle.

Beyond the oesophagus lies a midgut that combines the functions of a stomach and intestine, and lacks a cuticle, enabling it to absorb nutrients.

Smaller ganglia are also located in the lateral and dorsal portions of each segment, but do not form distinct cords.

In most species, the sperm duct includes two or three spiny structures that presumably aid in copulation, although the details are unknown.