They inhabit sand and mud beneath shallow coastal waters and can survive in relatively anoxic environments.

In many Bursovaginoidea, one of the major group of gnathostomulids, the neck region is slightly narrower than the rest of the body, giving them a distinct head.

It has a pair of cuticular jaws, supplied by strong muscles, and often bearing minute teeth.

The basal plate is used to scrape smaller organisms off of the grains of sand that make up their anoxic seabed mud habitat.

The mouth opens into a blind-ending tube in which digestion takes place; there is no true anus.

After fertilization, the single egg ruptures through the body wall and adheres to nearby sand particles; the parent is able to rapidly heal the resulting wound.