[2] Acrothoracicans bore into calcareous material such as mollusc shells, coral, crinoids or hardgrounds, producing a slit-like hole in the surface known by the trace fossil name Rogerella.

They have from four to six pairs of feathery limbs, or "cirri", which they project out of their borings to catch drifting detritus for food.

[4] The cyprid larva in Lithoglyptidae and Trypetesidae have a well-developed carapace which can completely enclose the body, a developed thorax with thoracic limbs and a distinct abdomen and telson.

In Cryptophialidae the cyprid larvae are reduced; the carapace is much smaller, and the thorax and the thoracic limbs are rudimentary.

A dwarf male is sometimes found attached to the mantle or wall of a female's burrow.