This phylum contains peculiar animals that superficially resemble both the hydroid cnidaria, and the bryozoa, but are now not thought to be closely related to either. Only 150 species are described and these are for the most part microscopic, none exceeding 5mm in length.
Most Entoprocts are coastal marine species, commonly found in rock pools.
However, a single freshwater genus is also known. Entoprocts are sessile, filter-feeding animals that often occur commensally on other invertebrate or algal species. They may exist as isolated individuals, or as colonies. The Entoproct body comprises a muscular attachment disc equipped with foot glands , from which a stem or stems arise vertically. The dominant body component is a cup-shaped calyx, located at the apex of the stalk and containing all of the animals digestive and reproductive structures.