A small encrusting bryozoan may be seen in the lower left hand corner of the shell. The Whitewater Formation of the Upper Ordovician Cincinnatian series is known to contain Ambonychia sp. Caritodens demissa , Cyrtodontula umbonata , and Anomalodonta gigantia . Homotrypa flabellaris , a unilaminate bryozoan. Bryozoans are colonial, filter-feeding organisms that are almost entirely marine.
Bryozoans bear a striking resemblance to coral, but they are more closely related to brachiopods.
Individuals, known as zooids, are able to collect oxygen and expel wastes by diffusion. Each zooid measures about 1 mm in length and is joined to others by common tissue. Maculae, or bumps, on the colony's surface are concentrations of a single type of zooid. The specialization of zooids allows a colony to use its energy efficiently. A bryozoan's colonial skeleton, or zooarium, is usually composed of calcite.