Prasopora, extinct genus of bryozoans, small colonial animals that formed mosslike or encrusting growths, especially characteristic of the Ordovician Period (488.3 million to 443.7 million years ago). Prasopora generally is characterized by caplike colonies domed on top and flat on the bottom. The hard framework of the colony is composed of calcium carbonate, which formed the closely packed tubelike structures that housed the individual animals in the Prasopora colony.