Bryozoa ("moss animals") Ordovician to recent. Exclusively colonial. Zooicium is colonial structure, zooid is individual cavity. Has digestive system, mouth with tentacles, separate excretory opening. 17,500 fossil species in all. What are the nearly microscope holes in this fossil? What is the trophic mode of the organism in the picture above? filter-feeder mud processor algae grazer active predator What habitat or environment is suggested by the presence of this organism?.