Ordovician to Recent. Virtually all marine, Bryozoans are exclusively
colonial. They share superficial similarities to corals but can be
distinguished from corals in that the individual zooids (critters) are
nearly microscopic (pinhole size or less) in size. They are most
closely related to worms and brachiopods. The most common colony
shapes are incrustations (coatings) and branched forms.
Along with corals they were important components of Paleozoic reefs.
One distinctive genus, Archimedes, (large picture) is the remains
of the central stem of a spiral fan colony.
