Bryozoa are tiny, colonial, dominantly marine animals with lophophores. The colonies are encrusting, stick-like, massive, or delicately branching fans. Individuals in the colony are about 1 mm in diameter, and occupy tubular or box-like chambers, open at one end. The aperatures leading to each living chamber are very small and usually require a hand lens or microscope to see clearly.

Bryozoa feed on microscopic organisms filtered from water by ciliated tentacles (lophophore) surrounding the mouth. The mouth leads to a U-shaped digestive tract ending in an anus near the mouth. Several kinds of specialized individuals may be included in the colony. Modern bryozoans occur in tidal flat to deep shelf environments in both clean and muddy water.

Fossil bryozoans first appeared in the Ordovician, and until the Silurian and Devonian, both massive and twig-like forms predominated. During the Mississippian, Pennsylvanian and Permian, fan and slender branch types were more common. Triassic bryozoans were rare, but new groups became extremely abundant in the Jurassic and extended to the Recent.

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Last updated on February 24, 1997-jlc.