Bryozoa

Early Ordovician to Recent

The encrusting bryozoan, Membranipora membranacea; Gymnolaemata > Cheilostomida > Membraniporidae. The encrusting habit is characteristic of many bryozoa, although some have erect colonies that resemble miniature corals. Bryozoa are commonly encountered even in intertidal rockpools, or found cemented on other organisms such as kelp or seashells. Image from: USGS, via Wikipedia, public domain

Bryozoans, or "moss animals," are aquatic, mostly marine, colonial organisms, superficially rather like coral. A few to many millions of these individuals may form one colony. The colonies range from millimeters to meters in size, but the individuals that make up the colonies are tiny; usually less than a millimeter long. Usually they encrust rocky surfaces, shells, or algae. The colonies may be soft-bodied or calcareous like corals. It is the latter that are most often fossilized. There are about 5000 living species, with several times that number of fossil forms known.

After approximately 250 years of scientific study, the sum total of accumulated human wisdom on the subject of bryozoan phylogeny is Nil.  Zero. Nada. It would be fair to state that we know as much about the phylogeny of entirely hypothetical Martian cryptobionts. Those, at least, have been the subject of intense speculation by learnèd folks who can get away with such speculations in the semi-popular press. Bryozoologists just throw their hands up -- like so many zoöids waving their happy lophophores about. Maybe they'll catch onto something that way -- but we are not optimistic.

For taxonomic purposes, the Bryozoa are classified as follows:

PHYLUM BRYOZOA
     Class Stenolaemata
          Order Cyclostomata
          Order Hederellida
          Order Trepostomatida
          Order Cystoporida
          Order Cryptostomida
          Order Fenestrida
     Class Gymnolaemata
          Order Ctenostomata
          Order Cheilostomata
     Class Phylactolaemata

MAK990511  ATW050910.

The following phylogeny is proposed by Palaeos contributer Christopher Taylor on the basis of Prothero, 1998. and should not be considered more authoritative than other phylogenies (assuming their are any). We have only included here because what would Palaeos be without its dendrograms? MAK121001

Scanning electron micrograph of part of a bryozoan colony showing male and female brooding zooids and feeding autozooids.. © 2008-2010 Australian Institute of Marine Science, Creative Commons Attribution license

Class Stenolaemata

These are marine bryozoans with tubular zooids with strongly calcified walls. The lophophore is protruded by action of annular muscles. Most forms lack an operculum. This was the predominant Bryozoan group during the Paleozoic. Some grew as lacy or fan-like colonies that became important reef builders and in some regions form an abundant component of limestones. Their numbers were greatly reduced by the terminal Permian extinction event.

Order Cyclostomata (= Tubuliporata)

Bryozoa with encrusting or erect colonies, many with communication pores. The skeletal structure is typically laminated. The aperture for each zooid (little animal) is either circular or polygonal. Late Ordovician to Recent. - about 250 genera

Order(?) Hederellida

A group of bryozoans similar to cyclostomatids; of uncertain relationships. Late Ordovician to Carboniferous.

Order Trepostomatida

Colonies generally robust; dendroid, encrusting, or massive. Ordovician to Triassic - 200 genera

Tabulipora acadica - (Family: Stenopridae) - Early Carboniferous of Nova Scotia

Order Cystoporida

Colonies encrusting or erect, robust or delicate. Crescent-shaped thickened strip or projections  (lunarium) around each aperture. Early Ordovician to Late Permian - 100 genera

Order Cryptostomida

Colonies erect, typically delicate; foliate, dendroid.(tree-like), or bilaminar sheets. Skeletons without communication pores
Early Ordovician to Late Permian - 90 genera

Order Fenestrida (=Fenestrata)

Includes some of the most amazing bryozoa. The colonies are erect, typically delicate; reticulate (net-like) or pinnate (fern-like). This order was previously included under the Cryptostomata.
Early Ordovician to Late Permian - 100 genera

Representative types

close up	entire colony
Family FENESTELLIDAE Archimedes wortheni Hall Early Carboniferous (Warsaw Formation - Early Visean, Arundian epoch) west Laurussia

Class Gymnolaemata

Mostly marine bryozoans with cylindrical or flattened zooids. Lophophore is protruded by action of muscles pulling on frontal wall. Includes the majority of living bryozoan species..

Order Ctenostomata

Uncalcified forms, including several that bore into calcareous substrates. Skeleton membranous or gelatinous. Opercula rare. Eggs brooded in body cavity. Almost all fossils are traces of boring forms Ordovician to Recent  - 50 named genera

Representative types	Systematic Classification
Suborder STOLONIFERINA Superfamily TEREBRIPOROIDEA family VINELLIDAE Vinella repens Ulrich, 1890 (above) Blackriveran (Sandbian) North America width of shell illustrated on top right: 3 cm more on Vinella (from the Union College Geology Department site) Suborder VESICULARINA Superfamily VESICULARIOIDEA family VESICULARIIDAE Bowerbankia recent - widespread	SUBORDER ALCYONIDIINA SUPERFAMILY ALCYONIDIOIDEA SUBORDER FLUSTRELLIDRINA SUPERFAMILY HAYWARDOZOONOIDEA SUPERFAMILY FLUSTRELLIDROIDEA SUBORDER VICTORELLINA SUPERFAMILY VICTORELLOIDEA SUBORDER PALUDICELLINA SUPERFAMILY PALUDICELLOIDEA SUBORDER VESICULARINA SUPERFAMILY VESICULARIOIDEA SUBORDER STOLONIFERINA SUPERFAMILY TRITICELLOIDEA SUPERFAMILY AEVERRILLIOIDEA SUPERFAMILY VALKERIOIDEA SUPERFAMILY ARACHNIDIOIDEA SUPERFAMILY TEREBRIPOROIDEA SUPERFAMILY HISLOPIOIDEA SUPERFAMILY PENETRANTIINA

Order Cheilostomata

These are calcified forms, usually with an opercula. Short-box-like zooeica chambers for the little animal). The eggs are usually brooded in ovicells (swollen spherical chambers in which the fertilized egg develops into a larva). The suborders are distinguished according to frontal calcification and mechanism of lophophore protrusion. This order includes the majority of recent Bryozoa
Late Jurassic - Recent.  1000 genera

Class Phylactolaemata

Non-calcareous freshwater bryozoans with no zooid polymorphism. Horse-shoe shaped lophophore.. No fossil record except for a few statoblasts (resistant wintering structures) from Quaternary sediments.

Credits

illustrations from the former The "Lesser" Protostome and Lophophorate Phyla page at University of Sydney Biological Sciences, from Brusca and Brusca, Invertebrates.1990.

References

Prothero, D. R. 1998. Bringing Fossils to Life: An introduction to paleobiology. WCB McGraw-Hill: Boston.

Links

The Bryozoa Home age - Recent and Fossil Bryozoa

University of California Museum of Paleontology -- Introduction to the Bryozoa - "Moss animals"