Introduction

This week we will start the study of the Lophophorata by examining the Bryozoan Phylum (aka the Phylum Ectoprocta) a group of organisms that feed with a ciliated hollow, crown shaped structure called the lophophore, similar to the feeding structure used by the Brachiopods (studied in next week's lab) and the Phoronids.  Bryozoans are colonial, mostly (but not entirely) marine lophophorates.  They appeared in Ordovician time and rapidly diversified, with major extinctions in Permian and Triassic time.

    A bryozoan colony or zoarium can be as much as 2 feet across, yet the individual animals, the zooids, are quite tiny-only about 1 mm in length.  The tiny tubular holes through which the lophophores extend (the zoecia) are much smaller than the corallites visible in colonial corals-they are really just pinhole sized features.  The SEM photograph shown at the top of this page gives you an idea of what the openings are like.
 
    Bryozoans prefer hard surfaces, and are often found encrusting upon other shell material.  Organisms that live on the surface of other organisms are called epibionts, and bryozoans are commonly found as epibionts.  You will find many examples of epibionts in your fossils that you will collect at  Caesar's Creek, and you will find tiny patches of bryozoans on the surfaces of the brachiopods and horn corals.
 
 

Phylum Bryozoa, (Ordovician-Recent) 

Basic Facts & Terms to Know about Bryozoans:  They are:
1.	Eukaryotes
2.	Metazoans with organs, true tissues, nervous, muscular, and reproductive systems
3.	characterized by a  Lophophore feeding structure for benthic filter feeding, a U shaped gut with anus outside the lophophore ring.
4.	Bilateral in symmetry
5.	free-swimming in larval stage (larvae):  sessile (encrusting as adults
6.	able to reproduce  sexually and asexually (through budding)
7.	structurally supported by calcium carbonate exoskeleton called the zooarium
8.	Fossil forms are marine, but freshwater forms do exist.  Sessile and typically encrusting
9.	Second or third most common fossil of the Paleozoic (following brachiopods)

Part I.  Examine the commonly found fossil bryozoans and draw 4, labelling the zooarium, the zoecium, the  Order,, and the growth habit (massive, branching, encrusting, or fenestrate). (20 pts)

Part II. Today, we will do a group exercise on cladistics and cladograms (20 pts.). 

Notes on Bryozoans
Bryozoan Classification is complex, and recent cladistics analysis (Anstey, 1990) indicates that many of the traditional Orders are probably paraphyletic (that is, each group may have derived from a single ancestral taxon, but the group does not include all the common descendents of the the most recent common ancestor).

Here are the generally recognized Orders for the commonly found fossil bryozoans:
Class Stenolaemata (Ordovician-Recent)
Order Trepostomata (Ordovician-Triassic)
Order Cryptostomata (Ordovician-Permian)
Order Fenestrella (Early Ordovician-Permian)  This one contains the index fossil Archimedes, a bryozoan guide fossil for the Mississippian
Order Cyclostomata (Early Ord-Recent)

Class Gymnolaemata (Ordovician-Recent)
Order Cheilostomata (Jurassic-Recent)

Archimedes, a Fenestrate bryozoan from the Mississippian-commonly preserved without the delicate branching zoarium.
Shown with permission from the University of California at Berkeley Museum of Paleontology