Lab #3: Brachiopods and Bryozoans

At the end of this lab, you should be able to:

1. Identify a fossil as an articulate brachiopod, inarticulate brachiopod, or bryozoan.
2. Be able to determine the order of an articulate brachiopod using the chart below.
3. Know the skeletal structure and material of each of these animals.
4. Know the ecological characteristics of each of these animals.
5. Know the geologic range of each of these groups.
6. Know a few important genera (mentioned by name in this handout) for each group.

Display

Brachiopods:

I. Soft part morphology - use fig. 12.1 to identify the lophophore and the muscles which open the shell.

II. Hard part morphology - Be able to find the valves, hinge line, beak, fold and sulcus (see handout)

Look at the range of morphologies in the different groups of brachiopods. You do not need to memorize these groups. You should understand the morphology well enough to be able to classify a specimen using the descriptions below. See the handout to understand the shape of the valves.

IIA. Linguliformea

These brachiopods (formerly called inarticulate brachiopods) are small, and almost all have shells made of calcium phosphate.  Many living linguliform brachiopods are infauna, though a few fossil forms were encrusters, living on rocks or other shelled organisms.  Some groups had tongue-shaped shells, while others are generally circular or ovals.  The phosphate shells are largely preserved as the thin original shell, darkened by heat, and carbonization of the organic material.

• #231 & 45 Lingula, #24, 646 & 902 Acrothele
  

II B-J Rhynchonelliformea

The great majority of brachiopods are in this group, formerly called articulate brachiopods.  These brachiopods have more robust shells made of calcite.  All are epifaunal.  Some attached themselves to rocky substrates, or to fragments of shell or pebbles in soft substrate.  Others lived unattached in soft substrates (mud or sand), anchoring themselves in place with spines, lying flat on the bottom, or leaning against each other in large masses.  See figure 12-9 in your book for info on life positions.

II-B: Modern brachiopod.  Look at the very delicate lophophore support inside the shell.

Look carefully at each group with attention to the features mentioned for each.  Use your handout to find these features.

• II-C. Orthids: long, straight hinge line with triangular notches on both valves, fine ribs, shallow fold and sulcus, biconvex.
• #1346 Plectorthis, #1348 Platystrophia, #774, 775 & 1378 Reserella, #85 Hebertella

• II-D. Strophomenids: concavo-convex shell with long hinge (D-shape).
• #942, 953 & 1494 Rafinesquina, #1373 Stropheodonta

• II-E. Productids: deep convex cup-shaped pedicle valve with spines, lid-like brachial valve.
• #638 Reticulatea, #22, Productus (the spines on our samples are broken off, but you can see the nubs)
  

• II-F. Pentamerids: biconvex with curved hinges. Internal walls create internal molds with deep clefts.
• # 44 & #116 Pentamerus.  These are both internal molds.  Look for the clefts (filled with calcite in one specimen) that show where the support wall was in the shell.

• II-G. Spiriferids: biconvex, strong ribs, long hinge line with wing-like shape. Deep fold and sulcus.
• #1424 & unnumbered Mucrospirifer, #1364 Spirifer

• II-H Atrypids: almost plano-convex, short hinge, circular shape.
• #556 Athyris, #1428 & 1497 Spinatrypa
  

• II-I Rhynchonellids: biconvex, short, bent hinge, pointed beak (V-shaped), deep ribs, deep fold and sulcus.
• #380, 567 Rhynchonella, #946, 1193 Lepidocydas, #947 Rhynchotrema
• 
  
• II-J Terebratulids: biconvex, large opening for pedicle, large overhanging beak, short, curved hinge, smooth shells, no fold or sulcus
• #564 Dielasma, #1618, unnumbered
  

Bryozoans

I. Soft part morphology:

• I-A: Resin block: The blue-stained material is the soft tissue of the tiny individual zooids.
• I-B: Modern bryozoan: This washed up on Dillon Beach.  Use the microscope to see the tiny pores where the zooids lived.  This is not a stony bryozoan; the skeleton is made of protein.
  

II. Hard part morphology

Be able to find the pores, and notice the variety in the shapes of the colonies. Shape, as in modern corals, is strongly tied to the environment - massive shapes in high energy water, delicate shapes in quiet water.  Bryozoans may look superficially like coral.  The zooids are typically much smaller than coral polyps, so the pores are much smaller on bryozoa than the calyx on coral.  On a coral, you usually can see the septa inside the calyx (on most scleractinans and colonial rugose).  Bryozoa do not have septa.

• II-A Branching forms:
• #1478 & 1479 Hallopora, unnumbered
• #104 Tabulipora
  

• II-B Massive forms
  
• #899 Aspidopora, #214 Monotrypa

• II-C Blade-shaped colonies
  
• #1487 Constellaria, #1102 Monticulpora

• II-D Fenestrate bryozoans - had large fans of lacy structures on a solid support structure
  
• #1642, 1835-1839 Archimedes (this is the support structure for this lacy fenestrellid - see picture)
  
• #53, unnumbered fenestrates
  

Questions

1. Resin block - Look carefully at the lightly stained tissues in this modern example of Lingula. Find the spiral support and the feathery tentacles of the lophophore.

2. #646 - From the preservation of this brachiopod, is it linguliform or rhynchonelliform? What group does it belong to?

3. #1389 - What is the function of the large hole in the beak? How could you be sure this is not a clam?

4. #1258 - From what we know about the life habit of living linguliform brachiopods, deduce whether this is an accumulation of dead brachiopods, or a catastrophic burial of living brachs.

5. #962 - How is this fossil preserved? What group does this species belong to?

6. #1520 - Look closely at the shell structure of this strophomenid. Is this impunctate, punctate, or pseudopunctate (use the diagram)? Can you tell by looking at the outside of the shell (be sure you look at the shell itself, not the encrusting sponges)?

7. #1257 - Is this a complete shell? How could you tell?

8. #354 - What group of brachiopods does this specimen belong to?

9. #569 - VERY GENTLY try to open this modern brach. Why doesn't it open?

10. #1216 - These are productid brachiopods.

• Use the handout to describe the shape of the valves.
• What are the small bumps on the larger valve?
• How were these brachs oriented in life (use fig 12.9 in the book to help you)

11. #1523 - These brachiopods were mislabeled in our collection as rhynchonellids, but they are actually the orthid Platystrophia. What characteristics tell you they are really orthids? What characteristics do they have in common with rhynchonellids? This is an excellent example of convergent evolution.

12. #953 - This specimen of Raphinesquina has evidence of two types of organisms attached to the shell.

• What kind of organism encrusts the pedicle valve (the convex valve)?
• How did this brachiopod orient itself when it was alive - domed side up or domed side down? (use the diagram of brachiopod shapes, and think baout what the best orientaton for a filter feeder would be)
  
• Did these organisms attach themselves to this brachiopod before or after it died?

13. Place these brachiopods in their proper groups.

 
14. Examine one of the slabs of Ordovician rock from Cincinnati. Are these accumulations of dead organisms, or a catastrophic burial of living organisms.? How many kinds of brachiopods can you identify (to genus level - almost every brach in the slab is displayed somewhere in the lab today).

15. #642, 1095 Prasopora was a massive colony of bryozoa shaped something like a gumdrop. Find the cross-section through the colony to see the poorly preserved autopores of the zooicia.

16. #53 - Find the autopores in this fenestrellid bryozoan. In life, how would the lacy structure of this bryozoan be oriented? Explain the perforations in the colony - what is the advantage of being shaped this way?

17. #1335 - Contrast the delicate structure of this bryozoan with Prasopora. What differences would you expect to find in the environments in which each lived?

18. Unlabeled slides. Look at the cross-section through this bryozoan. Using the picture, find the mature region, immature region, autopores and mesopores (use handout).