Reconstructing Ancient Animals
Creating an Ordovician Diorama

You have now had a chance to look at the fossils which we find in middle Tennessee.  This exercise addresses the question:

This exercise was inspired by the article "What color was your dinosaur?"  published in Learning from the Fossil Record, a remarkable collection of exercises for teaching geology.
 
 

Brachiopods:
How do we know what Paleozoic brachiopods were like when they were alive.  We know that they were marine animals, becauses we find them in limestone, but what else can we find out about them?

Where can we get more information about brachiopods?

Let's look at the fossils themselves

Ordovician brachiopods take two basic forms.  Most of them are bi-convex, that is, shaped like little nuts.  Others were concavo-convex, with one shell fitting inside the other liked stacked spoons.
Bi-convex brachiopods
Examples:  Hebertella, Platystrophia, Rhynchotrema
These brachiopods have a small hole at the hinge in their shell.  This indicates that part of the animal may have extended out of that hole, perhaps a way to attach to the bottom.		 Concavo-convex brachiopods
Examples:  Strophomena, Rafinesquina, Leptaena
These brachiopods don't have holes in their hinges, so they probably didn't attach to the bottom.
When we find fossil brachiopods, we usually find them in groups.  It is common to find a dozen brachiopods in a single slab of rock.  This is true of all kinds of brachiopods.
Let's look at modern relatives
You've probably never seen a living brachiopod, but they do exist.
Follow this link see a picture of modern brachiopods
Although brachiopods look a lot like bivalve mollusks on the outside, they are very different on the inside. They fed by filtering tiny bits of food out of the water with a muscle covered with tiny tentacles called a lophophore.
 
Let's Make Brachiopods

Materials:  Pasta shells (both medium and large), clay, white pipe cleaners, white glue.

Bi-convex brachiopod:  Take two pasta shells and break them until they fit together to make a round form.  Fill the inside space with clay. This represents the brachiopod animal.  Cut a strip of pipe cleaner, and press it into the clay around the top. (This represents the lophophore or feeding mechanism).  Take the pieces apart, put glue on the shells and the pipe cleaner and put them back together again.  Take a small piece of pipe cleaner.  Stick one end of it in the bottom of the brachiopod and the other in a piece of clay, which will serve as a base for the brachiopod.  Brachiopods, in reality donít make bases.  Their pedicles are either attached to some hard surface, a shell or rock, or are sunk into the mud. (As this is a new species, I name it Pasta krogerensis)

Concavo-convex brachiopod:   Take two pasta shells and break them until one fits spooned into the other.  Fill the space between the two shells with clay as before.  You will notice that there is much less room for brachiopod in this type than in the first one.  Cut and fit a pipe cleaner lophophore, and glue the shells, the clay and the pipe cleaner together as above.  Strophomenids donít have pedicles.  Set your brachiopod concave side down on the floor of your diorama. (You get to name this one.)

 

Bryozoans:
Bryozoans are colonial animals.

Lets look at the fossils
The bryozoan colonies we find come in four general shapes:  tree-shaped; frond-shaped; encrusting; and free-standing
 
Tree-Shaped Bryozoans
Examples:  Constellaria, Hallopora, Homotrypa
These bryozoans formed comples twig like structures like this Constellaria.
Colonies sometimes start by encrusting over a shell and then sending up branches. 		 Frond-Shaped Bryozoans
Examples:  Heterotrypa, Constellaria, 
Encrusting Bryozoans
Examples:  Atactoporella
Some bryozoans grow as thin colonies over other animals.  Atactoporella grew over a small stail.		 Free-Standing Bryozoans
Example:  Prasopora
Some bryozoans formed thick multi-layered colonies over the shells of other animals.  Prasopora grew on the shells of a small mollusk called Ctenodonta and a samll brachiopod called Resserella.
Like brachiopods, bryozoans tend to be found in clusters.
Let's look at their modern relatives:
Like brachiopods, bryozoans are still with us.  There are lots of pictures of current bryozoans at the Bryozoan Website.  Check out what they look like and what color they are. Bryozoans are closely related to brachiopods (They are both members of the superphylum Lophophorata).  Like brachiopods they are filter feeders, who eat microorganism using tiny tentacles.  Here's what the individual animals look like.

There are modern bryozoans which, like Attactoporella, encrust snails.  They do not kill the snails they grow on, but have a symbiotic relationship with them.

Let's Make Bryozoans

Materials:  pipe cleaners, clay, snail shells,  mussel shells, paint

Tree-like bryozoans:  Pick pipe cleaners in the color you want your bryozoans.  We now know that bryozoans can be a wide variety of bright colors, although we can't be sure what color any particular species of fossil bryozoan was.  Because each bryozoan colony consists of clones, we should make each colony a single color.  Take a piece of clay and make a base.  (you can use the clay plain, or have it encrust on a mussel shell.)  Then cut up the pipe cleaners and make it into a tree form.  Finally, you should paint the clay base to match the pipe cleaners.

Frond-like bryozoans:  I haven't yet figured out how to make models of these yet.

Encrusting bryozoans:  To make Atactoporella, pick a color paint, and paint a snail shell.  You can have it on a dead snail, by painting an empty snail shell, or you can have the colony in a symbiotic relationship put a snail in the shell (see Mollusks below)

Free-standing bryozoans: To make Prasopora, take a small mussel shell and make a covering over it out of clay.  The covering should be a good deal larger than the snail shell.  When the clay dries, paint it a color of your choosing.

 
 

Crinoids:Ý
"Indian Money" is one of the commonest fossils in the area.  However, because it is such a very small fragment of the original animal, it is rather hard to figure out from the fossil what the animal lookled like

Let's look at the fossils:

We often find individual crinoid stem segments, which look like beads.Ý We also find a group of them strung together.Ý What do you think the complete animal looke like?

Although complete animals are not common, they are sometimes found.Ý Here are some pictures of fairly complete fossils.
 

Lets look at modern relatives:
 
Here is a site which lets you identify the modern relative.

Crinoids are echinoderms.Ý Think of them as starfish on stalks.Ý Like bryozoans, crinoids did make their own bases.Ý What color were crinoids?Ý Like bryozoans, modern crinoids are very colorful.Ý To see pictures of them, look at Charles Messing's Comatulid Crinoid Page..  For more information on crinoids, see the Bioquest Crinoid Education Project.
Ý

Let's Make Crinoids

Materials:Ý clay, pipe cleaners, white beads, small colorful feathers

This exercise is taken from the exercises developed at Falls of the Ohio State ParkÝ
Cut a piece of pipe cleaner 4-5 inches long.Ý Make a base out of clay so that it looks like tree roots and is thick enough to hold the crinoid up.Ý Put beads on the pipe cleaner except for the top 1/2 inch.Ý Put a small ball of clay on the top .Ý Put five feathers (all the same color) into the ball of clay.Ý Trim the feathers to an appropriate size.
Mollusks - Gastropods

Let's look at the fossils

What is most remarkable about fossil snails is that they look so much like modern ones.


What did ancient snails eat?  Modern snails vary a great deal in their habits.  Some are vegetarians like the algae eaters in your fish tank or the land snails which eat your garden.  Others are scavengers.  The rest are predators, which drill holes into the shells of other animals and eat them.  We assume that there were all three types in the Ordovician Period. We know that there were predatory snails, because we find the telltale snail-holes in fossil shells. Put one of your snails on the shell of one of the other animals.
 

Let's Make Gastropods

Materials:  modern snail shells, clay, white glue, tooth picks

Make a snail-sized teardrop shaped piece of clay and glue it to the shell.  To make the snail's horns, break off the ends of a tooth pick and stick them on the snail.  Put at least one of your snails on a brachiopod to show predation.

Mollusks - Cephalopods

Let's look at the fossils

There are several common cephalopods found in middle Tennessee.  One of them, Actinoceras, has a straight, segmented shell shaped like a cone.  As with crinoids, we mostly find small fragments of the total animal.

While most of the fossil cephalopods we find are small, occasionally we find some that are huge.  I have found an imprint of an Actinoceras, whch I estimate was at least 10 feet long.


Let's look at modern cephalopods.

The most common modern cephalopods, squids and octopi, do not have shells.  However, there is one extant cephalopod, the chambered nautilus, which does.  We assume that Actinoceras looked a lot like the chambered nautilus with a straight shell.

As a class, cephalopods have good eyesite, are very mobile, and are by far the most intellegent of the mollusks.
 

Let's Make Cephalopods
Materials:  "Shells" copied from the form in your materials onto card stock, tape, white glue, googly dolls' eyes (available at craft stores), white or tan pipe cleaners

Copy the shell form onto card stock and cut it out.  Roll it and tape it.  Glue a clay head into it.  Glue eyes onto the head.  All modern cephalopods have good vision.  Put quite a large number of pipe cleaner tentacles into the front of the head.

 
 

Most of the information for this diorama comes from Invertebrate Fossils by Boardman, Cheatham and Rowell.