Geology 105 - Paleontology
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Lab #7 : Echinoderms

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

1. Identify a fossil as a crinoid, blastoid, regular echinoid or irregular echinoid.
2. Know the skeletal structure and material of each of these animals.
3. Know the ecological characteristics of each of these animals.
4. Know the geologic range of each of these groups.
5. Know a few important genera (mentioned by name in this handout) for each group.

Display

I. Crinoids: There are modern crinoids, but they usually lack the stems that are so typical of their Paleozoic and Mesozoic relatives.  The calcite plates that make up the organism were held together with soft tissue, and usually fell apart upon the death of the organism.  If you find a complete crinoid, it typically means that the organism was rapidly buried.

A. Hard part morphology: You can find everything but the holdfast on the two beautifully preserved and prepared crinoid plates, or on the replicas (#1128 Cactocrinus, #328 Encrinus)

• 1. Arms (#24) - Crinoids are filter feeders.  they have arms with very fine little branches, all made of tiny plates of calcite.  In life, the water vascular system of the animal reached intot he arms, and tiny tube feet projected from the arms to catch food particles.  In some modern crinoids, the food is passed to a canal that runs down the arm, and the food is moved along the canal to the mouth at the base of the arms.  In other modern crinoids, the entire arm is inserted into the mouth and the food particles scraped off.
  
• 2. Calyx (#43, 1050 Eucalyptocrinus, #537 Dolatocrinus, #196 Genneaocrinus) - the "cup" that held the body, made of interlocking calcite plates. Notice the bumps on top of the calyx for articulation of the arms.
  
• 3. Columnals (#1458, 1149, 369, 1514, 1464, 65) - the "stem" of the "sea lily".  Pay attention to the variation.  Som columnals are round, others have star-shaped holes in the center, and some are even completely star-shaped, reflecting the 5-fold symmetry of the echinoderms.  Notice the cleavage faces that cut through the calcite plates in specimen #1710.  Note that there is no way to know whether these columnals come from blastoids or crinoids except that blastoids are typically smaller with very fine columnals.
  
• 4. Holdfast (#1250) - the crinoid anchored itself with arms that spread into the sediment.  Modern crinoids can roll up their holdfasts and move to new locations.

B. Build a crinoid:  Use a calyx (#1513 Eucalypto), a section of columnals (#1164), and the holdfast (#1250) to build a crinoid.  Our crinoid is a bit of a Frankenstein crinoid, since we're mixing species, but you get the idea.  Do you think your crinoid would have been this tall or taller in life?

II. Blastoids

• The blastoid calyx is made of calcite plates fused together.
• The animal has star-shaped feeding structure called the ambulacram that looks like the petals of a flower.  The tiny arms attached to the ambulacrum.  These tiny arms collected small food particles which were passed down the arms to the ambulacrum, then up the groove in the center of the ambulacrum to the mouth at the top of the calyx.
• At the top of the calyx you can see five small round openings with another star-shaped opening in the center.  The star-shaped hole is the mouth.  The largest of the five round holes is the anus.  The rest of the round holes are called spiracles, and they were probably used for respiration as the animal pulled in sea water and extracted the oxygen from it.
  

B. Compare to crinoids (#1053 crinoid, #1512 blastoid): picture

• Crinoid calyx has five-fold symmetry which is subtle; the calyx is made of complex arrangements of six-sided plates. The blastoid calyx has simple and obvious five-fold symmetry.
• Crinoid calyx is a broad open cup with articulating surfaces at the edges where the arms attached.  The plates were held together with soft tissue, and usually fell apart after death, making intact crinoid calyxes rare. The blastoid calyx was fused together, so it is always found as a unit, though it may be crushed.
  
• Crinoids had five arms, robust at the bottom and progressively branching as they went up.  Blastoids had many tiny arms attached to the star-shaped feeding structure (ambulacrum) that looks like a little flower.

C. Various blastoids to look at:

• #1222, #1425 Pentremites: these specimens are smashed.  See if you can find the ambulacrum (the flower petals), the spriacles or the anus.  The mouth is smashed flat in all these specimens.
  
• unnumbered: These little guys are better preserved

III. Echinoids

A. Anatomy & hard part morphology:

• 1. Resin block:
  
• On the left is the whole animal.  Notice the mouthparts (called the lantern of Aristotle) in the middle, the spines on the outside.  
• On the right is the skeleton.  Look for the little knobs where the spines articulate.
• In the middle is the mouthparts (lantern) by itself. 
  

• 2. Regular echinoid: These are the sea urchins you see in tide pools.  The urchin uses these plates to scrape up food, whether it is grazing algae or stripping away the soft parts of coral as a predator. Regular urchins are benthic epifaunal creatures, generally preferring rocky substrates.  They also use the lantern to scrape holes in the rock where they rest between high tides.
  
• unnumbered: large pencil urchin, smaller urchin with fine spines.  FRAGILE - handle very carefully.
• On the little urchin you can see the tip of the lantern, and you can see how the spines attach.
• On the pencil urchin, look first at the top surface.  This echinoid has two different kinds of spines on the top surface - the big pencils meant to keep settling larvae off the animal, and to prevent predators from getting a good bite - and the tiny tan spines that protect the rest of the body.  Flip it over GENTLY and you can see even tinier spines near the mouth, and dried-up tube feet (the orange-brown things that look like tiny mushrooms.   Notice that the tube feet are organized in lines.
• The spines are attached to by muscles. You can see the remains of these fibrous muscles on the pencil spines that have fallen off.
• #1087, #1233: skeleton
  
• On these specimens, the mouth is in the center on the bottom, and the anus is in the center on the top. Neither of these specimens has the lantern preserved. 
  
• Notice the radiating pattern of stripes with tiny holes.  These holes are where the tube feet come through the skeleton.  The animal moves using the tube feet on the bottom, and the tube feet on the top help control the spines.
• Notice the bumps where the spines articulate.
• #4, 13, 59: spines
• Echinoid spines are solid masses of calcite.  WHile the rest of the skeleton often falls apart after death, and especially for regular urchins, is destroyed in the high energy environments they live in, spines of all sizes are well preserved and common in the fossil record.
  

• 3. Irregular echinoids: These urchins have tiny spines that look like bristles that they use for burrowing through sand. They are infaunal deposit feeders, though some live on or just barely beneath the surface of the sediment..
  
• unnumbered white urchins: Look for the flower-shaped ambulacrum where the tube feet stick through the skeleton. Note the bilateral symmetry (unlike the radial symmetry of the regular urchins). Locate mouth and anus - why are they not located directly opposite each other as in the regular urchins?
• unnumbered big white urchin, #1406: Find the pores for the tube feet, the mouth and the anus.
• unnumbered sand dollars: Some irregular urchins are fairly flat.  Sand dollars are gregarious and live in large herds.  They can be fantastically ecologically disruptive as the burrow their way through the sediment in huge numbers

IV. Cystoids

• #123, 533 Caryocrinites - These are the "head" and plates of a cystoid, a Paleozoic echinoderm. They have no close living relatives but crinoids, but are rather different than crinoids. Cystoids had flexible stalks, no holdfast, and either many small arms or a few very large arms.

V. Other Echinoderms: Some of these groups have a poor fossil record. As you can see from our specimens, they tend to disintegrate after death.

• Asteroids (#120) (Ord. to Recent) - "starfish"
• Ophiuroids (no number, SFB 001) (Ord. to Recent) - "brittle stars"
• Edrioasteroid (Cambrian to Penn.) - encrusting suspension feeders
• Helicoplacoids (Cambrian) - spiraling plates, mysterious biology

Questions

1. unnumbered - Identify the class of this echinoderm. Sketch the animal in life position, including any missing parts.

2. unnumbered - Identify this organism. How is it preserved?

3. #242 - Identify. How did it eat?

4. unnumbered, #1297 - Find the mouth and anus on these two urchins. Why are they positioned differently? What adaptive advantage is there to each organism?

5. What are the light-colored blobs in the slab? How do you know they are echinoderms?

6. #248 - What part of the crinoid is this?

7. unnumbered - Why are there more pores on the bottom than on the top of this echinoid? What is its probable life habit?

8. In this slab, there is one blastoid found as most are, with no arms. Look very carefuly at the other, which has its arms intact. Blastoid arms are very rarely preserved. Why?

9. #1077 - identify the kind of echinoderm.

10. #1299 - identify the kind of echinoderm.