| Geology 105 - Paleontology | ||||||
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At the end of this lab, you should be able to:
I. Crinoids
Hard part morphology: (#1128, 328, 1250, 1079, 1128, 24). Find a calyx, arms, columnals, holdfast. Note the bumps on the top of the calyx for articulation of the arms. Look carefully at the two unnumbered slabs and the specimen in the shadow box to see how all the parts go together.
Compare the variation in the columnals (#1149, 1710, 369, 1084, 1458), some displaying clear five-fold symmetry, others not.
II. Blastoids
Compare to crinoids. Primary diffferences: crinoids had coelomate arms (with body cavity inside) that they could extrude tube feet through, blastoids had simple arms and extruded tube feet through the calyx instead. Crinoids ate through complex arrangement of food grooves, blastoids through a simple mouth. Crinoid calyx has five-fold symmetry which is subtle; the calyx is made of complex arrangements of six-sided plates. Blastoids have simple and obvious five-fold symmetry.
#1222: Pentremites - These specimens are smashed. Find the mouth, spiracles and ambulacral area (where the tube feet extruded).
Other box - these blastoids are in better condition.
III. Echinoids
Resin block: Compare the whole animal with its internal skeleton. Find the mouth, anus, Aristotle's Lantern (jaws) and knobs on skeleton where spines articulate.
Hard part morphology:
There are two types of echinoids: "regular" and "irregular"
Regular urchins: These are the sea urchins you see in tide pools. Look carefully at the two preserved specimens, one with large "pencil" spines, the other with much smaller spines. Every spine is connected to the water vascular system, moved by "tube feet". The spines keep larval organisms from settling on the echnioid, as well as serving as protection from predation.
Flip the preserved specimens over (CAREFULLY) to look at the mouth parts - the "Lantern of Aristotle". 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.
Now look carefully at the specimens without soft parts or spines (e.g., #1087). The tiny holes are where the tube feet come through the skeleton. Also note all the many small plates that make up the skeleton. As the organism grows, it enlarges the pales, and adds new ones.
Irregular urchins (#1406, 129, 544, 1456) have tiny bristles that they use for burrowing through sand. They are infaunal deposit feeders. While all are solitary, some of the flattened forms (sand dollars) are gregarious. Find the pores for tube feet. Note bilateral symmetry. Locate mouth and anus - why are they not symmetrically located? On unnumbered specimen, note "petals" (ambulacrum) - grooves with pores for tube feet.
IV. Cystoids
#123, 533 - 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
Asteroids (#120) (Ord. to Recent) - "starfish"
Ophiuroids (no number, SFB 001) (Ord. to Recent) - "brittle stars"
These groups have a poor fossil record. As you can see from our specimens, they tend to disintegrate after death.
Edrioasteroid (Cambrian to Penn.) - encrusting suspension feeders
Helicoplacoids (Cambrian) - spiraling plates, mysterious biology
1. #381 - Identify the class of this echinoderm. Sketch the animal in life position, including any missing parts.
2. #1297 - Identify this organism. How is it preserved?
3. #242 - Identify. How did it eat?
4. #1411, 1233 - 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?