Lab 7: Invertebrate Paleontology This week’s activity is based on Exercise 9 in

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Lab 7: Invertebrate Paleontology
This week’s activity is based on Exercise 9 in your lab manual, Invertebrate Paleontology. However, because we can’t all look at fossils together, most of what you do will be an alternative activity involving online images and interactive 3D digital models of fossils. Your lab manual will still be a valuable reference to you.
To begin this lab, read the introduction to Exercise 9 in your lab manual and watch the recorded presentation. Instead of completing the questions in the lab manual, answer the questions below, then submit your answers in a document.
Part I. Use the graphs in figures 9-1 and 9-2 to answer these questions.
How did the diversity of marine organisms (shown by the number of families in figure 9-1) change from the beginning of the Cambrian period to the end of the Ordovician period? (Cambrian is shown as C with a line through it and Ordovician as O on the graph.)
What happened to the number of marine families at the end of the Permian period (shown as P on figure 9-1)? What is going on at this point in Earth’s history that caused this change in diversity?
How does the diversity of the Paleozoic Fauna compare to the diversity of the Modern Fauna during the Silurian period (shown as S on the graphs)? How does the diversity of these two faunas compare to the diversity today, shown on the far-right side of the graphs?
Part II. The following website has 3D models we will use to look at fossils up close. Look at the bottom half of the page to see links to each major phylum of living things. You can click on the 3D models to rotate them.
https://www.digitalatlasofancientlife.org/vc/
Links to an external site.
Beginning with the Cambrian fauna, examine the trilobites (Trilobita) listed under the Phylum Arthropoda.
4. The Cambrian explosion brought the world the earliest known animal predators. No wonder arthropods like these trilobites developed hard shells! Observe the 3D models of the trilobite species Eldredgeops crassituberculata. How do you think the posture of the animal’s body might have helped it to survive? You can compare it to other trilobite fossils on the page to see a more normal trilobite resting posture.
You can find more detailed information about the Paleozoic and Modern faunas in the Digital Encyclopedia linked below.
https://www.digitalatlasofancientlife.org/learn/
Links to an external site.
Corals: The Paleozoic had coral reefs, much like today. However, these were made by different kinds of corals than we have now.
5. Navigate to Phylum Cnidaria and find the corals called Rugosa. Observe the digital model of Zaphrentites spinulosum, which is sometimes called a “horn coral.” Is this a solitary coral or a colonial coral? Does it have septa (singular septum)? 6. For comparison, look at the corals called Tabulata and find the model of Favosites favosus. Zoom in on the hexagon-shaped (6-sided) corallites where the colonial coral animals lived. Do these corallites have septa?
Brachiopods are among the most common Paleozoic fossils. They look like clams but come from another phylum and are quite different on the inside. 7. Move to the Phylum Brachiopoda. Examine the first digital model of the modern brachiopod. Which is larger, the brachial valve or the pedicle valve
Examine the fossil of Mediospirifer audaculus. When facing the sulcus, numbered 2, is the specimen mostly symmetrical (the same on both sides of the sulcus) or asymmetrical (different on opposite sides of the sulcus)?
What is the function of the brachiopod’s lophophore?
Bryozoans are colonial relatives of the brachiopods, but they are easy to mistake for corals.
Find the Phylum Bryozoa. Examine the fossil of Prasopora sp., looking closely at the holes on the surface where the bryozoan animals lived. Are these bigger or smaller compared to the corallites of the tabulate coral? (This is a good way to tell bryozoans and corals apart!)
Crinoids belong to the Phylum Echinodermata, to which starfish and sea urchins also belong.
Find the Phylum Echinodermata, Class Crinoidea. Examine the 3D models of the crinoid stem segments. What are these single pieces of the crinoid stem called? Why are they such common fossils?
Like many Paleozoic Fauna animals, crinoids have had to evolve to deal with more advanced predators in the modern age. Some have gained the ability to move to avoid being eaten. What are the two ways that modern crinoids can move?
Echinoids are also echinoderms, but unlike crinoids, they are part of the Modern fauna.
Find the Phylum Echinodermata, Class Echinoidea. Echinoids have defenses against predators that crinoids lack. How do echinoids protect themselves from predators? How does this differ between regular echinoids and irregular echinoids?
Bivalves belong to the Phylum Mollusca, which are the most common invertebrate fossils from Mesozoic and Cenozoic oceans. They are also common on the menus of seafood restaurants!
Observe the 3D model of the quahog clam Mercenaria mercenaria. Do the two valves (shells) look basically the same or different? How is this type of symmetry different from the symmetry you saw for the brachiopod in question 7?
Gastropods are extremely common in the modern ocean. They belong to the Phylum Mollusca.
Observe the model of the fossil snail Naticarius plicatella (about halfway down the page). Does this snail show dextral or sinistral coiling? Which type of coiling is more common in gastropods?
Cephalopods, like squids and octopuses, are some of the most important index fossils. Many fossils species bear unique suture patterns that can be used to tell them apart. Navigate to the following page to view ammonoid cephalopods:
https://www.digitalatlasofancientlife.org/learn/mollusca/cephalopoda/ammonoidea/
Links to an external site.
Find the species Sphenodiscus lenticularis. Based on Figure 9-13 in your lab manual, which type of suture do you see in this shell?
Although the website doesn’t tell us the age of this Sphenodiscus fossil, we can make an educated guess based on the suture pattern. Based on your answer to question 15 and the information on the website, during which geologic period or periods is it most likely that this animal lived?

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