(Solved): EXERCISES 1. Articulate brachiopods have a well-developed mechanical hinge that allows them to open ...

EXERCISES 1. Articulate brachiopods have a well-developed mechanical hinge that allows them to open and close their two shells (valves) easily (see Appendix, p. A-7). These forms have few muscles. Examine the modern-day brachiopod Terebratella, and compare it with the specimens of Lingula that you studied in the previous lab. Terebratella is an articulate brachiopod; one pair of muscles (the adductor muscles) closes the valves, and another pair of muscles (the diductors) opens them. Because of the interlocking nature of the teeth and sockets of the hinge, other, more complex, movements between valves are not possible. A. On specimens of Terebratella with the soft tissue still present, you will see that one valve has the pedicle attached and the other valve has a large and conspicuous filter-feeding device called the lophophore. The first valve is called the pedicle valve and the second, brachial valve. Are the two valves the same size and shape? (YES) (NO) B. If not, which one is larger? (PEDICLE VALVE) (BRACHIAL VALVE) C. Which valve has the greatest curvature along the outside from the hinge (or beak) to front edge? (PEDICLEVALVE) (BRACHIALVALVE) Open and close the "cleaned" valves of Terebratella, noting how the hinge elements fit together. On the inside of the brachial valve are two strut-like supports for the lophophore, and, on both valves, you can see muscle scars (shallow depressions in the shell). D. What happens when you add a very small amount of dilute hydrochloric acid to the shell? E. Which of the following is the probable chemical composition of this shell? (CALCIUM PHOSPHATE) (CALCIUM CARBONATE) F. What is the fossilization potential for articulate brachiopods?