Questions 1, 2 and 3 relate to material present on the tables; there are 5 sets of material (one per table). Question 4 relates to the rocks present on the black table in front of the blackboard; there is only one set of materials. Question 5 is theoretical (no material needed).

• #1-1. White specimen is a bivalve mollusc (genus Arca); dark specimen is a brachiopod (Order Rhynchonellida).
  • Mollusc (Arca): Valves are mirror images of each other, no plane of symmetry within each valves, thus must be a mollusc. Width > height; biconvex, strong costae on both valves. Long. straight hinge line.
  • Rhynchonellid: astrophic, height about equal to width, biconvex, no pdicle hole visible, strongly plicate shell, sulcus present.
• #1-2. Ligther colored, smooth specimen is pedicle valve of a recent Terebratula (brachiopod, Order Terebratulida). Brownish specimen of a fossil (Miocene)mollusc, again a species of Arca.
  • Terebratula: height and width similar, shell bilaterally symmetric, convex, astrophic, smooth cell with growth libes; large round pedicle hole present at top of shell; must be the pedicle valve.
  • Arca: costate shell, long straight hingeline, no plane of symmetry through shell.

• T1: concisely describe the trilobite, and indicate the position of its eyes on a simple drawing. From the relative size of the glabella, what do you think this trilobite's life style was? Do you think that this was an adult trilobite?
  • This is a Flexalymene meeki (p. 254, fig. J, K 1st edition; p. 261, fig. J, K 2nd edition); eyes are to the side of the strongly lobed glabella. The glabella is not very wide as compared to width of cephalon, thus it was probably a detritus eater (many fairly small meals). It is probably an adult (holaspid stage) since it has many segments (>10), well defined cephalon and pygidium.
• T2: concisely describe the trilobite. How did this trilobite live?
  • This trilobite is an Agnostus; cephalon and pygidium very similar in shape (p. 252 fig A 1st edition, p. 258 fig A 2nd edition), no eyes, small, 2 segments only. It probably lived planktonic, either close to surface or floating at depth.
• T3: this is only a part of a trilobite. Which part of the trilobite is it? What can you say about this trilobite's lifestyle from this fragment? What type of trilobite was this, from which character do you know this, and about when did it live?
  • The cephalon or head shield. The glabella is very wide relative to the cephalon, thus the trilobite ate few, large meals and was probably a predator or scavenger. The first seems probable, because the specimens has large schizochroal eyes and thus had excellent vision (p. 254 fig L 1st edition; p. 261, fig. L ). It must be a Phacopid (because of the schizochroal eyes; Phacops rana), and thus probably lived in the Devonian.
• T4: this is indeed a part of a trilobite. Which is the only part it could be, given the structure of a trilobite? What can you speculate about the lifestyle of this trilobite?
  • This is a glabella of the ilaenid trilobite Bumastus insignis (p. 253, fig. G 1st edition, p. 259, fig G. 2nd edition). It is a non-segmented part, so it can only be part of the head shield. Has been called 'snow plow' taxon, burrowing through mud. The large size of the galbella suggests a predator-type existence (large stomach); maybe catching burrowing, worm-like organisms.

  15 points

Determine to which order of Brachiopods each named brachiopod belongs, and which character(s) of the brachiopods you used to decide this.

• B1: Lingulepis paradoxides: Inarticulate; no hinge; shells of black material :phosphate; smooth. H/W slightly <1. Lingulida.
• B2: Atrypa reticularis. Inequal bi-convex (one side much more convex); short straight hinge line, pronounced sulcus, fairly fine ribbed shell. H/W close to 1. Spiriferida.
• B3: Leptaena richmondensis: concavo-convex, very flat, typical D-shaped outline, long straight hinge line; shell with fine ridges, some knobs (spine remains) H/W <1. Strophomenida.
• B4: Spirifer mucronatus. Biconvex, long straight hinge line, shell with coarse ribs, pronounced sulcus; H/W <<1. Spiriferida.
• B5: Juresania nebrascensis. Strongly concavo-convex, typical D-shaped outline, long straight hinge line; shell with very rough exterior, probably covered with spines during life; probably Productid group; H/W <1.
• B6: Terebratula sp.: Biconvex shell, H/W>1, typical 'lamp shell shape'; smooth surface, large pedicle foramen visible.

To which named brachiopod(s) is the 'mystery fossil' most closely related? To which order does it belong? How do you know?

• B7: mystery brachiopod: typical D-shaped outline, strongly concavo-convex; H/W <1. Probably Productid group of Strophomenida, thus most closely related to B5, then B3. D-shaped outline, straight hinge, concavo-convex shell.

Draw a tentative cladogram of B1-B7; include the table of characters used to draw the cladogram.

• Cladogram: the 'outgroup' is made up by the Inarticulate B1. Further up there are several possibilities, but you should have ended up with the 3 Strophomenid forms into a set of sister taxa, as well as the 2 Spirifers.

	HINGE	HINGE LINE	SULCUS	H/W	OUTLINE D	shell
B1	no	-	no	~1	no	smooth
B2	yes	straight	yes	~1	no	fine ribs
B3	yes	straight	no	<1	yes	fine ribs/ knobs
B4	yes	straight	yes	<<1	no	coarse ribs
B5	yes	straight	no	<1	yes	fine ribs,rough, knobs
B6	yes	curved	no	>1	no	smooth
B7	yes	straight	no	<1	yes	smooth, few knobs

10 points

• Rock nr. 1: Dominated by very many crinoid stems (Echinodermata), which by itself indicates a Paleozoic age. The shells present were Brachiopods (of various different species), and in some the small remains of the support for the lophophore could be seen. Note that in some brachiopods an internal septum was visible; these thus belong to the order Pentamerida.
• Rock nr. 2: Dominated by Bryozoa. A few crinoid stems (Echinodermata) present, as well as fairly common Brachiopods. The crinoid stems indicate it was Paleozoic.
• Rock nr. 3: Dominated by coiled and straight ammonites, with bivalves (difficult to decide whether bivalves of brachiopods), and one Nautilus, all representatives of the Phylum Mollusca. There were also a few rather porous, brown clups of material which are bone fragments (Phylum Chordates). The ammonites indicate a Mersozoic age.

a) What is the effect (if any) of fossil fuel burning on the carbon isotope composition of the shells of planktonic and benthic foraminifera? Does fossil fuel burning influence the difference in carbon isotope composition of planktonic and benthic foraminiferal tests?

• Fossil fuel burning adds isotopically light carbon to the ocean-atmosphere reservoir, and thus makes both benthic and planktonic shells isotopically lighter. It does not influence the difference between the two groups.

b) Human activities commonly result in eutrophication (highly increased productivity of diatoms and/or dinoflagellates). What (if any) is the effect of eutrophication on the carbon isotope composition of the tests of planktonic and benthic foraminifera? Does eutrophication influence the difference in carbon isotope composition of the shells of planktonic and benthic foraminifera?

• Eutrophication means that in the photic zone photosynthetic algae are very numerous, and they take isotopically light carbon out of the water to build their own organic matter. The shells of planktonic foraminifera (using the left over dissolved inorganic carbon) thus become isotopically heavier. The organic matter produced in the surface waters falls to the bottom where at least part of it is oxidized to inorganic dissolved carbon, which thus gets isotopically lighter. This dissolved inorganic carbon is used by the benthic foraminifera to precipitate their shell; the shells of benthic forams thus become isotopically lighter if surface productivity increases, and the difference between the planktonic and benthic isotopic signature increases.

c) Can you tell (without additional information being given) whether the carbon isotope composition of the tests of benthic foraminifera becomes lighter or heavier if there is both extensive fossil fuel burning and eutrophication? Why? Can you tell (without additional information) whether the carbon isotope composition of the shell of planktonic foraminifera becomes lighter or heavier if there is fossil fuel burning and eutrophication? Why?

• Both fossil fuel burning and eutrophication cause benthic foraminiferal shells to become isotopically lighter (see above), and we thus can predict that these get lighter.
• Fossil fuel burning adds isotopically light carbon to the whole ocean reservoir, but eutrophication causes high photosynthetic activity in the photic zone, taking isotopically light carbon out of the water. We can without further information not decide which of these effects is stronger, and we thus do not know whether planktonic foraminiferal tests become heavier or lighter.

d) What effect does melting of the Antarctic ice cap have on the oxygen isotope composition of planktonic and benthic foraminifera?

• Melting of polar ice caps adds isotopically very light oxygen to the whole ocean reservoir, and both planktonic and benthic foraminiferal shells thus become isotopically lighter.

e) In samples taken from a core the oxygen isotopic composition in shells of planktonic foraminifera decreases (becomes more negative) upward, while the oxygen isotope composition of the benthic foraminiferal shells remains unchanged, then how can you explain this pattern of change? (climate change, ice cap melting, or what?)

• This can not be the effect of melting of the ice caps, which would affect both groups. We can assume that one possibility would be that the surface waters get warmer, because these waters are much easier influenced by atmospheric temperatures than the huge mass of cold water in the deep oceans. Possibly, there was a strong increase in precipitation (rain is isotopically lighter than ocean water), influencing the surface waters. Neither of these efects can have been too extreme: if it was getting very warm we would expect some reaction from ice caps (if there were any to start with), or the high-latitude surface waters would warm and thus influence deep-water temperatures (and benthic foram tests). The precipitation effect could also not be very large, because if it was the salinity would get so low that planktonic foraminifera could no longer live.

f) If the surface waters at high latitude become warmer, then what will the effect be (if any) on the oxygen isotopic composition of the shells of deep-sea benthic foraminifera which live in the tropics?

• Deep ocean water is derived from high latitudes; if the high latitude surface waters warm then the deep ocean waters over the whole ocean including the tropics warm as well, causing the oxygen isotopic composition of benthic foraminiferal shells to get lower values.