Cussion Questions

1. What paleontological evidence would convince you that Tyranno-saurus and Triceratops actually fought one another? Would the evidence more likely come from body fossils or trace fossils, and why?

2. What paleontological evidence would convince you that Pachyce-phalosaurus actually butted heads (or at least flanks) with one another? Would the evidence more likely be from body fossils or trace fossils, and why?

3. Given the following speculative masses and speeds for each genus of pachycephalosaur, calculate the kinetic energy generated by each.

a. Homocephale: 145 kg, 2.5 m/s b. Stegoceras: 25 kg, 4 m/s c. Stygimoloch: 75 kg, 3.7 m/s

4. Examine the genera lists in Table 13.1 and 13.2, then omit all of the genera that only come from Mongolia to judge the impact of expeditions to Mongolia on what is known about marginocephalians.

a. What percentage of the original genera is left after making such omissions?

b. Which taxa are affected the most by your omission: pachycepha-losaurs, non-neoceratopsians, or the neoceratopsians?

c. Taking this a step farther, speculate how evolutionary scenarios of marginocephalian evolution would be changed by the omission of Mongolian-only species.

5. The evolutionary sequence summarized for Late Cretaceous centro-saurines in the western part of North America seemed very persuasive, but what are some alternative hypotheses to explain the observed changes through time of the centrosaurine taxa? What new evidence would either falsify or modify the previous hypothesis?

6. Review the factors given in the chapter explaining why pachycepha-losaurs and ceratopsians are so differently represented in the geologic record despite their geographic proximity and overlapping geologic ranges. What are some other explanations, and what new (or previously found) evidence would support each explanation?

7. Test the speculation that centrosaurines locked horns with one another more often than chasmosaurines by classifying the genera mentioned as having skull defects into each clade. Is any trend noticeable? What evidence, either from body fossils, trace fossils, or both, would convince you further of your conditional acceptance or rejection of your hypothesis?

8. The chapter refers to healed wounds in the parietal frills and rib fractures of ceratopsids as trace fossils. Why are these features trace fossils rather than body fossils?

9. What supplementary evidence associated with Protoceratops would help to determine which of the two body types (small-frilled and

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