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What anatomical constraints cause human jaws to be incapable of pleurokinesis? If humans were capable of pleurokinesis, how would their chewing be changed and what effect might this have on food choices?

Examine Tables 11.1 and 11.2 and count the number of genera that occur with each of the following time divisions: Early Jurassic, Middle Jurassic, Late Jurassic, Early Cretaceous, Late Cretaceous. What general trend in ornithopod diversity can you hypothesize on the basis of these data? What are possible sources of error in your analysis? (Hint: Making a bar graph with the number of genera on the /-axis and time divisions on the x-axis may help illustrate your point.)

3. A currently accepted hypothesis about Maiasaura is that they lived in communal nesting grounds where many individuals of the same species occupied an area at the same time and returned to it annually. What new evidence could change the current interpretation to one that would indicate that at least some Maiasaura mothers may have lived a solitary existence, raising their juveniles without others of their species nearby?

4. Hum a popular song for a minute, then abruptly open your mouth while trying to continue to hum the song.

a. How did the sound change, especially with regard to its frequency?

b. How did its wavelength change in accordance with the frequency?

c. Based on your preliminary experimentation, do you think that some hadrosaurids would have been more likely to have opened or shut their mouths when using low-frequency sounds?

d. Would the hadrosaurids have been inhaling or exhaling while making their sounds? On what basis can you make such an assumption?

During a warm day (35°C) of the Early Cretaceous in western North America, a herd of iguanodontians are browsing through a coastal forest when a pack of dromaeosaurs begins stalking them. The lead dromaeosaur, only 15 meters away from an iguanodontian at the back of the herd, steps on a twig from an angiosperm. The twig breaks with a loud crack that is heard by the iguanodontian, alerting it to the presence of the predators. Two seconds after hearing the sound, it makes a loud warning sound to the others in the herd.

a. Using the given data and information presented previously in this book, what are probable species representatives of the dromaeosaur and iguanodontian that lived in the same area and at the same time?

b. What evidence from the fossil record supports that the species of dromaeosaur was a pack hunter that preyed upon the species of iguanodontian?

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