A HISTORY OF VERTEBRATES: BIRDS AND MAMMALS 501 



whereas rabbits have a reduced second pair hidden behind the large pair 

 of upper incisors. It is now believed that rabbits and the pika belong 

 to a separate order, the Lagomorpha, and that their resemblance to 

 rodents is a result of parallel evolution. 



Questions 



1. Contrast homoiothermic and poikilothermic vertebrates. 



2. How do wings support and propel a bird? 



3. Describe a typical feather. In what ways is it adapted for flight? 



4. Compare the structure of the wings of a pterosaur, bird and bat. 



5. In what ways are the internal organs of birds adapted for flight? 



6. How does Archaeopteryx differ from modern birds? 



7. List some modifications of birds' bills and feet. How are these correlated with meth- 

 ods of feeding and locomotion? 



8. What are the advantages to birds of nesting territories? 



9. What factors may have been involved in the evolution of the migratory habit? 



10. Distinguish between matnmals and reptiles. 



11. What are the major anatomic features of mammals that are correlated with their 

 increased activity? 



12. What is the importance of a placenta? What structures form it? 



13. List three ways in which monotremes are more primitive than other mammals. 



14. Why are marsupials particularly abundant in Australia? Give an example of a North 

 American marsupial. 



15. What is the most primitive group of eutherian mammals? 



16. W'hat features of man are a direct or indirect result of the arboreal adaptations of 

 man's primate ancestors? 



17. Distinguish between plantigrade, digitigrade and unguligrade foot postures. Give an 

 example of a mammal with each type. 



18. How have the molar teeth of ungulates been adapted for the animals' herbivorous 

 diet? 



19. How do perissodactyls differ from artiodactyls? 



Supplementary Reading 



Your attention is again called to the general references on vertebrates cited at the 

 end of Chapter 22. Those interested in the adaptation and habits of birds are referred 

 to Allen, Birds and Their Attributes, Thomson, Biology of Birds, and to a series of 

 fascinating articles written by Deevey, Griffin, Lack, Storer and Welty on various aspects 

 of avian biology and reprinted in Flanagan's Twentieth-century Bestiary. Further in- 

 formation on bird flight and superb illustrations can be found in Storer, The Flight of 

 Birds. The possible methods by which birds find their way in homing and on long dis- 

 tance migrations are explored and carefully analyzed by Matthews in Bird Navigation. 

 Those interested in learning to recognize the various kinds of birds should try using 

 Peterson's admirable Field Guides to Birds. 



The habits and natural history of mammals are considered in Hamilton, American 

 Mammals; and Bourliere, The Natural History of Mammals: those of the opossum, to- 

 gether with the fascinating folklore of this unusual creature, in Hartman, 'Possums. 

 Howell's Aquatic Mammals deals with the interesting adaptations of whales and other 

 mammals that have reverted to an aquatic mode of life. The primitive horses and camels, 

 the giant mastodons and mammoths, and other fascinating mammals that roamed our 

 continent in ages past are described in Scott, A History of the Land Mammals of the 

 Western Hemisphere. Burt and Grossenheider, A Field Guide to the Mammals, and 

 Hamilton, Mammals of Eastern United States, are useful guides for identifying the vari- 

 ous kinds of mammals. 



