262 INTRODUCTION TO EVOLUTION 



confronting zoogeographers but belongs properly in a later portion of this 

 discussion (pp. 265-267). 



Before the coming of man, with his intentional and unintentional intro- 

 duction of foreign species, Australia apparently had only bats, rats, and 

 mice as representatives of placental mammals (pp. 191-192), the group 

 which predominates in other regions of the globe. A dog, the dingo, is also 

 present but may have been introduced by early man. 



The AustraUan realm is unique as the home of the only living represen- 

 tatives of the group of mammals which lay eggs, the monotremes (p. 189). 

 These representatives are the duckbilled platypus {Omithorhynchus) and 

 the spiny anteater {Echidna) (Fig. 12.2). 



Aside from this sparse representation of placental mammals and mono- 

 tremes, Australia is populated by an odd assemblage of marsupials (Fig. 



^wJ^"-?"^ **N . 



••■>. 





*r^-s 



-<:^ 

 -j^^^-- 



r r^ 





FIG. 12.2. Monotremes. Echidna (spiny anteater), left; and Omithorhynchus (duckbilled 

 platypus), right. 



12.3). In many ways they parallel the adaptations of placental mammals in 

 the rest of the world, affording striking examples of that parallel evolution 

 which we have stressed in other connections. Thus we find kangaroos of 

 assorted sizes and means of livelihood. Most of them are terrestrial, though 

 the tree kangaroo has forsaken life on the ground for life in trees. The great 

 red kangaroo is the closest Australian approach to the swift-moving, graz- 

 ing animals of other continents (deer, antelope, horses, and so on). 



The koala, a slow-moving, nocturnal marsupial which has captured the 

 popular imagination as a living "teddy bear," lives in eucalyptus trees, 

 feeding on the leaves. Marsupial moles burrow in the ground just as do 

 true moles in other parts of the world. Wombats are marsupials which have 

 developed rodentlike teeth and have habits much like those of our wood- 

 chucks. Some phalangers resemble squirrels, while the flying phalanger 



