ORGANIC ADAPTATION 



321 



life. We may select from the Placental Mammals a small Malayan 

 insectivorous animal known as Gymnura, which is allied to the 

 Hedgehogs, as most similar among living Mammals to the gen- 

 eralized or focal type of terrestrial Mammal. Gymnura has rela- 

 tively short pentadactyl limbs with the entire palms and soles rest- 

 ing flat upon the ground (plantigrade) and therefore essentially 

 adapted for comparatively slow progression. (Figs. 201, 202.) 



H. CARNIVORA 



III. ARTIODACTYLA 



IV. CARNIVORA 



XIL MARSUPIALIA 



XL CHIROPTERA 



VIII. EDENTATA IX. PRIMATES 



Fig. 202. — Diagram of parallelism in evolution and adaptive radiation in 

 Mammals. I, Gymnura; II, Bear; III, Camel; IV, Badger; V, Anteater; 

 VI, Seal; VII, Dolphin; VIII, Sloth; IX, Gibbon; X, "Flying" Squirrel; 

 XI, Bat; XII, Kangaroo; XIII, Jerboa. (From Hegner, after Newman and 

 others.) 



Radiating from this focus, adaptations for rapid running (cur- 

 sorial adaptations) are chiefly evident in a lengthening of the 

 limbs. Thus, for example, in the Dogs, Foxes, and Wolves, the 

 effective limb length is increased by raising the wrist and heel 

 from the ground and walking merely upon the digits (digitigrade) ; 

 while in Antelopes, Horses, and hoofed runners in general, the 



