532 



CHORD ATA, 



Cursorial Adaptation, 



This is not so strongly marked as some of the others, as it merges 

 into the primitive terrestrial. As examples, we may take marsupial 

 dog, dog, pig, ox, sheep, rhinoceros, horse, and other Ungulata. 



1. Incidental group : tirsidce or bears, vitLstelidiT. or weasel family, 

 viverridcE or civets. They are not well marked off from the primitive 

 terrestrial, but can on 

 occasion move rapidly 

 on hard ground. They 

 show an incipient raising 

 of the body upon the 

 toes, a leading feature of 

 the cursorial type. 



2. Transition group : 

 ^og,felidLe{ox cat family), 

 pig, rhinoceros, tapir, 

 kangaroo. This shows 

 an increasing acquirement 

 of the ability to move fast 

 over hard ground either 

 to catch or to escape. 

 The digitigrade mode of 

 locomotion is acquired 

 and the claws in many 

 cases commence to form 

 hoofs. Here also com- 

 mences a reduction in 

 the number of the toes 

 to four or three. 



3. True cursorial : 

 horse, sheep, ox, deer, 

 &c. These types show 

 the ultimate cursorial 

 modification. The toes 

 are reduced to two, pair- 

 ed, or one unpaired, and 

 bear hoofs. The clavicles 

 tend to disappear. The 

 carpus and tarsus are 

 reduced and many of 

 the elements fuse. The 

 proximal elements be- 

 come dovetailed into the 

 distal (diplarthrous) as a 

 palliative against the tor- 

 sion due to rapid loco- 

 motion on hard ground. 

 All these three cursoria 

 types are herbivorous. 



