Animals Before Man 



based partly on the arrangement of the bones 

 forming the support of the fore limb (the 

 shoulder girdle), which is in many respects 

 like that of those egg-laying mammals, the 

 platypus and echidna, and partly on the char- 

 acter of the teeth. In most reptiles the teeth 

 are simple in structure, with a single root, and 

 all the teeth are made on the same pattern, 

 although they may differ greatly from one 

 another in the matter of size. But these 

 strange reptiles have their teeth variously 

 modified, whence the group as a whole is called 

 Anomodontia (anomalous toothed) ; while the 

 name of Theromorpha (beast-formed) was also 

 given to it in allusion to the resemblances some 

 portions of the skeleton present to the corre- 

 sponding parts in the lowest living mammals. 

 One division of these anomodonts has been 

 named Theriodontia (beast-toothed), because 

 their teeth, like those of mammals, are divisible 

 into incisors, canines, and molars ; and another 

 has been styled Dicynodontia (two canine- 

 toothed), on account of having two long teeth, 

 one on either side of the upper jaw. These 



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