54 



MAMMALIAN DENTITION 



a depression at the base of the crown indicating incipient divi- 

 sion of the root into two. 



Although these fragmentary specimens undoubtedly repre- 

 sent stages in the evolution of the Mammal they are probably 

 too specialized to be actual mammalian ancestors. Having 

 noted their mammal-] ike characters we can but say as we said 

 of the Cynodonts that Mammals probably arose from some 



mg 



Fig. 13. — Mandibles of Microconodon tenu. ; rostris (upper figure) and Dromatherium 

 syJvestre (lower figure). (After Osborn.) The mandible of Microconodon is seen 

 from the lateral and that of Dromatherium from the mesial aspect. Abbreviations. — ■ 

 a., angle; c, canine: en,, condyle; cr., coronoid; i., incisors; mg., groove for Meckel's 

 cartifage; m., molars; p., premolars; lb, the fourth or fifth molar of Microconodon and 

 2b, the second molar of Dromatherium both much enlarged. 



creature like them: that Nature was trying her hand and these 

 represent one of her many experiments which, since it did not 

 ultimately succeed, was discarded after trial. 



THE MULTITUBERCULATA 



Another group of Mammals representing one of Nature 's trial 

 efforts is that known as the Multituberculates. These animals 

 like the Protodonts first appeared in the Triassic but lingered 

 on until the Basal Eocene when they finally became extinct. 

 From certain skeletal features we infer that they were mar- 

 supial in character but in no direct way allied to modern Mar- 



