CHAPTER VIII 



Nesodontidae 



This family is characterized by the teeth being hyp- 

 sodont, the second upper incisor and the third lower in- 

 cisor being enlarged into caniniform teeth, the upper molars 

 complicated by the development of cristae, limbs short, 

 feet tridactyl and semidigitigrade. 



B 



Fig. 79. -4, upper and a lower molars 2 of Proadinotherium; B, upper and b lower molars 2 of Coresodon; C 

 upper and c lower molars 2 of Neudon — 1/2 natural size. 



In the Santa Cruz, the family is represented by the two 

 genera Nesodon and Adinotherium. In the Deseado we 

 find Proadinotherium evidently ancestral to Adinotherium 

 and very little differentiated from it. Ameghino has de- 

 scribed a genus, Pronesodon, which is evidently ancestral 

 to Nesodon. I have referred Coresodon to this family be- 

 cause the molars of the upper and lower jaws are very 

 close to those of Adinotherium. Ameghino has also de- 

 scribed two genera, Nesohippus and Interhippus, based on 

 upper molars which are very similar in pattern to Adi- 

 notherium and which I believe belong to this family, if 

 they prove to be valid genera, of which I have some doubt, 

 feeling that they will prove to be the deciduous upper pre- 



