THE INSECTIVORES 101 



conid. The molar teeth of both jaws show the specialized 

 feature of decrease in size from the first backwards. The gle- 

 noid fossa is broad antero-posteriorly and shallow in conform- 

 ity with the omnivorous type of dentition. 



In general then the teeth of Tupaia exhibit a tendency toward 

 the omnivorous adaptation less pronounced than that of Hy- 

 lomys. But Tupaia is an advanced type. Its ancestry can be 

 traced back to the Eocene of North America in which occurs 



Fig. 31. — Dentition of Bornean Tree Shrew (Tupaia tana, 9.331-1). An animal 

 of special significance because of the relationship of its ancestry with that of the 

 Primates. 



a Tupaiid, Entomolestes, the primitive characters of which in- 

 dicate that it lies close to the point of divergence between 

 modern Tree Shrews and non-Malagasy Lemurs. From this 

 we must infer that although in skull, skeleton and dentition, 

 Tupaia resembles the Lemurs quite closely it has attained the 

 Lemur-like features independently by parallel evolution. In 

 the study of teeth and skull there is often noted a tendency 

 in different orders or families towards evolution along paral- 

 lel lines, a tendency of very great importance which cannot 

 be too often emphasized. 



