CHAPTER XIX 

 THE DECIDUOUS DENTITION 



Specialized Character of the monophyodont dentition in Mam- 

 mals — The deciduous teeth do not represent in miniature 

 the permanent teeth — Milk Dentition of Modern Man — ■ 

 The Predmost mandible — Milk dentition of Anthropoids — 

 Deciduous dentition of Old-World and American Monkeys 

 — Mingled ancestral and adaptive features of the decidu- 

 ous dentition — The milk dentition in orders other than 

 Primates — The Marsupial dentition— Foramina of the 

 tooth crypts. 



There is no doubt that Mammals were originally derived 

 from Reptiles possessing a polyphyodont dentition, one in which 

 there occurred many successional series of teeth. Replacement 

 of teeth is known to have occurred in Cynodonts and in Juras- 

 sic Mammalia. It is therefore natural that the less specialized 

 of modern Mammals at least should exhibit two series, the 

 temporary, deciduous, lacteal or milk set and the replacing, 

 successional, or permanent set. When we find Mammals which 

 possess only one functional series of teeth such for example as 

 the Seals,* Sloths, toothed Whales and many Rodents, we must 

 regard the feature as evidence of great specialization. This 

 interpretation is borne out by the fact that it is usually in those 

 members of any order more advanced in other respects which 

 exhibit the so-called monophyodont character. Consequently 

 Ave consider that Mammals Avhich have retained a complete 

 milk dentition consisting of incisors, canines and milk molars, 



*The milk dentition of the Seals is shed before birth. 



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