56 CUSP NOMENCLATURE CHAP. 



even earlier representatives of these families. Fig. 36 (p. 51) 

 illustrating a series of mammalian teeth will illustrate the above 

 remarks. That there is such a convergence in tooth structure 

 shows that it is, theoretically at least, possible to determine the 

 ancestral form of the mammalian tooth. Practically, however, 

 the difficulties which beset such theorising are great ; that there 

 are such divergent and such strongly-held antithetical views is 



sufficient proof of this. Two 

 main views hold the field : 

 one, which has found most 

 favour in America, and is due 

 chiefly to the labours and per- 

 suasiveness of Professors Cope, 



FIG. 38. Molar teeth of A, Plienacodus, and Scott, Osboril, and Others, IS 

 B, the Creodont Palaeonictis. Knd, endo- , 



conid ; hid, hypoconulid ; hyd, hypo- K11OW11 as " trituberculy. 

 conid ; med, metacomd ; prd, proto- The a l ternat i ve v j ew as urget l 

 oomd. (After Osborn and Wortman.) 



by Forsyth Major, "Woodward, 



and Goodrich, attempts to show that the dentition of the 

 original mammal included grinding teeth which were multi- 

 cuspidate or "multi tubercular." There is much to be said for 

 both views, and something to be said against both. 



This question is, however, wrapped up in a wider one. Its 

 solution depends upon the ancestry of mammals. If the Mam- 

 malia are to be derived from reptiles with simple conical teeth, 

 then the first stage in the development of trituberculy is proved. 

 On the other hand, however, the evidence is gradually growing 

 that the Theromorpha represent more nearly than any non- 

 mammalian group with which we are acquainted the probable 

 ancestral form of the mammals. These animals offer some 

 support to both the leading views. Cynoynathus had triconodont 

 teeth which, as will be pointed out later, are a theoretically 

 intermediate stage in the evolution of tritubercular teeth ; on 

 the other hand, the teeth of Diademodon and some others are 

 multituberculate, and have been very properly compared to the 

 multitubercular teeth of such primitive mammalia as the Ornitho- 

 rhynchus. Professor Osborn is no doubt correct in italicising a 

 remark of an anonymous writer in Science to the effect that in 

 Diademodon the teeth, though multitubercular, show the pre- 

 valence of three cusps arranged in the tritubercular fashion. 



1 See for a summary, Osborn, American Nat. Dec. 1897, p. 993. 



