EVOLUTION OF THE SKULL AND TEETH OF EOCENE TITAN0THERE3 



253 



V 



w 



m 



I 



Recit^ra^daiionS 

 NetM cliarcioiers, similar, hu-i 



ept 



Dnylu.) 



jillomeiroyvs 

 New proporiions disii-noiiz>e 



oj ea-ch phylum. Dijjeveni 

 -ow alt oiher phyla. 



t,n evey xj phyL 



FiGUBE 210. — Skulls showing different numerical and proportional characters in five separate phyla of 



titanotheres 



Similar numerical characters (rectigradations, A, B) and dissimilar proportional characters (allometrons, C, D), all arising independently in 

 descendants of the same ancestors. Each of the five phyla (I-V) exhibits similar rectigradations of the premolar teeth and in the osseous 

 horn rudiments (H) but dissimilar allometrons of the sliull ( C) and of the foot bones {D). pa'', mes^, New cuspules on the teeth! H, rudi- 

 diments of the newly arising horns. I, Eotitanops, a dolichocephalic ancestral form; II, Palaeosyops, brachycephalic; III, Telmatherium, 

 mesaticephalic; IV, Manteoceras, mesaticephalic; V, Dolichorhmus, dolichocephalic. 



