BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 

 Vol. 25, pp. 403-405 September 15, i914 



PROCEEDINGS OF THE PALEONTOLOGICAL SOCIETY 



EECENT EESULTS IN THE PHYLOGENY OF THE 

 TITANOTHEEES ^ 



BY HENRY FAIRFIELD OSBORN 



{Bead before the Paleontological Society December 31, 1918) 



Eecent discoveries have modified the authoi-^s earlier opinions as to 

 the lines of descent of the titanotheres and still further changes are an- 

 ticipated with increase of knowledge of the connections between Upper 

 Eocene, or Uinta., titanotheres and those of the Lower Oligocene, or White 

 Eiver. 



The main lines of division are indicated in the proportions of the 

 limbs, whether cursorial, mediportal, or graviportal; the proportions of 

 the skull, whether mesaticephalic, brachy cephalic, or dolichocephalic ; the 

 development of fronto-nasal horns, whether accelerated or retarded; the 

 molarization of the premolar teeth, whether accelerated or retarded; 

 the presence or absence of incisor teeth; the abbreviate or elongate, the 

 triangular or oval form of the fronto-nasal horns as developed in Oligo- 

 cene times. 



With these criteria the various phyla may readily be distinguished as 

 follows : 



A. Wind River titanotheres, face more elongate than cranium : 



I. LambdotheriinjTe, light-Hmbed, cursorial.. Genus, Lanihdotherium 

 II. Eotitanopinfp, medium-limbed, mediportal. Eotitanops 



B. Bridger and succeeding titanotheres, cranium longer than face: 



III. Palseosyopinte, short-limbed, brachyceph- Genus, Falaosyops, 



alic. Limnohyops 



IV. Telmatheriinre, mesaticephalic to dolicho- Telmatherium, 



cephalic. Sthenodectes 



V. Diplacodontinse, dolichocephalic, with ac- Diplaeodon 



celerated molarization of the premolars, 



imperfectly known. 



VI. ManteoceratiniB, mesaticephalic to brachy- Mmiteoceras, 



cephalic, accelerated development of the ProtitanothcHum 



horns, mediportal. 



1 Manuscript received by the Secretary of the Geological Society June 15, 1914. 



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