246 



TITANOTHEKES OF ANCIENT WYOMING, DAKOTA, AND NEBRASKA 



the base, although the phyletic sequence through the middle 

 to the upper beds is not so clear. Symborodon suddenly appears 

 in the middle beds. 



The names of three of the genera thus recognized 

 were subsequently changed, for the reasons given, as 

 follows: For " Titanotherium Leidy" was substituted 

 Menodus Pomel; for " Ilegacerops Leidy" was substi- 

 tuted Brontops Marsh; for "Symborodon Cope" was 

 substituted Megacerops Leidy; " Brontotherium Marsh" 

 was permanently accepted. The phyla subsequently 

 were called subfamilies. (See below.) 



RECLASSIFICATION OF THE EOCENE AND OLIGOCENE 

 SUBFAMILIES BY OSBORN (1914) 



Original reference. — Geol. Soc. America Bull., vol. 25, 

 pp. 403-405, Sept. 15, 1914 (Osborn, 1914.409). 



Reasons for reclassification. — Osborn makes the 

 following statement : 



Recent discoveries have modified the author 's earlier opinions 

 as to the lines of descent of the titanotheres, and still further 

 changes are anticipated with increase of knowledge of the 

 connections between upper Eocene, or Uinta, titanotheres and 

 those of the lower Oligocene, or White River. 



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 frontonasal 

 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 tri- 

 angular or oval form of the frontonasal horns as developed in 

 Oligocene times. 



The new arrangement. — With these criteria the vari- 

 ous phyla were distinguished in 1914 as follows: 



A. Wind River titanotheres, face longer than cranium: 



I. Lambdotheriinae, light-limbed, cursorial: 

 Lambdotherium. 

 II. Eotitanopinae, medium-limbed, mediportal: 

 Eotitanops. 



B. Bridger and succeeding titanotheres, cranium longer than 

 face: 



III. Palaeosyopinae, short-limbed, brachycephalic : 



Palaeosyops, Limnohyops. 



IV. Telmatheriinae, mesaticephalic to dolichocephalic: 



Telmatherium, Sthenodecies. 

 V. Diplacodontinae, dolichocepahlic, with accelerated 

 molarization of the premolars, imperfectly known: 

 Diplacodon. 

 VI. Manteoceratinae, mesaticephalic to brachycephalic, 

 accelerated development of the horns, mediportal: 

 Manteoceras, Protitanotherium. 

 VII. Dolichorhinae, mesaticephalic to dolichocephalic, 

 limbs, so far as known, abbreviate: 



Dolichorhinus, Mesatirhinus, Sphenocoelus, Meta- 

 rhinus, Rhadinorhinus. 

 VIII. Menodontinae, mesaticephalic to dolichocephalic, 

 with abbreviate, triangular horns, with incisor teeth 

 reduced or wanting, feet and limbs elongate: 

 Menodus { = Titanotherium), Allops. 

 IX. Brontopinae, brachycephalic, horns abbreviated, 

 rounded, or oval, incisors persistent: 



Brontops {= Megaceratops^") , Diploclonus. 



" Error; should have been Megacerops. 



B. Bridger and succeeding titanotheres — Continued. 



X. Megaceropinae, mesaticephalic to extreme brachy- 

 cephalic, horns elongate, vertically placed, no in- 

 cisor teeth: 



Megacerops {^Symborodon). 

 XI. Brontotheriinae, mesaticephalic to brachycephalic, 

 horns elongate, transversely flattened and diver- 

 gent: 



Brontotherium. 



The free use of subfamily divisions to express the 

 distinct phyletic series is similar to that which the 

 author adopted in the phylogeny of the rhinoceroses. 

 More conservative usage would have divided the titano- 

 theres into four subfamilies only. Of these names 

 of phyla those assigned to Nos. II, IV, V, VI, VIII, 

 IX, X, and XI had apparently not hitherto been pub- 

 lished, and those assigned to Nos. I, III, and VII, 

 although they had been used in previous publications, 

 mostly by other authors, were now used in a more 

 restricted sense. 



Other subfamilies awaited further study and the 

 discovery of connecting forms, namely : 



Diplacodontinae = ancestors of Menodontinae or Bronto- 

 theriinae. 



Eotitanopinae = ancestors of Palaeosyopinae. 

 Rhadinorhininae = ancestors of Megaceropinae. 



Each subfamily name is carried back as far as possi- 

 ble — that is, to the point, even very remote, where the 

 subfamily characters and tendencies of evolution are 

 first clearly and unmistakably manifested. 



SPECIES WRONGLY REFERRED TO THE TITANOTHERES 

 Palaeosyops minor Marsh, 1871 (=Anchippodus minor) 



Original reference. — Am. Jour. Sci., 3d ser., vol. 2, 

 p. 36, 1871 (Marsh, 1871.1). 



Type. — "A molar tooth, from the right lower jaw, 

 and probably by some other less characteristic re- 

 mains" from Grizzly Buttes, Bridger Basin, Wyo. 



Present determination. — This specimen was wrongly 

 referred to Palaeosyops, as was recognized by Marsh, 

 Cope, and others. The specimen pertains to the order 

 Tillodontia. 



Helotherium procyoninum Cope, 1872 



Original reference.— Fed. Bull. No. 2, p. 466, 1872 

 (Cope, 1872.2). 



Synonymy. — LambdotTierium procyoninum Cope, 

 Tertiary Vertebrata, pp. 631, 711, pi. 24, fig. 22, 1884 

 [1885] (Cope, 1885.1). 



"Syn.? of OroUppus pumilis," Hay (1902.1, p. 612). 



Hyracotherium procyoninum Matthew, Am. Mus. 

 Nat. Hist. Bull., vol. 12, p. 45, 1899 (Matthew, 

 1899.1). 



OroMppus sp. Granger, Am. Mus. Nat. Hist. Bull., 

 vol. 24, p. 227, 1908 (Granger, 1908.1). 



Daeodon shoshonensis Cope, 1878 



Original reference. — Pal. Bull. No. 30, "December 3, 

 1878" (Cope, 1878.1). 



