EVOLUTION OF THE SKULL AND TEETH OF EOCENE TITANOTHEKES 



359 



of Doctor Wortman as seemingly different from any 

 previously discovered. He described them in a letter 

 written to Professor Osborn from the field as exhibit- 

 ing rudimentary horns at the junction of the f rentals 

 and nasals and suggested the generic name Manteo- 

 ceras or "prophet horn." On the arrival of these 

 skulls at the American Museum Professor Cope, the 

 writer, and others who examined them expressed 

 great doubt as to whether the tuberosities (PI. XVI; 

 figs. 305, 307) above the orbits could really be re- 

 garded as incipient horns. These doubts were soon 

 removed by the discovery of similar horns in Dolicho- 

 rhinus cornutus { = 'hyognathus) of the middle Uinta, 

 an^ Doctor Wortman's observation was thus verified. 



As detailed in Chapter III (p. 151) the animal was 

 first identified by Osborn with the imperfect upper 

 CO type teeth of the species Palaeosyops (Telmatherium) 

 vallidens Cope, previously found by Professor Cope in 

 the Washakie Basin; but it was subsequently ascer- 

 tained that this species, now provisionally referred to 

 the genus DolichorTiinus, belongs in a higher level, 

 Washakie B, whereas the types of Manteoceras man- 

 teoceras were both found in Washakie A. 



These animals {M. manteoceras) were first supposed 

 to be confined to the lower levels of the Washakie 

 Basin, but subsequent exploration of the upper 

 Bridger by the American Museum expeditions has 

 proved that they were still more numerous in the 

 Bridger Basin; altogether the remains of more than 

 twenty animals of the type species (M. manteoceras) 

 have been found by the American Museum parties, 

 including seven skulls in Bridger D and four skulls in 

 Washakie A. In the upper levels of horizon A of the 

 Washakie Basin a more advanced stage has been 

 found, M. washaJciensis. Thus far these animals have 

 not been found in the Uinta Basin in beds of level B, 

 deposited during a period when they undoubtedly 

 lived; but in the lower part of Uinta C the genus reap- 

 pears in the important species described by Douglass 

 as Manteoceras uintensis. In the lower part of Uinta 

 C an animal nearly related to Manteoceras, if not its 

 direct successor, was discovered by the Princeton 

 expedition in 1894 and was subsequently recognized 

 by Hatcher as probably a successor of Manteoceras, 

 and named by him ProtitanotTierium emarginatum. 



Geologic distribution. — The geologic levels at which 

 the remains of these animals have been found are 

 shown in Figure 334, and as the remains are numerous 

 in the upper Bridger, levels C and D, and in the lower 

 Washakie, level A, they indicate that these deposits 

 are contemporaneous. As observed in the text on 

 Telmatherium, the advent of Manteoceras appears to 

 have been contemporaneous with the last stage in the 

 development of the Palaeosyops-Limnohyops phylum 

 and with the first appearance of the Mesatirhinus- 

 Dolichorhinus phylum. The abundance of remains of 

 these animals in the upper Bridger deposits is very 

 101959— 29— VOL 1 26 



striking. It is possible that they are represented also 

 by skeletal remains in the lower Bridger. 



Affinities to other Eocene titanotheres. — The resem- 

 blances and contrasts between Manteoceras and Tel- 

 matherium have been pointed out in some detail in the 



JDolicTzorh in us 



A^anteoceras 

 Figure 302. — Skulls of titanotheres of the 

 Manieoceras-Dolichorhinus group 



One-eighth natural size. A, Manteoceras manteoceras, middle 

 Eocene of Bridger Basin. Wyo.; upper Bridger. B, Mesati- 

 rhinus petersoni, middle Eocene of Bridger Basin, Wyo.; upper 

 Bridger. C, Melarhinus earlei, middle Eocene of Washakie 

 Basin, Wyo.; summit of Washakie A. D, Bolichorhinus hyo- 

 Snaihus, middle Eocene of Uinta Basin, Utah; Uinta B 2. 



descriptions of Telmafherium. They may also be very 

 clearly seen by comparing the crania of the types of 

 these two general (figs. 210, 219). To summarize 

 Manteoceras is distinguished from Telmatherium by (1) 

 deeper facial concavities; (2) much more prominent 



