288 



TITANOTHERES OF ANCIENT WYOMING, DAKOTA, AND NEBRASKA 



With these specimens (association doubtful) were 



found the calcaneum, portion of a tibia, and a proximal 



phalanx. 



Lambdotherium magnum Osborn 



Text figures 154, 240 

 [For original description and type references see p. 199] 



Type locality and geologic horizon. — Huerfano Park, 

 Colo.; lower horizon of the Huerfano formation, 

 Lamidotherium-Eotitanops-Coryphodon zone (Huerfano 

 A). 



Specific characters. — Osborn writes: 



Exceeding in size any other known lambdothere is the type 

 jaw (Am. Mus. 17527) from the Garcia Canyon, lower Huer- 



FiGUKE 241. — Lower jaw and teeth of Lambdotherium progressum 



Natural size. Am. Mus. 14917, type, reversed; Alkali Creek, Buck Spring; Wind 

 River formation. 



fano, containing a complete inferior series, P2-m3 of both sides, 

 represented in Figure 240. These teeth exceed in length over 

 all (74 mm.) those of the type of L. popoagicum, in which the 

 same teeth measure 69. P3 has a rudimentary metaconid and 

 paraconid, in the same stage of evolution as in L. popoagicum. 

 Of similar large size is a referred specimen, Am. Mus. 15600 

 (fig. 240), from the Big Horn, west end of Tatman Mountain. 

 These referred grinders, m', m^, coincide closely in size with 

 the type of L. magnum and may be regarded as a paratype. 



Below are given the measurements of teeth of 

 species of lambdotheres. The numbers following the 

 specific names are those assigned to the specimens in 

 the American Museum of Natural History. 



Measurements of teeth of lambdotheres 



INIillimeters 



P2-m3; Huerfano A, L. priscum 17526 (referred) 67 



Wind River B, L. popoagicum 4863 (type) 69 



Wind River B, L. progressum 14917 (type) (esti- 

 mated) 71 



Huerfano A, L. magnum 17527 (type) 74 



M'-m^ :Huerfano A, L. priscum 17529 (referred) 21.5 



Huerfano A, L. priscMTO 2688 (referred) 22.5 



Huerfano A, L. progressum 17530 (referred) 23.5 



Wind River B, L. popoagicum 14902 (referred) _. 25 



Wind River B, L. magnum 15600 (referred) 27.5 



These measurements show that there is not a great 

 range in size between the smaller and the larger animals 

 referred to this genus (Osborn, 1919.494). 



Subfamily Eotitanopinae Osborn 



Lower Eocene titanotheres of intermediate size. 

 Body proportions slender, submediportal rather than 

 cursorial. Skull dolichocephalic; facial region longer 

 than cranial region. Superior molars brachyodont; 



molar tooth proportions much as in the Palaeosyopinae, 

 with reduced paraconules and metaconules. Inferior 

 molars without metastylids. Premolars j- present; 

 molarization of premolars retarded. 



Discovery. — The details of the discovery of Eoti- 

 tanops {Palaeosyops horealis) in 1850 and the early 

 history of opinion are in part related above. In 

 Cope's "Tertiary Vertebrata" (1885.1, p. 703, pi. 

 58a, fig. 3) a full description is given of the type molar 

 teeth and the imperfect radii of the animal that Cope 

 called Palaeosyops horealis (Am. Mus. 4892). 



Materials. — In 1891 Dr. J. L. Wortman, who had 

 discovered the type, enlarged our knowledge of this 

 genus by the discovery of another specimen (Am. Mus. 

 296), including a complete lower jaw, two cervical, 

 three dorsal, and one caudal vertebra, the femur, 

 humerus, and the greater part of the fore foot. These 

 bones were described by Osborn and Wortman in 

 1892 (1892.67) and were referred to the type species, 

 Palaeosyops horealis; they are now known as E. 

 princeps. 



Soon afterward Earle's memoir (1892.1) appeared, 

 in which he treated Palaeosyops horealis as probably 

 ancestral to the Bridger Telmatherium cultridens. In 

 1908 Osborn (1908. 318) revised" the Eocene titano- 

 theres and placed P. horealis in the new genus 

 Eotitanops. 



Granger's explorations in 1909 to 1911 resulted in 

 the discovery of the type of E. gregoryi and have 

 enabled us to make a systematic revision of these 

 animals based upon materials in the American 

 Museum collections, which are arranged below accord- 

 ing to size and morphologic succession; their geologic 

 succession is sho\vn in Figure 48. The numbers are 



AM.I7S30 



Figure 242. — Upper teeth of Lambdotherium 

 progressum 



Am. Mus. 17530, refened specimen from Huerfano A. Natural 

 size. After Osborn, 1919. 



those assigned to the specimens in the American 

 Museum of Natural History. 



E. major Osborn, 14894 (type), a third metatarsal of the 

 left side (figs. 145, 506). 



E. princeps Osborn, 296 (type), jaw, manus, humerus, femur, 

 etc. (figs. 144, 231, 246, 252, 484, 490, 494, 496, 498-600, 512, 

 686, 692, 700, 724 (Pis. XXVI, LIV). 



E. princeps Osborn, 4902 (referred?), fragments of pes. 



E. borealis (Cope), 4892 (type), superior molars p<-m^ radius, 

 etc. (figs. 102, 497, 498; PI. LIV). 



E. borealis (Cope), 14887 (neotype), skull, jaw, atlas, pelvis, 

 etc. (figs. 229, 232, 244, 250, 251, 494, 495, 501, 515, 721; PI. 

 LIV). 



