336 



TITANOTHERES OF ANCIENT WYOMING, DAKOTA, AND NEBRASKA 



P. grangeri may be a descendant of some large 

 strain of P. major, such as Am. Mus. 13116; in fact, 

 very projecting parastyles are seen in Am. Mus. 

 12185, transitional between the P. leidyi and the 

 P. major stage, and also in Am. Mus. 12680, from B 5, 

 referred provisionally to P. paludosus. 



The species is especially distinguished by the 

 extremely prominent parastyles of the niolar teeth, 

 which result in the very oblique direction of the 

 ectoloph. The principal measurements are, p'-m^ 

 180 millimeters, breadth of p* 31, of m^ 43, oblique or 

 diagonal measurement of m' 57. The grinding teeth 

 form a continuous series behind the large and laterally 

 compressed canines. The single incisor preserved 

 exhibits a subcaniform crown, 20 millimeters in 

 height; the mesostyles are not observable on p^ or p'' 

 but were possibly present (though small) in the 

 unworn condition. The molars exhibit sharply defined 

 median ridges in the valleys of the ectolophs. Strong 

 development of the cingulum, which surrounds the 

 entire crown excepting only the inner sides of the 

 protocones, is a very characteristic feature. The 

 conules are also well developed but relatively less 

 than in typical specimens of P. roiustus. In p^ the 

 internal cingulum is complete though faint. 



The fragment of the lower jaw which has been 

 preserved (fig. 284) indicates that the thickening of 

 the lower border which we have traced in successive 

 stages from P. major is now carried back below m.3. 

 The ramus measures 86 millimeters below m^; mi_3 

 estimated at 126 millimeters. The anterior lobe of 

 nis measures 31 millimeters transversely. This tooth 

 has strongly striated sides, festooned external cingula, 

 and strong entoconules. 



Palaeosyops copei Osborn 



Plate LX; text figures 120, 266, 267, 281, 484, 511-514, 519, 

 543, 547-550, 724 



For original description and type references see p. 181. For skeletal characters 

 see p. 629] 



Type locality and geologic Tiorizon. — Henrys Fork, 

 Lone Tree, Bridger Basin, Wyo.; Bridger formation, 

 Vintatherium- Manteoceras- MesatirM.nus zone, level 

 Bridger D 3. Probably also from level A of Washakie 

 Basin, Wyo. 



Specific characters. — Tooth row of somewhat smaller 

 size. The most progressive species of Palaeosyops 

 known in superior premolar and molar evolution. 

 Heavy cingula embracing the inner sides of the 

 crowns. P*, p', p^ very advanced, with subquadrate 

 contours and subequal protocones and tritocones, in- 

 cipient tetartocones on p*, and distinct tetartocone 

 constriction on p^ (rectigradations). 



This little-known animal represents a most ad- 

 vanced stage. It is, so far as known, the terminal 

 stage of Palaeosyops evolution. In view of its pro- 

 gressive character this species is appropriately named 

 in honor of Edward D. Cope, one of the founders of 



American vertebrate paleontology and the describer 

 of Lambdotheriura, "Palaeosyops" horealis, and other 

 species of Eocene titanotheres. 



Materials. — This species is positively known only 

 from the American Museum series of superior grinding 

 teeth (No. 11708) from Lone Tree, Henrys Fork, 

 Bridger level D 3, including the premolars and molars 

 of opposite sides (PL LX; fig. 120). Detailed meas- 

 urements are given above. As shown in Plate LX 

 this is by far the most specialized or advanced of the 

 species of Palaeosyops in respect to the molarization 

 of the premolars. It shows the following features: 

 (1) The cingida are carried broadly around the inner 

 sides of p'""*, a character approached but not so fully 

 attained in any of the previous stages of the evolution 

 of the premolar teeth of this genus; (2) a rudimentary 

 tetartocone is present on p^, as indicated by a con- 

 striction of the deuterocone to form this cusp, very 

 apparent on the outer side of the deuterocone and less 

 strongly marked on the inner side; (3) the decided 

 convexity of the protocone and tritocone ridges of 

 the ectoloph approaches that of some of the uppermost 

 Eocene titanotheres and is quite different from that in 

 P. rohustus or P. leidyi; (4) p^ is a very progressive 

 elongate tooth (17 mm. as compared with 12 in P. 

 leidyi), with rudimentary deuterocone; (5) the molar 

 cingula are very broad and heavy, continuous around 

 the inner side of the protocone in m^; (6) the inner 

 side of all the premolars is more filled out, more sub- 

 quadrate. 



P. copei is also very probably represented in Washa- 

 kie A by Am. Mus. 13177, a very aged skull, in which 

 the teeth, so far as preserved, closely resemble those 

 of the type but are a little larger. Portions of the 

 skull indicate an animal about the size of the P. 

 leidyi type, resembling the leidyi-rolustus group in 

 its very convex forehead, nasals, and basicranial re- 

 gion. The nasofrontal horn swelling was if anything 

 more pronounced than in P. rohustus. The nasal 

 sinus beneath the horn, so prominently developed in 

 Oligocene titanotheres, was present. 



A specimen doubtfully referred to P. copei? is the 

 young jaw (Am. Mus. 12205a, level Bridger D 1) 

 that belongs with the cranium and skeleton described 

 on page 629. The associated top of the cranium 

 (fig. 281) is almost certainly that of a Palaeosyops, 

 but the specific reference is uncertain. In the jaw of 

 this specimen (fig. 266, B) the measurement from the 

 angle to the incisive border is 340 millimeters; p2-m3, 

 172. The second and third incisors are approximately 

 equal in size. The canine is comparatively small and 

 probably indicates that this animal is a female. Close 

 behind it is pi, followed by a narrow diastema (5 mm.). 

 P2 and Pa are very narrow, simple teeth, but slightly 

 more progressive than in Limnohyops prisons, the 

 metaconid being quite distinctly formed on the inner 

 side of ps. P4 is decidedly more progressive than that 



