374 



TITANOTHERES OF ANCIENT WYOMING, DAKOTA, AND NEBRASKA 



the relations of width to length thus being width 360, 

 length 555. The reference to Manteoceras is con- 

 firmed by the obliquely flattened form of the infra- 

 orbital portion of the malars, a character by which 

 this animal may readily be distinguished from the con- 



FiGURE 313. — Upper canines and incisors of Manteo- 

 ceras uintensis 

 One-haU natural size. Carnegie Mus. 2388 (type). "About 5 miles 



northeast of well 2, Uinta Basin; from gray sandstone in red Uinta 



beds, lower portion of horizon C." 



ttemporary Telmatherium ultimum, 

 though there is no infraorbital shelf. 

 The proportions of this part of the 

 skull indicate an elongation of the 

 facial region (as in M. uintensis), a 

 feature certainly not charateristic of 

 the line leading to Protitanoiherium. 

 The animal is undoubtedly a fe- 

 male, as indicated by the relatively 

 small canine teeth. 



A lower jaw (Am. Mus. 2033, fig. 

 310, C) found in the same region 

 and at first referred to Telmatherium 

 ultimum (cf. above) agrees in size 

 with this specimen. It also belongs 

 to a female animal and is of the 

 mesaticephalic rather than dolicho- 

 cephalic or brachycephalic type. The canines are 

 relatively small and recurved. M3 is a relatively 

 short (63 mm.) rather than elongate tooth as in 

 Telmatherium ultimum (76 mm.). 



Protitanotherium 



General characters. — In their phylogeny the animals 

 known as Protitanotherium are among the most 

 interesting of the titanotheres that lived in the Uinta 

 Basin, because of their evident relationship to Man- 

 teoceras on the ancestral side and to Brontops and 

 other Oligocene titanotheres on the descendant side. 

 The profile figure of the horn region of Manteoceras 

 manteoceras, P. emarginatum, two young skulls of the 

 Oligocene Brontops hrachycephalus, Allops marshi, 

 and Brontops rohustus illustrates the resemblance 

 (fig. 712). 



These upper Eocene animals are robust, massive, 

 vigorous, and well protected both by their powerful 

 tusks and by their rapidly developing horns, which 

 are far more prominent than those of any of the earlier 

 Eocene titanotheres. Therefore the suggestion of 

 Hatcher (1895.1, p. 1084) that this animal should be 

 called Protitanotherium was eminently appropriate. 



Progressive characters. — The phyletic increase in 

 size of the animals of this series is best illustrated by 

 comparison of the adult jaws of M. manteoceras, P 

 emarginatum, and P. superbum (figs. 310, 315, 321). 

 The preservation of the ancestral phyletic character 

 in these jaws is certainly very striking. The change 

 is chiefly proportional, or quantitative. The differen- 

 tial or generic distinctions are to be found especially 

 in the teeth and in the horns. 



Specific stages. — These protitanotheres are known 

 to include two stages — (1) P. emarginatum Hatcher, 

 originally described as Diplacodon emarginatum, found 



'y 



Figure 314. — Restoration of Protitanotherium emarginatum 

 By Charles E. Knight. About one-ninth natural size. 



near the base of Uinta C, or the "Diplacodon beds" 

 of Marsh, and distinguished from the following stage 

 chiefly by its inferior size and more brachyodont 

 teeth, and (2) P. superbum Osborn, a much larger 

 animal, whose remains were probably found at a 

 higher geologic level. 



Horns. — The bases of the horns preserve the Eocene 

 anteroposterior elongation. This elongate oval form 

 is in marked contrast to the obliquely oval, triangular, 

 or transversely elongate form of adult Oligocene 

 titanotheres. In very young Oligocene titanotheres, 

 however, the resemblance in the elongate oval horn 

 swellings to those of Protitanotherium is very noticeable 

 (fig. 374). 



Size. — In the species P. superbum these animals 

 attain a size considerably surpassing that of many 

 of the smaller forms in the lower Oligocene levels. 



