662 



TITANOTHERES OF ANCIENT WYOMING, DAKOTA, AND NEBRASKA 



Mts II: Millimeters 



Length 150 



Transverse diameter at head 28 



Transverse diameter of shaft, median region 21 



Transverse diameter of distal end 26 



Mts IV: 



Length 41 



Transverse diameter of head 38 



Transverse diameter of shaft, median region 22 



Transverse diameter of distal end 34 



The restoration of Eotitanotherium osborni here attempted 

 (PI. X) is obtained from the material described in the preceding 

 pages, and it is chiefly based on two individuals. As previously 

 stated, the front of the skull, the lower jaws, atlas, axis, pelvis, 

 and a few fragments of the feet pertain to one individual, the 

 type, while the rest of the vertebral column, a few ribs and 

 limb bones, as well as a number of foot bones, belong to a 

 second individual, one of the paratypes.** The dotted hnes 

 represent estimated diameters and are consequently conjectural 

 as to proper contour outlines. This is especially true of the 

 posterior portion of the skull, the sacrum, the ischium, the 

 upper half of the femur, and the caudal region. There are 

 inserted two cervicals, two dorsals, the sacrum, and the greater 

 part of the caudal region. The vertebral formula as repre- 

 sented in the illustration is the same as that of the articulated 

 skeleton of Menodus from the Oligocene now in the Carnegie 

 Museum. The vertebral formula of Eotitanotherium osborni is 

 in part therefore tentative and is as follows: Cervicals 7, dorsals 

 17, lumbars 3, sacrals 4, caudals 18. The ribs are conjectural. 



Tlie illustration is effected for the purpose of ascertaining at 

 a glance the general proportions of the animal. Each part 

 represented by the solid lines is drawn directly from the bones 

 themselves, by the assistance of the pantograph, and the illus- 

 tration as a whole is fairly reliable. 



Measurements 



Centimeters 



Total length of the vertebral column from the premaxillary 

 to the end of the sacrum, all curves of the backbone in- 

 cluded 252 



Height of skeleton at fore limb 138 



Height of skeleton at hind limb 114 



SECTION 5. THE POSTCRANIAL SKELETON OF 

 OLIGOCENE TITANOTHERES 



Five factors have conspired to limit our knowledge 

 of the postcranial skeleton of Oligocene titanotheres 

 and to make it unsatisfactory. 



First, owing to the conditions of preservation and 

 deposition, the skulls of Oligocene titanotheres are 

 rarely found in association with the rest of the skeleton, 

 so that only a few skeletons have been mounted. 

 Marsh's type of Brontops robustus in the Yale Museum 

 and the skeleton of Menodus trigonoceras in the Munich 

 Museum are nearly complete. The skeleton of Bron- 

 tops dispar in the Carnegie Museum is nearly com- 

 plete, but it lacks the skull. The skeleton of Bron- 

 tops roiustus in the American Museum includes the 

 skull, fore limbs, and thorax of one individual, but the 

 pelvis and hind limbs are supplied from another 

 individual. "'' A few skulls were found in association 



" There was no other material found with the remains of Eotitanotherium described 

 in the preceding pages, except a few fragments of turtles. All the material was found 

 within a radius of about 20 feet. 



"« Since this was written the Colorado Museum of Natural History, at Denver, 

 Colo., has mounted an unusually fine skeleton of Megacerops acer, and the U. S. 

 National Museum, at Washington, has mounted'a partial skeleton of Brontottterium 

 haicheri. 



with parts of the limbs or of the backbone, but by 

 far the greater part of the collections consist of unas- 

 sociated skulls, jaws, and parts of skeletons. 



Second, the natural scarcity of well-associated 

 material was intensified by the hasty methods of 

 early collectors, who, with certain exceptions, through 

 eagerness to secure the conspicuous and highly 

 prized skulls, neglected the opportunity to collect 

 skulls and skeletal parts in association or failed to 

 make careful records of such association. Still further 

 damage was done through crude methods of packing 

 and transportation. 



Third, an unfavorable condition arises from the 

 crushing and distortion suffered by the skeletal parts 

 of titanotheres during the structural alteration and 

 displacement of the ancient strata in which they are 

 entombed. A skeleton in the American Museum of 

 Natural History (No. 1064), in which there is a good 

 association of dentition, vertebrae, and limbs, is 

 rendered practically useless for systematic study 

 through the crushed condition of the bones. Such 

 distortion often alters the natural contours and pro- 

 portions in a deceptive manner, as noted by the late 

 J. B. Hatcher (1902.1), who showed that in the Car- 

 negie Museum skeleton certain limb bones on one 

 side were much lengthened, whUe on the opposite side 

 the corresponding elements were shortened, the former 

 having been crushed laterally, the latter longitudi- 

 nally. As a result of distortion, added to the gr^at 

 difficulty of securing uniformity in the methods of 

 measuring such large skeletons, it follows that many 

 of the measurements given below would hardly be a 

 safe basis for precise quantitative distinctions between 

 supposedly different species. 



Fourth, a difficulty arises from the wide differences 

 between males, females, and young of the same species 

 and at different ages, which even in the study of well- 

 preserved skulls causes considerable uncertainty as to 

 the correct identification of certain specimens. Be- 

 sides this it is probable that fully adult male titano- 

 theres of the same species would show considerable 

 variation in minor characters and measurements of 

 the vertebrae and limbs, as in the case of modern 

 rhinoceroses. 



Fifth, the postcranial skeleton of titanotheres has 

 not hitherto been used to any extent by authors in 

 defining the genera and species, so that, from a 

 systematic point of view, the vertebrae and limbs have 

 not been regarded as sufficiently important to require 

 the degree of intensive study which has been made of 

 the skull and dentition. 



As a result of these unfavorable conditions we have as 

 yet only an incomplete knowledge of the generic char- 

 acters of the vertebrae and limbs of Oligocene titano- 

 theres, while we have hardly begun to recognize specific 

 differences. The following studies are preliminary and 

 should be supplemented by a more systematic and 

 intensive study of the material available comparable 

 with that which has been made upon the skulls. 



