106 



TITANOTHEEES OP ANCIENT WYOMING, DAKOTA, AND NEBRASKA 



origin of the Brule clay of the White River group and 

 to advance reasons for believing that the sandstones 

 were formed by river and flood-plain sedimentation 

 and the clays in part by back water and lagoon and 

 chiefly by eolian sedimentation. His paleontologic 



Porcupine Butte 

 CANIC ASH LAYER 



t-:<Wjg ,, 



"■""'saite-,,,. 



jifery'cocha 



Steneofiber 

 Prom erycoch ce 



Figure 73. — Panoramic section of the Big Badlands of South Dakota 



Modified from United States Geological Survey Bulletin 361, PI. in. (Osborn and Matthew, 1909.321.) View 

 southeastward from Cheyenne River, along line indicated on Figure 09, toward Porcupine Butte, across 

 the Chadron, Brule, and Arikaree formations. This section illustrates the intrusion of river-channel 

 deposits (the " T'/VaTioMfriiim sandstones," "JV/c/amyTiodon sandstones," and "Pro^ncfras sandstones") and plete skeletons at present knOWn maV 

 river-channel conglomerates in "clays" of the ritanof/iOTitm and Orfodoji zones. It shows also the charae- , j-j+ufi f 1^" 



teristic erosion forms of these different layers. (See map forming fig. 69, vicinity of section B.) be COUntcd On the nngerS 01 One nana. 



The Testudinata as analyzed by Hay (1908.1) 

 furnish evidence that during lower Oligocene time the 

 Great Plains region was prevailingly dry land. In 

 the sediments of the White River group there occur 

 eight species of the Testudinidae, including one of 

 the land tortoises, Stylemys, and one 

 species of Testudo. Testudo hrontops 

 Marsh occurs in the Titanotherium 

 zone (Chadron formation) and is 

 generally found in the White River 

 deposits of Colorado. Of water-living 

 forms the White River group of South 

 Dakota has furnished one species of 

 small turtles related to the Chelydridae 

 and now confined to Central America. 

 In 1904 Loomis (1904.1) advocated the 

 flood-plain origin of the "Titanotherium 

 beds" and described two new river-hv- 

 ing reptiles — Chrysemys, similar to the 

 Emys lativertehralis Cope of the 

 Wasatch; and Alligator prenasalis 

 (Loomis), recently found by Loomis 

 in the beds of Indian Draw, the first 

 appearance of this genus in the 

 Tertiary. 



The nature of the sandstone or the 

 clay in which their remains are found 

 makes it impossible to separate the 

 mammals of the Chadron formation 

 (Titanotherium zone) into plains- 

 dwelling and river-dwelling forms, 

 because during floods both were swept 

 into the streams, the skeletons being 

 dissociated and the skulls and jaws 

 separated. Doubtless also the remains 

 of decaying carcasses were pulled apart 

 by crocodiles and garpikes. Only three 

 complete skeletons with skulls have 

 been found intact, namely, the famous 

 Brontops rohustus of the Yale Museum, 

 the Brontops rohustus of the American 

 Museum, and the Menodus trigonoceras 

 of the Munich Museum. "For every 

 even approximately complete skele- 

 ton," observes Hatcher (1902.3, p. 

 124), "there are scores of isolated 

 skulls and other bones. Taking Titano- 

 therium as an example, I have myself 

 collected nearly 200 skulls of this 

 animal, while the number of fairly com- 



analysis showed that the fine Brule clays contain 

 chiefly terrestrial and plains animals, whereas the 

 river-channel sandstones that traverse these clays, 

 although contemporaneous, contain chiefly forest and 

 fluviatile animals. 



SOUTH DAKOTA IN TITANGTHEEIUM TIME 



The best description of the conditions in the South 

 Dakota region while it was inhabited by titanotheres 

 is that given by Hatcher (1902.3, pp. 125-127), 

 based on his own keen observations, which extended 



