Judith River/White River Fossils
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Mammals from White River formation

Titanotheres, also known as Brontotheriums, are the largest animals found in the White River formation.  These mammals evolved rapidly from their Eocene origins, dramatically increasing in size until they reached nearly the size of today's elephant.  They bore a superficial resemblance to today's rhinoceros, but were actually more closely related to horses.  The horns at the front of the Titanothere's skull required strengthening of the skull, which is achieved by the upwards curve of the skull as in the Rhinoceros.  Titanotheres became extinct during the Oligocene at a time when the forests were turning to grasslands.

Titanotheres are Perissodactyls, odd toed ungulates.

Brontops

The different Titanothere genera of the Chadron formation are distinguished by the shape and size of their horns as well as the arch of their skull.  Animals with heavy horns tend to have a arched skull for strength.  It is thought that the females had smaller horns.

Bronto150.jpg (42029 bytes) Skull is 33" long; horns and scattered other places have reconstruction.
Bronto150a.jpg (36255 bytes) One zygomatic arch is missing.
Bront150.jpg (27992 bytes) Lower right jaw section is 18" long; contains three teeth.
bront_jaw_top.jpg (12336 bytes) Top view of right lower jaw, showing three teeth.  The tooth on the right is the last tooth at back of jaw.
Brontooth.jpg (20899 bytes) Last molar from right upper jaw.  The upper molars are twice as wide as the lower molars.

 

Formation: Chadron (White River)
Epoch: Early Oligocene, although recent studies suggest late Eocene
Size: Not quite as big as an Indian elephant.
 

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