Brontotherium (Greek for "thunder beast"); pronounced bron-toe-THEE-ree-um; also known as Megacerops
Plains of North America
Late Eocene-Early Oligocene (38-35 million years ago)
Size and Weight:
About 16 feet long and three tons
Large size; paired, blunt appendages on end of snout
About Brontotherium (Megacerops)
Brontotherium is one of those prehistoric megafauna mammals that has been "discovered" over and over again by generations of paleontologists, as a result of which it has been known by no less than four different names (the others are the equally impressive Megacerops, Brontops and Titanops). Lately, paleontologists have largely settled on Megacerops ("giant horned face"), but Brontotherium ("thunder beast") has proven more enduring with the general public - perhaps because it evokes a creature that has experienced its own share of naming issues, Brontosaurus.
The North American Brontotherium (or whatever you choose to call it) was very similar to its close contemporary, Embolotherium, albeit slightly bigger and sporting a different head display, which was larger in males than in females. Befitting its similarity to the dinosaurs that preceded it by tens of millions of years (most notably the hadrosaurs, or duck-billed dinosaurs), Brontotherium had an unusually small brain for its size. Technically, it was a perissodactyl (odd-toed ungulate), which places it in the same general family as prehistoric horses and tapirs, and there's some speculation that it may have figured on the lunch menu of the huge carnivorous mammal Andrewsarchus.
One other odd-toed ungulate to which Brontotherium bears a marked resemblance is the modern rhinoceros, to which the "thunder beast" was only distantly ancestral. Just like rhinos, though, Brontotherium males battled each other for the right to mate - one fossil specimen bears direct evidence of a healed rib injury, which could only have been inflicted by the twin nasal horns of another Brontotherium male. Sadly, along with its fellow "brontotheres," Brontotherium went extinct around the middle of the Cenozoic Era, 35 million years ago -possibly because of climate change and the dwindling of its accustomed food sources.