Size and Weight:
About Brontotherium (Megacerops):
Brontotherium is one of those prehistoric megafauna mammals that has been "discovered" over and over again by paleontologists, as a result of which it's been known by no less than four different names (the others are 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.
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 bigger 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.