Explosions, running... By golly, it's a Michael Bay movie!
They aren't rhinoceroses. They aren't freak deer on steroids. They're not a pronghorn or one of the synthetoceratids. No, they're brontotheres. They were what happened when the Eocene said, "You want your ceratopsians back? Well here they are!", followed by a cackling laugh. And in the geologically short 22 million year timeframe they inhabited, they proved to be one of the most fruitful families to have existed, with more than 40 genera currently described.
Brontotheres, once called titanotheres, got off to a humble start with the little guy at left. Eotitanops, standing only 18in, looks like something that'd be adored by girls worldwide due to how odd and "derpy" looking it is if was alive today. This isn't even fair how ridiculous it is. It's like someone crossed a donkey and a tapir. Anyways on to the real info. Eotitanops lived from the Early-Mid Eocene in North America and Asia, the Asian forms surviving the latest. This stocky little creature was a small browsing creature, rather similar to contemporary Hyracotherium. Also similar to its contemporary, it had four toes on the front feet and three toes on the hind feet. These feet would remain the staple of all brontotheres to come, no matter how big they got. And big they did get. But more on that later.
Sphenocoelus, shown at right under a synonymous name, represents a good specimen of the intermediate form between Eotitanops and later brontotheres. At 4ft tall at the withers, it was more than twice as tall as its ancestor above, weighing in the area of 234lbs. It almost resembled a small hornless rhinoceros, suited for cropping leaves as the rest of its family would until their extinction. Restricted to Wyoming and Utah, it didn't enjoy a huge range like its ancestor did. Also similar in appearance was Palaeosyops, a much larger beast the size of a cow. It too was found primarily in Wyoming, as many brontotheres seem to be.
Here there be monsters. Megacerops is the big daddy of brontotheres, the epitome, the zenith of the family. Recently, six genera have been sunk into Megacerops, and different species show different horn structure. M. coloradensis, shown at left had the classic Y-shaped horn. Or maybe it's a boomerang. Or a slingshot. Another species, formerly known as Brontops, had the splitting horn that quickly ended in two ball-shaped knobs. At 8.5ft tall at the shoulder, 4 tons, 16ft long, and with a 3ft skull, it was the largest of the family; a giant as big as an Asian elephant.
Another of the giant brontotheres to have occurred near the end of their reign was the Asian Embolotherium, only slightly smaller than its North American relative above. It seems to have been the only brontothere to have appeared in a documentary, shown in Walking with Beasts, also covered in Primeval when a herd escaped into modern times. Unlike many other species, there is no clear known sexual dimorphism in both species of Embolotherium (E. andrewsi, shown at right is distinguished by the heart-shaped end of the horn, E. grangeri had a more spoon-like end), contrary to the individuals presented in WWB. Due to the extremely large nasal cavities, some have suggested that the horn actually supported a nasal sac used for communication. Now that'd be something to see.
From small humble Eotitanops to giant Megacerops, brontotheres enjoyed a rich culmination in the Eocene. Alas their dentition was poor, constricting them to feed on leaves. When the grasslands of the Oligocene began replacing the forests of the Eocene, the brontotheres were surely doomed. They have been cursed throughout history was being dumb, clumsy, and slow-witted when in reality they would have been majestic beautiful creatures to observe in the wild. They've only been immortalized in media several times, a real shame. Here's to hoping some will remember the brontotheres in a brighter light.
Megacerops fleeing from volcano - Rod Ruth
Eotitanops - Dmitry Bodganov
Sphenocoelus - Roman Yevseyev
Megacerops pair - Dmitry Bodganov
Embolotherium - Steve Kirk
Family ensemble - Frederik Spindler
Funk & Wagnalls World of Dinosaurs and Other Prehistoric Animals
Prehistoric Times Issue 98
The Illustrated Encyclopedia of Dinosaurs & Prehistoric Creatures
National Geographic Prehistoric Animals