Colours of Wildlife: Megacerops

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Willem is a wildlife artist based in South Africa. He says "My aim is simply to express the beauty and wonder that is in Nature, and to heighten people's appreciation of plants, animals and the wilderness. Not everything I paint is African! Though I've never been there, I'm also fascinated by Asia and I've done paintings of Asian rhinos and birds as well. I may in future do some of European, Australian and American species too. I'm fascinated by wild things from all over the world! I mainly paint in watercolours. . . but actually many media including 'digital' paintings with the computer!"

Megacerops by Willem

At the end of 2020 I received a commission to draw illustrations of prehistoric animals for the Bishop Museum in Florida. They cooperate with palaeontologists in Nebraska, where they have diggings, and my pictures became part of an exhibition of their findings. There is also a virtual exhibition which you can see here:

Bishop Museum Exhibition

They feature my illustrations as well as line drawings of the skeletons of the animals as well as 3D scans of fossils which you can view at any angle. Please visit and click a lot!

And do check out the Bishop Museum as well. Go there, if you're in the area. The Bishop Museum of Science and Nature in Bradenton, Florida, is the largest natural and cultural history museum on Florida’s Gulf Coast. Its mission is to inspire the joy of discovery and wonder for all ages through excellence in stewardship and engagement.

The animal you see here, is the largest kind of mammal to have been found around Nebraska back then. Back when, you might ask? Well, the diggings cover a period on average about 35 million years ago, which was the transition from the end of the Eocene, the 'dawn of the recent', to the beginning of the Oligocene, the 'few (that is, not very) recent' period. This time during the Cenozoic, the 'Age of Mammals', featured a turnover of mammals from ancient to more modern types. Environmentally, over much of the world including North America, there was also a transition from moist, dense forests to drier, open grasslands. In this era, the Megacerops coloradensis ('huge horned face from Colorado') represented a more primitive type, destined not to survive the transition.

But old Megacerops cannot be considered an evolutionary failure by any means. The genus itself survived for over four million years, while the family it belonged to, the Brontotheriidae, flourished for over 20 million years, from the Palaeocene (which is a bit of an oxymoron meaning 'ancient recent') not long after the extinction of the non-avian dinosaurs, to the beginning of the Oligocene. The Brontotheres ('thunder beasts') were perissodactyls. This means they were relatives of our modern horses, tapirs and rhinoceroses. They do look rather rhinoceros-like, but they were actually a quite different group. Rhinoceros horns aren't bone, but rather, keratin, like hair and fingernails. Brontothere horns had bony cores and likely were covered in skin in life. Brontotheres had three toes on the hind feet, four on the front, while present-day rhinos have three toes on all feet. Brontothere skulls also differ in shape and structure from those of rhinoceroses. Their eyes were set well forward in their skulls, and their braincases were comparatively small. They seem to have had substantial lip and muzzle tissues in addition to the horns, which they could use for grasping plant leaves and stems as they ate. While modern rhinos are grazers or browsers of often-coarse material, brontotheres were unable to deal with tough food, and had to browse soft, juicy plants. They likely hung around moist landscapes such as forest clearings and edges close to marshes, rivers or floodplains.

Actually, brontotheres were more closely related to horses than to rhinos. The very first ones that appeared, were indeed small, light and very horse-like animals. Eotitanops ('dawn titan-face'), a representative early brontothere, stood only about half a metre/yard at the shoulder, with slender limbs, and a hornless, horse-like head. It lived in North America. Brontotheres very rapidly increased in size. By the late Eocene, genera like Megacerops, Rhinotitan ('titan-nose') and Embolotherium ('battering-ram beast') were comparable in size to elephants, reaching 2.5 m/8'2" at the shoulder hump, and weighing several tonnes. Though found in North America and East Asia, the group seems not to have made it to Europe or Africa.

Thus, brontotheres were among the first truly massive mammals to evolve. They were only rivalled by the giant horselike rhinos such as Paraceratherium, the giant unicorn rhino, and the Proboscideans, the elephants, mammoths, mastodons and their kin. During the heyday of the brontotheres, the first true rhinos and horses also evolved, but these remained small and light animals until well after the brontotheres' demise.

Thunder Horses

One of the last-surviving brontotheres, Megacerops is now represented by myriads of fossils of excellent preservation, found in plains regions of North America such as in Colorado, Nebraska and South Dakota. Their huge bones are frequently discovered after being exposed by landslides, floods or heavy rains. Native Americans of the Sioux tribes have been noticing them for long now, and feature them in legends and folk tales. They attribute the bones to great horse-like animals that live in the sky and fall to the ground during thunderstorms, the force of the crashing-down producing the sound of thunder. This is where the name for the group, brontotheres or thunder-beasts, comes from.

There is much variation in Megacerops fossils. Specifically, the size and the shape of the 'horns' on the snout. In some kinds, these amount to no more than two side-by-side bumps, while in others, there is a huge, forked and often flattened Y-shaped structure. There's even a kind, tentatively named Megacerops kuwagatarhinus, where each branch of the Y rebranches in turn towards the tips. In the past, not only many different species of Megacerops, but even several different genera, were described based on differently-shaped horns, such as Brontops, Menodus, Titanotherium and Brontotherium. Currently, all of these have been classified in Megacerops and a lot of the variation in the horn structure is attributed to sex and age differences.

What were the horns used for? In Megacerops's time, the first large mammalian predators came on the scene, such as Hyaenodon and the Terminator Pigs. While an adult Megacerops would have been too big for these to tackle, young ones would have been vulnerable, and the adults could use their horns to defend them. They also could have used the horns for displays and fights with other members of their own species. Indeed, at least one fossil has been found with broken rib bones that could have been the result of a hard blow from the horns of another Megacerops.

Other animals that lived during the time of Megacerops include an interesting mix of old and new types. Ancient forms were the brontotheres, hyaenodonts and the nimravids, a group that could be seen as early precursors of the cats. These all went extinct without descendants, but with similar-looking forms evolving from related groups: rhinos, wolves and hyenas, and true cats. An intermediate form of life was present in the form of the Oreodonts, strange sheep-or-pig-like herbivores that don't have any exact modern equivalents. Then there were the modern forms coming into existence: the first true horses and rhinos, camels, and the precursors of antelopes and deer. All of the modern types proved adaptable, and as the grasslands spread at the expense of the forests, they evolved into large, fast, long-legged types, able to flee or pursue prey over the vast new plains.

But the brontotheres were not as lucky. They failed to produce new types to keep pace with the changing times. In Asia as well as in America, they died out at the transition to the Oligocene, leaving only their enormous, intriguing bones behind.

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