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!"
Back in time we go yet again. Today I want to tell you a thing or two about Euceratherium collinum, the 'True-horned Beast of the Hills'. It is often given the name Shrub Ox. But it's not an ox! Nor is it a buffalo or a bison. Instead, it is closely related to the sheep and goats of today. You might call it a giant, ox-like sheep. Which isn't actually that strange, since we do have a giant, ox-like sheep with us still – the Musk Ox! I will hopefully soon write something about that great big shaggy beast. But when we go back in time, we see that musk oxen have indeed a long slew of relatives and ancestors of various sizes and shapes, with Euceratherium being one of them.
Now for some even wider context. Today we have lots of hoofed mammals in the world. There are the horses, zebras and donkeys, with just a single hoof per foot; they're related to rhinos and tapirs, who have three (or in the case of the front feet of tapirs, four) hooves per foot. The group is often called the uneven-toed hoofed mammals, and their order is the Perissodactyla. They are not at all closely related to the other grouped of hoofed mammals, which generally have an even number of hooves (that is to say two or four) per foot, the Artiodactyla. The Artiodactyla is a much larger group. It includes everything from hippos through camels to giraffes to deer and antelopes. It even includes the whales and dolphins! Even though they no longer have hooves, they're actually descended from a very early group of even-toed hoofed mammals and developed their radical specialisations for a swimming life over a surprisingly short (by evolutionary standards) time period.
Now let us zoom in closer on the artiodactyl family tree. One group in particular is our concern: the group technically known as the Bovidae. Now this group today includes a huge diversity of forms. There are the antelopes of Africa and Asia, the cattle, buffaloes and bison, the sheep, the goats, and a bunch of things not very easy to classify precisely. They do have some features in common. All of them have horns (except for the females of some of the species) of a particular configuration. The horns are supported by extensions from the skull, usually two (but in one modern species, four) growing from the top of the skull. These bony horn cores are covered in a growth of horn tissue, or keratin, called the horn sheath. The horn sheath can much extend the size of the horns beyond the bony horn core. Bovid horns are never branched or shed, like those of deer. They're never covered with skin and hair, like those of giraffes. The many species of bovids, despite their differences, all conform to that pattern. And that simple pattern has in fact allowed an amazing diversity of different kinds of horns to come into existence. The bovid family as a whole has blossomed into great diversity, and today is close to its heyday. It is an evolutionarily-young family, having its origins mainly in the Miocene, dating back to about twenty million years.
Bovids initially were animals of Africa, Europe and Asia. They entered North America starting around the late Pliocene, two million or so years ago. These included the ancestors of today's American bovids: the bison, the two species of wild sheep, and the wild goat (which is actually closer to the Chamois of Europe than to domestic goats and wild ibexes). And then there were these! Euceratherium, the shrub ox, was like a precursor for the present-day musk ox. It was not yet as highly specialized. The modern musk ox is adapted for the often extremely cold and barren tundra region of the far north. The shrub ox lived in more lush and temperate environs. Its fossils come from much of North America as far south as Mexico. Even during the Ice Ages, the southern portions of this range were still quite hospitable. The shrub ox probably had shaggy hair, but not as long as that of the musk ox. It was slightly bigger than the musk ox, reaching a bodyweight of 600 kg/1300 lbs, with longer legs and body. As reflected in its names, it seems to have inhabited hilly terrain, and browsed upon a variety of trees and shrubs.
The shrub ox's head-weapons still resembled those of many kinds of large-horned sheep. They were thick at the base, curving backward and outward, then forward and upward, and the horn cores suggest that the horns themselves could have reached an impressive length. Perhaps the shrub oxen also bumped their horns together as some wild sheep and musk oxen do today during fights for dominance and females. But the horns were also well-suited to defense. At the time, a variety of large predators inhabited North America, including American lions, giant short-faced bears, and sabre-toothed 'tigers'. Over the course of the shrub-ox's existence, there were also dramatic climate fluctuations in which glaciers and ice sheets spread and retreated repeatedly. It was quite a perilous environment. Nevertheless, the shrub ox flourished from about 1,8 million to 12 thousand years ago, which is a decent reign. It's not clear why it became extinct. There were several other mux ox relatives present in America: a giant 'precursor-musk-ox', Praeovibos; Soergel's Ox, Soergelia; and the Woodland Musk Ox, Bootherium. These are all extinct now, leaving only the musk ox, which occurs in the far north of Europe, Asia and North America. Amazingly however, there was one musk ox relative that made it all the way to Southern Africa – the Makapan Musk Ox, Makapania. I'm going to try to locate fossils of this one – there must be some in a museum somewhere in my country – so I could tell its story.