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!"

It's time for a prehistoric horned critter again! But one with a difference. Here you have Ceratogaulus hatcheri, a most unusual rodent. In overall shape, it much resembles a marmot, groundhog or other modern digging species, but the weird thing of it is that it had horns on its rear snout area, just in front of its eyes. The two horns stand side by side, an unusual arrangement compared to modern mammals, but one that did feature in a few extinct species of large mammal. Ceratogaulus and close relatives were the only rodents known to have had horns, and are also the smallest known horned mammals. Ceratogaulus was fairly large for a rodent, its stocky body reaching 30 cm/12" in length, but still far smaller than the smallest living horned ungulates, the duikers and the dwarf antelopes of Africa.

It is high time I start featuring some prehistoric rodents here. I've already treated several living rodent species. Rodents can be considered the most successful order of mammals today – they constitute about 40% of known mammal species, and are present from the high Arctic to the great deserts to the tropical rainforests and include digging, swimming, scurrying, leaping, climbing and even gliding types. They range from tiny mice to the sheep-sized Capybara of South America, and some extinct forms were even larger. Rodents generally all possess enlarged, ever-growing front teeth they use for gnawing. Rabbits, hares and Pikas also have similar front teeth but are not rodents proper, instead belonging to a closely related order called the Lagomorpha. Rodents have a long evolutionary history, going back to the Palaeocene Epoch, the first of the 'Age of Mammals' after the extinction of the dinosaurs. Because rodents are generally small, most of their fossils are of isolated, scattered bones or teeth. Numerous skulls and bones and complete fossils of Ceratogaulus have been found, so we have a very good idea what it looked like.

Horned gophers were unique enough to have a family of their own, the Mylagaulidae. Not all members of the family had horns. Ceratogaulus was a very successful genus, living from about 16 million years ago, the Miocene, to about 5 million years ago, the Pliocene. It occurred in the Great Plains of North America, most fossils having been found in Nebraska. The earlier species were smaller in body and had small horns; the later species had horns up to 33 mm/1.3" in length. Its skull was short and sturdy; its eye sockets show that it had small eyes and likely poor vision. It had big, broad, spade-like front feet with long claws, excellent digging tools. Its tail was fairly short.

The closest living relative of the horned gopher is an enigmatic rodent called the Mountain Beaver or Sewellel, Aplodontia rufa, which occurs in the Pacific Northwest of America. Despite its name, the mountain beaver is not at all a beaver, but belongs to its own family, of which it is the last survivor. The horned gopher was in a different, but related family, now entirely extinct. They belonged to the same branch of the rodent family tree as the squirrels. Remember that marmots, groundhogs, prairie dogs and chipmunks are also all in the squirrel family. Beavers by contrast belong to a different branch, together with pocket gophers and kangaroo rats.

What were Ceratogaulus's horns for? If horns were useful as digging tools, we could expect to find many more horned rodent species, but we don't. Also, the position of the horns weren't right for digging: all digging mammals use their front paws and/or the tips of their snouts to dig, but the horns of Ceratogaulus were set far back. Horns might have been for display, but because the horned gopher had such small eyes, it's unlikely to have focused on any visual features. The horns were also not positioned right to enable males to fight each other using them. To 'lock horns' they would have to tilt their skulls downwards about 90 degrees, which would have been difficult or impossible with their short necks. As far as we know, both males and females had the horns, so they couldn't have been functional in just one of the sexes. All that remains is that the horns were used for defense. Since they lived below or low on the ground, most of their enemies would have come at them from above; the horns might have been a deterrence to these. They were situated so that they could have been used to defend the vulnerable skull and also the neck and upper back. The back of the skull was broad and suited to the attachment of strong neck muscles, so that the head and horns could be snapped upward and backward quickly and with force.

We don't know much about the lifestyle of these digging beasties. While they may have sheltered in tunnels and burrows, they perhaps came to the surface to graze and browse, during which times they would have been most exposed to predators. Sadly, when these strange rodents went extinct about five million years ago, they left behind no similar descendants. They were an isolated experiment in growing horns on rodents. Still, they show us again that evolution can accomplish some remarkable things. Horned rodents may yet turn up again in the future!

Willem

29.05.23 Front Page

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