Colours of Wildlife: Oxyaena
Created | Updated Feb 5, 2017
Oxyaena
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!"
Another Prehistoric Special! This is good old Oxyaena lupina. Most of you will likely not be familiar with this one … I've known it since I was a young kid! Of course, I've never seen one. This species had been extinct for about forty-five million years already by the time the first humanoid-thingies turned up in Africa. But Oxyaena is very often illustrated in books about prehistoric critters, a wonderful example being the reconstruction painted by Czech artist Zdeněk Burian. I encountered that picture first at the age of seven or eight, in a lovely little book called 'Prehistoric Animals and Plants', a gift I got for Christmas from my parents, and still one of the all-time most exciting gifts I'd ever received. The painting shows a very cat-like Oxyaena clambering around in a tree. My own painting is an homage to that one though it's not as good. But I've tried to update the reconstruction: my Oxyaena is less cat-like, and a bit more like a weasel, marten or wolverine. The coat colour and pattern is of course entirely my own, speculative invention.
Ancient Meat-Eaters
The name 'Oxyaena' means 'sharp hyena'. Again, hyenas too are not at all closely related to it. Hyenas are close to cats in the modern 'Carnivora' order. Oxyaena was actually no close relative either to cats or to weasels, martens, wolverines or any surviving predatory mammals. It was part of a 'first experiment' in carnivorous mammalian designs. For long, it was considered to belong to a group called the 'creodonts'. Today, this group is no longer recognized … it is understood that paleontologists actually created the group by throwing together a bunch of early meat-eating mammals, even though they were not closely related to each other. Today, what used to be the creodonts, has been divided into two main groups: the Hyaeonodontids and their relatives, and the Oxyaenids and their relatives. Oxyaena has thus become the typical representative of the oxyaenids. They were mostly rather long-bodied and short-limbed, with long, stout tails, and short necks carrying heavy skulls with short, cat-like muzzles. Unlike modern cats, they didn't have retractile claws, and they walked with the entire palm of the front and back feet touching the ground, where cats walk only on their toes. They were thus likely slower than modern cats are, but with their clawed 'fingers' and toes they were probably good climbers.
The oxyaenids included species up to the size of a bear, and down to the size of a small cat. There was even a group that mimicked sabre-toothed cats! Oxyaena itself was pretty much in the middle, around the size of a large cat, or small leopard. Its fossils were found in North America, especially Colorado, dating back from about 56 to about 49 million years ago. This makes it part of the initial diversification of mammals after the extinction of the non-Avian dinosaurs, about 65 million years ago. After whatever disaster wiped the dinos out, the ecology of the whole Earth was out of whack. It took around ten million years for everything to stabilize and for new, complex and balanced food webs to evolve. By the time Oxyaena turned up, mammals had diversified greatly, and there were at least a few big species around, though nothing to match the giant dinosaurs. In North America, tropical forests were extensive, found up to latitudes that are today inside the Arctic circle! The whole world was much warmer then. In these forests there were large herbivores such as the Coryphodon, a species much like a rhino or hippo though not at all closely related to them. These were much too large for Oxyaena to have preyed on. But smaller mammals in the forests included the first horses, no larger than small dogs, and also small lemur- or monkey-like arboreal critters. Both of these might have been prey for old Oxyaena.
Another interesting thing about life back then is that the world was very similar all over. Most of the land was forested, grass not yet having evolved to be as efficient and widespread as it is today. Mammals were very diverse, but not yet quite as diverse as today, and all over the world, the forests were dominated by small and mostly unspecialized species. Birds were also starting to diverge. At least a few lines had become large, the biggest flightless species threatening to equal the recently-vanished dinosaurs … but for some reason, no actual birds could ever evolve to similar dimensions, and mammals overtook them to become dominant on land. But birds went on to rule the skies. Even back in Oxyaena's time, a great variety of birds lived in the forests and wetlands and along the continental shores.
While Oxyaena was found in North America, there was at the time a great similarity between the regions that are America and Europe today. Indeed, back then they adjoined. The North Atlantic Ocean was just a narrow seaway that didn't yet fully separate the two continents, so animals and plants could make it across. Very similar – sometimes identical – species were thus found in Europe and America. The plants found in these regions at the time, show a very close relationship to plants mostly found in the rainforests of Southeast Asia today. Such rainforest plants have slowly retreated out of the northern regions as the Earth's climate gradually cooled, the greatest retreat having happened with the Ice Ages which commenced a couple of million years ago and in the midst of which we technically still live.
As I said, Oxyaena represented an early experiment with carnivore design among the mammals. It and its kin were quite successful for many millions of years. But soon the first 'modern' carnivores turned up, these being small, weasel-like animals also living in the same forests. But they had some subtle, novel features of their skulls and brains, their teeth, and their limbs, which somehow gave them the edge. Gradually, the more primitive carnivores vanished, replaced and outdone by the new, advanced carnivorans.
Some paleontologists believe that, of all the mammals living today, the ones most closely related to Oxyaena and its relatives, are the pangolins! These being the sole surviving link to such a unique and ancient lineage, makes it even more important for us to conserve them.
