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!"

We go back in time once again, to the Miocene Period. Just a brief bit of info about these periods: the dinosaurs went extinct at the end of the Cretaceous, about 65 million years ago, and this heralded the start of the 'Age of Mammals' during which mammals and birds dominated ecosystems on land. This age is more properly called the Cenozoic, or the age of 'recent life'. The first period of this age was the Palaeocene ('ancient-recent'), followed by the Eocene ('dawn-recent'), and then the Oligocene ('few-recent'). These three periods are considered the time of the more ancient forms of mammal. They were followed by the three periods characterized by quite modern types of mammal, the Miocene ('less-recent'), the Pliocene ('more-recent'), and the Pleistocene ('most-recent'). The Miocene and Pliocene both featured mammalian life more diverse than what exists today; the Pleistocene saw the coming of the ice ages leading to many extinctions, while the arrival of humans caused the extinction of many more. Some scientists consider the time in which we are living as still part of the Pleistocene, but others consider it a new period, the Holocene ('all-recent') or Anthropocene ('human-recent'), a time in which our own existence will have an effect on Life on Earth that is so drastic that it might be considered a new era of evolution.

But our featured critter hails from South America in the middle of the Miocene, about 17.5-15.5 million years ago. It is Cladosictis patagonica. As always, I base its body shape on its known skeletal parts, while its coloration comes from my own imagination. Here you see it stealing an egg from a ground-nesting bird. Cladosictis was a Sparassodont, related to the ones I've dealt with here before, Borhyaena and Thylacosmilus. It shows a bit more of the diversity of forms found among the sparassodonts, which included types from small to large. If you don't want to read the other articles, let me just briefly explain that the sparassodonts were a group of carnivorous mammals that evolved in South America over its time as an 'island continent' disconnected from North America and Africa, but perhaps at least for some time connected with Antarctica, with which it shared some plant and animal forms. The sparassodonts were the dominant mammalian predators on South America until about three million years ago. They seem to have died out then, prior to the completion of the land bridge that linked South and North America, allowing 'modern' carnivorans like cats, dogs/wolves/foxes, bears and mustelids (weasels, martens, skunks, otters and so forth) to enter. All the carnivorous placental mammals now found in South America are descended from these northern immigrants. Sparassodonts formed a sister-group to the marsupials, which still remain diverse in South America and with a single species that managed to colonize North America.

Cladosictis was rather small, with a head-and-body length of about 80 cm/32" and a shoulder height of 20-25 cm/8"-10". It likely reached about 8 kg/17.5 lbs in weight. Its proportions recall a modern mustelid such as an otter or the Tayra of South America, with a long body and neck and short limbs. Its tail was fairly long. It had a long, low skull as well. Its dentition shows that it was mainly a carnivore, but might have included small amounts of plant material such as fruit in its diet. It had nimble digits with a 'thumb' that could be partially opposed to the 'fingers', giving it the ability to grasp prey, to manipulate objects, and to climb in trees or shrubs. It likely lived in forest, woodland or bushland, where concealment would protect it against larger predators while also helping it sneak up on its victims.

It is not known why this versatile little predator became extinct. Some of its fossils show strange bony growths on the jaws that in the most severe cases might have displaced several teeth. The cause of this malformation is not known, but might have been some kind of cancer or bacterial infection. The factor of disease in causing or contributing to extinction is one that hasn't been given much thought in evolutionary science, but it is something we might be looking at more closely. The sparassodonts, which were very successful for many millions of years, died out around 3 million years ago in the absence of any competitors or any kind of environmental or ecological changes that might have explained it.

Willem

25.05.20 Front Page

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