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!"

So. I might have mentioned this here or not, but I'm currently working on an enormous project, a book going in depth into the history of Life on Earth. The finished product will have thousands of illustrations; I've already finished hundreds. Most will be monochrome drawings, but in between there will be some in colour. So there are far too many really to feature meaningfully in this column but I thought I could share a few particularly interesting ones for you. I'm at the moment working my butt off sorting through huge numbers of the myriads of prehistoric crocodiles, crocodile ancestors and relatives, and side branches of the croc family tree. The group was ridiculously diverse in the past.

Here for you today I show you just a few of the ones of whom nice fossils have been found right here in South Africa. My country has an amazingly rich fossil record. During those heady old days of Pangaea and later Gondwana, what today is South Africa was largely covered in water, a huge inland sea or large collections of swamps and lakes, and sediments were continuously washed into what today is called the Karoo Basin, and amidst the sediments were the bones and other remains of many critters that lived in the seas or along the shores. Later the inland region was uplifted and the waters drained away, and at times there might even have been a Sahara-sized desert in southern Gondwana. Today, most of the region is a high and dry region called the Karoo, covered in grass and low scrub. The ancient fossils are revealed as erosion is now cutting into the miles-thick layers of petrified sediments.

The fossil layers of the Karoo Basin start with the Dwyka Group, which was deposited in the late Carboniferous, about 330 million years ago, and into the early Permian. These contain few animal fossils, but many remnants of plants. At that time, South Africa was close to the south pole and was largely covered in glaciers; the forests were botanically not very diverse. In the Permian, the climate improved. The Ecca Group stretches from early to middle Permian, and contains fossils of marine fishes and some primitive swimming reptiles, but still little fossils of land life. The next group, the Beaufort, covers the middle Permian to the early Triassic. Now the climate seems to have become even more equable, and abundant fossils of land life include some of the world's best of the ancient therapsids, the precursors of the mammals (of which I've written a slew of articles for thus column). There is a bit of a gap from the middle Triassic to the start of the Jurassic, but the Stormberg Group then commences the geologic record again, showing us what some of the oldest African dinosaurs looked like. Finally the record practically ends in the early Jurassic, about 180 million years ago, with incredibly violent volcanic eruptions towards the eastern edge of the Karoo Basin. Much of this interior basin was then buried beneath about a mile of basalt; since this was deposited as lava, there weren't remains of animals in it. This volcanic basalt formed a cap on the earlier sedimentary layers, though. Later still, the interior was uplifted more and now became dominated by erosion rather than deposition. But this erosion uncovered the fossil bones from the critters of the primeval ages, for us inquisitive humans to find.

So what now of the critters I show you today? These were found in the Stormberg Group, the final ones before the great volcanoes, deposited in the early Jurassic. Now this was the time when dinosaurs started to dominate the world, but at least here in South Africa they shared their environment with many others that also flourished and diversified. One such group was the ancient ancestors of the crocodilians, and indeed that's what these three were!

Now you may already have heard that crocodiles are ancient beings that go back to the time of the dinosaurs. But what is usually not said is that actually ancient crocodilians were often not very similar to the living ones. When we go back to the early Jurassic, most of them were like the ones you see here: small and delicate, but already specialized for numerous different ways of life! Only later in the Jurassic did some of them start looking like present-day crocs and adopting the water-stalking life, and even then there were a great many other, very different kinds, from ones that lived fully marine lives, to fast-running hunters on land, to heavily-armoured vegetarians, and some that may even have been able to climb trees!

The ones you see here were not yet true crocodilians but ancestors of theirs, a group called 'Crocodylomorphs' or 'Crocodile Forms'. Sphenosuchus ('Wedge Crocodile') is known from excellent skull material but little of the rest of the skeleton; it was lightly-built and might have been able to run on its hind legs. Generally all crocodiles today, as was the case for extinct ones also, have hind legs longer than the front, and this may because very early crocodilian ancestors went through a bipedal phase. Indeed, Sphenosuchus gives us a very important clue as to what these ancestors would have been like, and very similar contemporaneous crocodoids were found in America. It reached a total length of about 1.4 m/4'7" including its tail, about the size of a fairly large dog. Its skull was about 20cm/8" long, with a high, narrow snout. It lived entirely on land, and hunted its prey by chasing it down. It held its body high on upright legs, rather than with limbs sprawling sideways.

The next one, Orthosuchus ('Straight Crocodile'), is known from a well-preserved fossil missing only some of the foot and leg bones, found in Lesotho, the country entirely enclosed inside South Africa. The fossil shows that it was small, only about 60 cm/2' in total length. Some of the broad, bony plates protecting its back were also preserved, and it likely had hard scutes over much of the rest of its body also. It appears to have been amphibious, with adaptations both to living on land and in the water. It had bony and soft palates separating its nostrils from most of its mouth opening, which would have helped it keep water out of its lungs even when submerged and clamping down on struggling prey. It also had earflaps covering its ear openings, again to keep water out. Its eyes and nostrils were close to the top of its head, so it could swim up to prey without revealing too much of itself. Its snout was short and narrow, with equal-sized teeth good for grabbing slippery fish prey. But it still had proportions of a land-walking animal, with longish legs held under its body, and may have hunted terrestrial prey also.

The last one, Litargosuchus ('Fast-running Crocodile') was a very small and slender type. It measured only about 50 cm/20" in total length, and with its very light build, likely weighed less than a kg/2 lbs. It, too, might have been able to run fast on its long hind limbs. It likely chased down small prey such as a variety of lizard-like critters, invertebrates including flying insects, and even the tiny, shrew-like first mammals such as Megazostrodon which lived at the same time in the same place. Like crocodiles, but even more so, these tiny early mammals would subsequently be going through a whole lot of interesting evolution.

Well there you have just a few of the very earliest crocodoids that happened to leave some nice fossils for us to stumble upon here in Southern Africa!

Willem

09.09.24 Front Page

Back Issue Page