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!"
I hope you folks don't mind another prehistoric special! These will feature here from time to time since I want to share with you the pictures and info from the compact guide to prehistoric life that I'm working on. They'll be a bit out of order here … in the guide itself, everything will be arranged according to time, place, and relationships. But in real time, I'm drawing them according to what I'm most inspired by on any particular day. For this entry, let's look at some Pantodonts!
Back with the Big
My previous prehistory special treated the therocephalians, a diverse group of pre-mammals that existed before the dinosaurs came on the scene. Today's article deals with the pantodonts, which is a group of true mammals that lived just after the (non-avian) dinosaurs departed the scene! As such, they were the first group of mammals that reached truly big physical proportions. In all the time the dinosaurs reigned – about 140 million years – the mammals remained quite small, mouse-sized to cat-sized or at most badger-sized. They couldn't move into the ecological niches of large herbivores or carnivores, since the dinosaurs very successfully occupied those. Many mammals were likely nocturnal, creeping around in the dark when the dinosaurs were sleeping, surviving by being inconspicuous and unobtrusive.
That changed suddenly and dramatically about 65 million years ago. A catastrophe – an asteroid or comet strike or something similarly calamitous – caused the almost instantaneous extinction of all the large dinosaurs. Only birds, descended from small dinosaurs, remained. This post-extinction period is called the Palaeocene. The global ecology reeled; there must have been major instability and waves of extinctions as food-webs collapsed. Into this chaotic landscape stepped the mammals, those hardly noticeable yet notably hardy little critters, who survived the extinction event and now flourished. Mouse or rat sized at first, they diversified rapidly, making use of the suddenly vast food reserves and empty landscapes that were open to them.
One of the first and most successful groups of these mammals were the Pantodonts. In my series of illustrations you can see how they changed over a relatively short period of time (geologically speaking, that is – for us, being a few millions of years, quite an unimaginably long time). Please realize that my reconstructions of them are largely imaginative, since we don't really know exactly what they looked like in the flesh and fur. The proportions are according to the known bones but the colours and coat patterns are entirely my own invention.
Our first pantodont is named Alcidedorbignya inopinata. The name is a mouthful, but it was named for famed French naturalist of the nineteenth Century, Alcide d'Orbigny. This old critter was squirrel-sized, and lived right after the extinction of the dinosaurs, from about 65.5 to about 61.5 million years ago, in what is today South America (fossils found in Bolivia). Despite being so ancient, it is one of the best-known of all prehistoric mammals, known from complete and excellently preserved remains. It was about the size of a squirrel. It had a very generalist kind of build, able to dig, run and climb. It was likely omnivorous, eating insects and other small animals as well as fruit and some other plant material. This pantodont being the most primitive, poses some intriguing questions. It is the only one known from South America, the others having lived in North America, Europe and Asia. So did pantodonts originate in South America and then move northwards to colonize other lands while dying out in their birthland? Or did Alcidedorbignya originate in North America and then move south, its fossils simply not having been discovered in North America yet? We'll have to wait for further finds to be able to answer this.
The next one is Bemalambda pachyosteus, which more properly lived in Asia, from 65.5 to 58.7 million years ago. Once again we know it from wonderfully preserved remains. This pantodont was as large as a mid-sized dog, but had a comparatively small skull, while its limb bones were surprisingly thick and heavy. It, too, was likely an omnivore, and its powerful limbs might have been good at digging. It might have lived in burrows, or might have dug for roots, bulbs and tubers to eat.
From Bemalambda we move to Pantolambda bathmodon. This one lived in North America and Asia, and is one of the most familiar pantodonts. It was the size of a sheep; its skull was still small, and its body long and low, with a long tail. It flourished between 63 and 57 million years ago. While it still had long, sharp canine teeth, it had become more adapted to eating plants. It was no longer able to climb, or to dig very well, having lived by browsing soft herbs and shrubs. It might on occasion have eaten animal food such as carrion.
Our next pantodont looks fearsome. This is Titanoides primaevus. Lion-sized, it had a very much larger head than that of Pantolamba. It also had huge, sharp canine teeth. It was bear-like in its proportions, with long claws on its paws. It appears to have lived in tropical swampland (but bear in mind that the time was a very warm one, with tropical climes extending much further north and south than today). Despite its ferocious looks, it was likely mostly herbivorous, its teeth being for defense. It is known from North America, having lived 59-56 million years ago.
Bigger still was Barylambda faberi. Reaching a weight of about 650 kg, it was very heavily built with not only a big, barrel-like body but also very stout limbs, and a very thick, rather reptilian tail. It was not a direct descendant of Titanoides, but probably closer to Pantolamba. It is well-known from North America, 60-50 million years ago. Its skull was very small for its size. Only the males had lengthened canine teeth, and not nearly as large as those of Titanoides. Its size made it pretty much immune to predation. It also lived by browsing lush, soft plants. Its very thick and strong tail might have served as a prop so it could reach up on its sturdy hind limbs to reach high leaves and fruits.
Last, and largest, is Coryphodon eocaenus. This one was rhino-sized, reaching 700 kg in bodyweight. It also much resembled a (hornless) rhino or hippopotamus in shape. It had a long skull with sharp, curved, protruding canine teeth. It had a tiny brain for its size, yet it was very successful in its time. It lived not only in the late Palaeocene, but also survived into the next period, the Eocene. It also gave rise to descendants that lived into the mid-Eocene, the last-surviving pantodonts. Coryphodon itself was likely a dweller in warm, lush swamp country. Amazingly, this kind of almost tropical environment was to be found in the Eocene on Ellesmere Island, even then situated within the Arctic Circle.
While the climate was much warmer, those polar regions back then still had a very seasonal climate; most notably, the winters were very dark with the sun only rising low above the horizon and in some places and times not rising at all for many days. Coryphodon coped with this by modifying its diet. During the long, sunny days of summer it fed on lushly growing leafy plants; then as the colder, darker days set in, it changed over to eating twigs, leaf litter, evergreen coniferous plants, and fungi.
Coryphodon is known from North America, Europe and Asia, living from 57 to 46 million years ago. Its descendant, Hypercoryphodon, persisted a few million years longer in Asia, but then died out, and with it the entire line of the pantodonts came to an end. Many new lines of mammals took their place, including the earliest members of most present-day large mammal groups such as the elephants, rhinos, horses, hippos and other hoofed mammals. (There were also a few other, now-extinct, intermediate groups like the Dinoceratans and the Titanotheres, which I'll also treat here soon.) While in the Palaeocene there were hardly any large predators, these too began to evolve and in the Eocene started reaching a substantial size. Pressure from predators so prompted the large herbivorous animals to develop new, better defenses. Instead of the large canine teeth the early browsers used to defend themselves, the new herbivores developed an amazing diversity of types of horns on their heads and/or snouts, while also much improving their speed and running proficiency. Nevertheless, we still have some fairly unspecialized and quite primitive-looking types, like the tapirs, which still flourish in warm and lush regions. But they are not at all closely related to the pantodonts. Those early experimenters left us with no descendants or close relatives. They're gone forever, and yet, they were the first, the pioneers, preparing the way for the many big and spectacular mammals that were to follow.