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!"

Here I have another prehistoric critter for you all. This is a very special one - Deinocheirus mirificus - one of the strangest of all dinosaurs. It is one very near and dear to me! I've been interested in dinosaurs since I was six or so years old, and my father helped me out very much by getting books on them for me, from the university library where he worked, as well as from various excellent book shops in Pretoria, which he also knew well and which we visited frequently.

One kind of dinosaur discussed in the books was the enigmatic Deinocheirus – the name is Greek for 'Terrible Hand'. Indeed, this dinosaur was then (at the time I read them, the nineteen seventies) known only from a single fossil specimen, which consisted of no more than a pair of arms (and shoulder blades) of immense size, found in the Gobi Desert of Mongolia by a team led by the Polish scientist Zofia Kielan-Jaworowska. The arms alone measured about 2.4 m (8') each! They ended in enormous curved claws. Nothing was known of the rest of the body of this animal. It wasn't even clear what kind of dinosaur it was! Was it a predatory dinosaur related to, maybe, Tyrannosaurus rex? But that one had proportionally tiny arms. Was Deinocheirus even bigger than Tyrannosaurus, and what did it use its frightful arms for? Some palaeontologists speculated that it could use its powerful arms and claws to disembowel giant sauropods with a single swipe.

By the nineteen eighties, more was deduced about where this dinosaur fit in and how it might have lived. Careful comparison of the shape and build of its arms and shoulder blades suggested its nearest relatives to be the so-called Ostrich Dinosaurs, or Ornithomimosaurs. But those were lightly-built runners, not much larger than the ostriches to which they were compared. If Deinocheirus was an ostrich dinosaur and proportioned like the others, it must have been ridiculously big – but then, wouldn't it be much too heavy to be a fast runner? In a different vein, analysis of its arms showed that the claws were rather blunt, and not very good as offensive weapons, but they could have been used for defense against other (huge) predators. Another scientist speculated that they might have been used for climbing, grasping tree limbs like a sloth – but again, their size meant that Deinocheirus would have been the largest tree climber ever, and no other dinosaur (at the time) was known to climb trees.

But all of this talk, in the absence of additional fossil remains, were up in the air. For long, I wondered if the mystery would ever be solved. What if there simply were no other fossils of Deinocheirus preserved? The act of a dead animal being actually preserved in such a way as to last for millions of years, happens extremely rarely, and we can assume that perhaps most species that have lived on this planet, have passed without leaving a trace. And some that have been fortunate enough to leave traces, might have left only a handful of them. Many extinct species are known from very spare remains, sometimes a single bone. If Deinocheirus was one of these, we'd simply be out of luck.

So my puzzlement over old Deinocheirus lasted for a couple of decades more – and then everything changed. In 2013, it was announced that new fossil material of it had been uncovered! I was ecstatic. The fossils included two individuals and bones of essentially the entire body and skulls too. And they revealed what we never would have guessed about Deinocheirus just from its arms!

It was indeed an ostrich dinosaur – which is to say, related to the others in the group, classified along with them, but also unlike any of them. It was indeed huge – at 11 m overall at adulthood, almost twice as long as the next biggest ostrich dinosaur – and very bulky. Even so, most of its bones were hollow to make them lighter, and to aid its respiration – like birds, it had extensive air-sacs throughout its body, that were linked with its lungs. It likely reached about 6.5 tons in weight, comparable to an adult bull African elephant, but it would have looked even larger. It had a skull unlike the other ostrich dinosaurs, with a long 'bill' with a wide, flat tip. Its eyes were comparatively small, and its lower jaw was much deeper than the upper. Strangest of all, it had very long spines sticking up from its backbones, forming a tall 'sail' or maybe a hump over its back. It was indeed not a fast runner, though it walked on its hind limbs. Its legs were thick and stout, and its feet ended in broad, almost hoof-like claws. Its arms were actually not that large compared to the rest of its body. Its tail ended in a structure of fused vertebrae similar to the pygostyle of birds, the left-over bones of the tail that support the tail feathers. Since we now know that ostrich dinosaurs had feathers, it is likely that it, too, had feathers, likely including vaned feathers on its arms and the end of its tail.

So we now have the picture of a very odd dino indeed. But how did it live? What did it use the arms for? Its toothless skull shows that it wasn't a predator, at least not of large prey, and it wouldn't have had a strong bite. Its broad-tipped bill would have suited for nipping off soft plants. Its deep lower jaw would likely have housed a voluminous tongue, which it might have moved forward and backward to create suction to pull in water plants, or fishes. Indeed, there were fish remains in the belly cavity of one specimen. There were also lots of stones called gastroliths in the belly cavity. These are associated with herbivory, being used to grind down plant food in the stomach.

All of this fit in with the environment in which Deinocheirus lived ï– what is today the Nemegt Formation in the Gobi Desert was at the time, the Late Cretaceous, about 70 million years ago, an expansive swampland with meandering streams amidst trees and lush vegetation. Deinocheirus would have plodded through the swamps, using its long arms to pull up aquatic vegetation, or dabbling with its duck-like bill in the water to suck in smaller floating water plants or fishes. It could also use its arms to pull tree branches close to nip off high-growing foliage. Its claws would have defended it, though not always successfully, against the giant predator Tarbosaurus, an Asian relative of Tyrannosaurus, bite marks of which have been found on some of its fossilized bones. Its sail-like back could have been a display feature, but it might also have been functional, with tendons running from the tall spines down the back to stiffen the spine and stabilize the torso, enabling it to keep its body upright as it walked.

So, we finally know what old Deinocheirus was – sort of! A very large and aberrant ostrich dinosaur, living the lakeside life and feeding on fishes and soft vegetation. I find it amazing that we even got those complete fossils – and we now also know a lot of the rest of the ecology of those ancient swamplands. Many other dinosaurs occurred in them, including long-necked sauropords, armoured dinosaurs, thick-headed dinosaurs, hadrosaurs, various two-legged carnivores, and a few ancient birds. Deinocheirus definitely is the strangest one of them all, and its bizarre shape just shows what can come about through evolution, and the fortuitous way in which we came across its remains, hints at the possibility of us finding a few more similarly strange and wayward evolutionary offshoots.

Willem

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