Arsinoitherium
Created | Updated Jun 16, 2019
Arsinoitherium
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!"
Back to the past we go yet again! I've devoted many articles now to the proto-mammals that lived mostly before the dinosaurs; the true mammals evolved from them, but during the reign of the dinosaurs did not diversify much. Well, they did indeed diversify, and there were digging, swimming, climbing and gliding types, but all were on the small side, especially compared to the big dinosaurs. But when the non-avian dinosaurs went extinct about 65 million years ago, mammals suddenly had no competition and many kinds inflated rapidly to become big plant and meat-eating types. Old Arsinoitherium zitteli was one of these – that is to say, on the plant-eating side.
Arsinoitherium means 'Arsinoe's beast'. Who was Arsinoe? Arsinoe I was the wife of Pharaoh Ptolemy II, who reigned in the third century B.C. The fossils of Arsinoitherium zitteli were found in Egypt, in the Fayum Oasis, where there used to be a religious centre named after queen Arsinoe. The species name, 'zitteli', honours the German palaeontologist Karl Alfred Ritter von Zittel, who delved into the prehistory of Egypt. A related species, Arsinoitherium giganteum, which as you might guess was a bit larger, was found in Ethiopia. Arsinoitherium is known from complete skeletons preserved in the Fayum oasis, along with numerous other fascinating mammals from the same period. The period in question is the late Eocene to the early Oligocene, from about 36 to 30 million years ago. It was a time still part of the early history of the diversification of the mammals; some were quite unlike any mammals living today, but the very earliest forms of modern types like elephants and monkeys were already recognizable, and bats were pretty much as fully evolved as they are today.
But Arsinoitherium was a kind of thing that has no counterpart today. It looks a bit like a rhinoceros, to which it is only very distantly related. It is more closely related to elephants, manatees and dugongs, and hyraxes! Two long and heavy 'horns' rose over its forehead, each with a small backwards-pointing prong at the base. These were bony, unlike the horns of modern rhinos that are made of keratin, the substance of hair and nails. But there might have been a sheath of keratin covering the bony horn cores of Arsinoitherium. Heavy-bodied and thick-limbed, it was not a fast animal. It reached about 2m at the shoulder, the size of a modern white rhinoceros. Unlike rhinoceroses, it had a jaw filled with an uninterrupted row of teeth from the front to the rear; in total its teeth numbered 44. The teeth were also not as high and robust as rhino teeth. It was likely a browser of leafy plants, incapable of dealing with very tough vegetation. Back then, North Africa was covered in tropical forest, in the swampy or marshy parts of which lived Arsinoitherium. Its size protected it against predators of the time and place, which were mostly of the more primitive kinds, such as hyaenodonts or oxyaenids. Modern predators like cats and dogs were only just starting to evolve, were still very small, and had not yet reached Africa at that time.
Animals related to Arsinoitherium were found in much of northern Africa, even as far south as Angola, and also in Asia and eastern Europe. The group was named the Embrithopoda. It flourished from the Palaeocene, the period directly after the extinction of the dinosaurs, to the Oligocene. Arsinoitherium was the largest and also the last known of the group; they went extinct leaving no descendants.
