2018-06-21 11:32:52
Almost two hundred years ago, in the thirties of the century XIX, Sir Thomas Mitchell, director of the Survey of New South Wales, sent the famous English anatomist Richard Owen some bones found in a cave near Wellington, northwest of Sydney. Owen published the description of the new animal, which he named Diprotodon, in 1838. It was a huge quadrupedal marsupial, resembling a horned panda or rhinoceros, with characteristic lower incisors up to a foot in length, resembling those of from rodents, which are the ones that give it its name: Diprotodon means “first two teeth” in ancient Greek.
The following decade, German explorer Ludwig Leichhardt found large numbers of Diprotodon bones in streams in the Darling Downs region of Queensland. He also sent the bones to Owen, to whom he commented that they were so well preserved that he expected to find living diprotodonts in the then unexplored central regions of Australia. He unfortunately he did not succeed. Not with Diprotodon or anything; In 1848, on his second attempt to cross the Australian continent from east to west, his entire expedition mysteriously disappeared without a trace. Even today we don’t know for sure what happened to them.
Diprotodon is the largest marsupial we know of. The largest specimens reached the size of a large male hippopotamus: three meters in length, two meters in height at the withers and almost three tons in weight. Since its discovery, up to eight species of Diprotodon have been described, but today it is accepted that only one species exists, with marked sexual dimorphism: the size of the females is half that of the males.
The bone structure around the nostrils indicates that Diprotodon has a highly specialized snout; some paleontologists suggest that it has a small trunk, like a tapir, while others believe that its rhinal cavity, the hairless area around its nostrils, is huge and similar to that of its relative, the koala. The two upper incisors are spatula-shaped, while the lower two, projecting forward, are long and chisel-shaped, suitable for a diet of hard, thorny plants. The legs are short and thick, like columns. The feet and hands, which, as in the case of bears, rest on the ground when walking, are small, with little mobility in the joints; like their wombat relatives, they are turned inward. It has strong claws on its front legs, with four fingers, the same as on the hind legs. Interestingly, the longest finger is the outer one. Hair markings in its fossil tracks indicate that it is covered in wombat-like fur. The marsupium, the bag in which they raise their young, opens backwards, also like wombats.
Diprotodon is a browsing herbivore, which feeds on leaves, shoots, grasses and roots in the open forests, thickets and steppes where it lives, always near water. The males fight for the females and live alone; the females form groups for the rearing of the young.
Diprotodon’s incisors, like those of rodents, grow throughout life. Thanks to the study of the isotopes contained in the growth layers of one of these teeth, it has been possible to know that the diprotodonts undertook annual seasonal migrations, like zebras in Africa, in search of food. Strontium isotopes, related to local geology, vary twice a year, while carbon isotopes, related to diet, remain much more stable, suggesting that the type of food Diprotodon consumed did not vary throughout the year. of the year. Diprotodonts are the only marsupials for which we know of such migrations. On their way, about two hundred kilometers, they came across flooded plains, in which sometimes entire groups were trapped. When a seasonally briny lake dries up, a salt crust can hide the mud, which becomes a trap for large animals trying to cross. In Lake Callabonna, a dry lake in South Australia, hundreds of individuals have been found to die this way; the bodies were submerged, trapped in the mud and are well preserved, but the heads, exposed to predators and inclement weather, are broken and misshapen.
Diprotodon fossil bones, as well as hairs and footprints, have been found all over Australia; most of the finds correspond to groups that died because of the drought. In fact, the aridification that Australia has been suffering in the last million years was one of the possible causes of its extinction.
Diprotodon, which appeared 1.6 million years ago, went extinct about 40,000 years ago, shortly after humans arrived in Australia. It is possibly depicted in cave paintings in the Quinkan region, on the Cape York Peninsula, in the northeast of the country. It is probable that the human being also had to do with its extinction. Before the arrival of man, only the largest predators, such as the marsupial lion, dared to deal with diprotodonts, as attested by the bite marks on some fossils. But other fossils show incisions that betray their consumption by humans. In addition, the aborigines regularly burned scrub and forest areas to drive out game animals and to encourage the growth of the plants they fed on, thus altering ecosystems, replacing moist forests with more climate-tolerant vegetation. fire, like eucalyptus, and by meadows. And Diprotodon, the largest marsupial we know of, disappeared.
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