Nearly fifty years ago, in 1965, Polish paleontologist Zofia Kielan-Jaworowska led a joint Polish-Mongolian expedition to the Gobi Desert. In the northwest of this desert, in southern Mongolia, is the Nemegt Basin, south of the mountains of the same name. This region is also known as the “valley of the dragons”, due to the large number of fossils and dinosaur footprints that have been found there.
At the beginning of July the group was working in the Altan Ula deposit III, unearthing a skeleton of a tarbosaurus, a large tyrannosaurid that lived in Asia 70 million years ago. July 9 dawned with rain, and since it was not possible to work with fossils, Kielan decided to explore and went to the southern area of the site, where he found, embedded in a sandstone rock, some extraordinary fossil bones, arms ending in claws thirty centimeters in length. Nothing like this had ever been seen; to the point that, when she returned to the camp and told her companions what she had found, no one wanted to believe her. But the bones were there, and the next day they began to dig them up. They were only able to unearth the arms, which were nearly eight feet long, the hands, each with three long fingers, the shoulders, and some fragments of ribs and vertebrae. There was nothing else. Tooth marks on the bones indicated that the animal had been eaten by a tarbosaur, probably when it was already dead, and some of the bones the tarbosaur had left behind had eroded over time. By its anatomy, the arms belonged to a bipedal dinosaur, and were the largest ever found.
The formal description of the dinosaur was published by two other Polish paleontologists on the expedition, Halszka Osmólska and Ewa Roniewicz, in 1970. The new species was given the name Deinocheirus mirificus, which means “peculiar terrible hand”, and a new species had to be created for it. new family, that of the deinoquirids, with certain characteristics in common with the ornithomimosaurs, a group of theropod dinosaurs, such as tyrannosaurs, velociraptors… and birds. But all previously known ornithomimosaurs were graceful, ostrich-like omnivorous running dinosaurs no more than four meters in length.
For decades, no more bones of this mysterious dinosaur were found, and paleontologists disagreed on what the animal’s body and head would look like. While some agreed with the discoverers, and considered it a giant ornithomimosaur, for others it was a huge carnivore that killed its prey with its huge claws, and others saw it as the dinosaur equivalent of a giant sloth.
Until, on August 16, 2009, a team of paleontologists from Korea, Mongolia, Canada, and Japan discovered at the Bugiin Tsav site, also in the Valley of Dragons, an almost complete skeleton of a huge dinosaur with one left arm. which was identical to that of Deinocheirus, although 6% larger. But the site had been plundered by looters before paleontologists found it, and two very important pieces were missing: the head and the feet. Studying the bones, the paleontologists realized that they already had another skeleton of the same dinosaur, discovered three years earlier at the site of Altan Uul IV, the mountain of gold, a few kilometers further south, near the site of the discovery of the first fossils. This skeleton, which was 25% smaller, was missing the front half, so it had no arms and could not be known at the time to be another Deinocheirus.
Meanwhile, a European collector whose name has not been made public had shown paleontologist François Escuillié, director of Eldonia, a French company dedicated to the fossil trade, a strange skull and dinosaur feet. In 2011, Escuillié showed the fossils to Pascal Godefroit, a paleontologist at the Royal Belgian Institute of Natural Sciences. Suspecting that they were the missing pieces of Deinocheirus, Escuillié and Godefroit contacted the discoverers of the 2006 and 2009 skeletons and verified that the skull fit perfectly in one of them. Ultimately, Escuillié bought the fossils and donated them to the Royal Belgian Institute, which in turn returned them to the Mongolian government in May 2014. Today, all the bones are in the Central Museum of Mongolian Dinosaurs in Ulaanbaatar.
Now, with the complete skeleton, paleontologists have been able to piece together what Deinocheirus looked and lived, and it’s even stranger than anyone could imagine. Deinocheirus was a huge bipedal dinosaur, thirty feet long, fifteen feet tall, and over six tons in weight, almost as big as a Tyrannosaurus. Although related to the light and fast ornithomimosaurs, Deinocheirus was a slow and heavy dinosaur. The head is more than a meter long, and its shape is reminiscent of that of a horse; the snout is long and flattened, similar to that of hadrosaurs or duck-billed dinosaurs. It’s actually more duck-like than the duck-billed dinosaurs themselves. It has no teeth, but a keratin beak. The jaw muscles are weak, so it doesn’t have a strong bite. The nostrils are located on the upper part of the snout, and the eyes are relatively small.
The dorsal vertebrae of Deinocheirus extend upward into long, flattened spines that support a sort of sail or hump and anchor the strong ligaments necessary to support the weight of the animal’s enormous abdomen and legs. For this same reason, the posture of Deinocheirus is not as horizontal as that of other ornithomimosaurs and most theropods, but more upright. The hind legs are relatively short, with short, broad toes ending in hooves.
The last two vertebrae at the end of the tail of Deinocheirus are fused together to form a structure called a pygostyle. In birds, the pygostyle supports the tail feathers, so it is very likely that Deinocheirus had a fan of tail feathers. And since other ornithomimosaurs are known to have been covered in feathers, surely Deinocheirus was too.
During the excavation of one of the Deinocheirus skeletons, more than 1,400 polished stones, as well as scales and fish vertebrae, were found in the stomach area. The stones are similar to those that ostriches and other birds swallow to crush their food, which are called gastroliths, and they compensate for the lack of teeth.
All these data tell us that Deinocheirus is a slow-moving, semi-aquatic omnivorous dinosaur. The feet, wide and ending in hooves, as we have said, facilitate movement and stability in the slippery muddy sediment at the bottom of rivers and lakes. Deinocheirus feeds on plants that it plucks up with its broad beak and swallows with the huge tongue that lodges in its deep lower jaw. The huge claws are a formidable defensive weapon, and they also serve to procure food. With them you can reach higher branches than with your beak, and you can also use them to fish. Although not, as we might imagine, catching their prey with them; those hands could not be closed to grasp things, like ours. What it does is remove the muddy bottom with them to cloud the water and scare away small animals, fish and invertebrates, that hide there, while sweeping the water with its beak. In the confusion, some of these animals climb into its wide beak and are swallowed. It is the same strategy, except for the use of claws, of course, which are used today by spoonbills, those long-beaked, spoon-shaped wading birds found in wetlands on all continents.
CONSTRUCTION OF GERMAN FERNÁNDEZ:
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