Erketu (lat.: Erketu) is a genus of sauropods from the Titanosauroforms group (Titanosauriformes), which lived on the territory of modern Mongolia at the end of the Lower Cretaceous. This genus of dinosaurs was characterized by an extremely long neck, even for sauropods.
Erketu was a medium-sized representative of the infraorder Sauropods (lat.: Sauropoda), however, since only one fragmentary skeleton of this animal is still known to science, it is impossible to indicate the exact size of its body.
The only (type) species of this genus, Erketu ellisoni, was scientifically described in 2006 by American paleontologists Daniel Ksepka.: Daniel Ksepka) and Mark Norell (Mark Norell).
The dinosaur owes its Latin generic name Erketu to the pre-Islamic and pre-Buddhist Turkic-Mongolian god Erketu Tengri, and the specific epithet ellisoni was given to him in honor of Mick Ellison (eng.: Mick Ellison, author of several reports on paleontological research at the American Museum of Natural History.
Place of discovery
The only erketu skeletal remains were discovered in 2002 by members of a joint expedition of the American Museum of Natural History and the Mongolian Academy of Sciences. During this expedition, carried out in Aimak Dornov in the southeast of the Mongol People’s Republic, several vertebrae were found on the surface of the Earth, and under a layer of soil right in front of them-the vertebrae of the front of the cervical spine, which were in anatomically related state.
Later it was possible to extract, also in a related state, the lower part of the right lower limb of the dinosaur a large berets, as well as a small berets and ram bones. In addition, the heel and the right side of the chest bone were found. However, the widespread search for the skull of the dinosaur was unsuccessful, although the first cervical vertebra, Atlant, was completely preserved. On the other hand, the find of the skull of Zauropod is usually a rarity, since it was weakly connected with the neck and because of its small size it was not often preserved with the rest of the body.
When later the same group of researchers revisited the site of the find, they found 3 more cervical vertebrae, which were also anatomically related and belonged to the same animal. These vertebrae were described by Ksepka and Norell in 2010.
In the era of the formation of sedimentary rocks, the area of Bor Gouve, where the bones of the erketu were found during the 2002 expedition, was presumably the area of flooding. Other finds from the same area include fossils of other sauropods and ancient turtles, as well as one theropod, a large carnivorous dinosaur the size of an allosaurus (lat.: Allosaurus) and one member of the Maniraptora clade, which was slightly larger than Deinonychus (Deinonychus).
In addition, fossilized fruits of plants were also found there. According to experts, this geological layer belongs to the end of the Lower Cretaceous, but it is impossible to determine its age more accurately due to the lack of suitable material for radiometric dating.
In Mongolia, sauropod skeletal remains are rarely found, and most often they are very fragmentary. The skeleton of an erketu, a skeleton of opisthocelicaudia (lat.: Opisthocoelicaudia), as well as the skull of a Nemegtosaurus (lat.: Nemegtosaurus) and the skull of a Quesitosaurus (Quaesitosaurus) are the only exceptions.
Description
Unlike other sauropods, the Erketu body was quite long, but did not have a very large mass. However, since it is not known how many vertebrae this dinosaur had in total, it cannot be said whether its very long (due to highly elongated cervical vertebrae) neck was longer relative to overall body length than other extremely long-necked sauropods such as Mamenchisaurus (lat.: Mamenchisaurus).
The height of the cervical vertebrae of an erketu exceeds their width, while they are strongly opisthocoelous, that is, they have a strongly pronounced articular tubercle in front and an articular fossa in the back, which ensured a decrease in the mass of his body. In addition, the cervical vertebrae are also deepened laterally.
Computed tomography shows that large parts of the centers of the vertebrae may have consisted of air-filled chambers. At the same time, on the cervical vertebrae, starting from the fourth, there were processes directed upwards and diverging in the form of a fork.
However, the most unusual feature of these vertebrae is that they are greatly elongated. Erketu has the so-called Wedel elongation index of the vertebrae (Eng.: elongation index sensu Wedel), which is the ratio of the length of the vertebral body in its center to the height of the condyle and used to compare the length of the vertebrae in different sauropods, is higher than that of any other member of this infraorder known to science.
However, to directly compare this dinosaur with other very long-necked sauropods, omeisaurus (lat.: Omeisaurus) and Sauroposeidon (Sauroposeidon), which, judging by the available fossils, also had very long neck vertebrae, is difficult due to the lack of well-preserved bone material.
Elongation of the neck due to significantly elongated cervical vertebrae or their increased number is found in many sauropods. For example, the brachiosaurus.: Brachiosaurus) had only 13 cervical vertebrae, however, they were significantly elongated, while Euhelopus (Euhelopus) had 17 of them, but they were not elongated.
Classification
In 2006, Daniel Ksepka and Mark Norell assigned the erket to the Somphospondyla hoard (lat.: Somphospondyli), but did not include it in the Titanosaurs (Titanosauria) group, as it lacks some of their characteristic features. According to this classification, the genus Erketu forms a taxon sister to Euchelops and titanosaurs.
However, in their later 2010 cladistic analysis, the same Ksepka and Norell classified Erketu as a genus sister to Qiaowanlong (lat.: Qiaowanlong), a recently described sauropod whose bones have been found in China.
The fact is that both of these genera have spiny processes of the cervical vertebrae diverging in the form of a fork, which are their unique feature. According to the results of the analysis, the qiaowanlong and erketu were more closely related to titanosaurs than to euchelops.
