Erketu
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Eddy of Erketu |
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| Temporal occurrence | ||||||||||
| late Lower Cretaceous | ||||||||||
| 112.9 to 100.5 million years | ||||||||||
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| Scientific name | ||||||||||
| Erketu | ||||||||||
| Ksepka & Norell , 2006 | ||||||||||
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Erketu is a genus of sauropod dinosaur belonging to the Titanosauriformes group thatlived inwhat is now Mongolia during the late Lower Cretaceous .
This genus is characterized by an extremely long neck, even for sauropods. Erketu was a medium-sized sauropod, but since only a fragmentary skeleton is known so far, no exact size can be given. Erketu was scientifically described with the only known species ( type species ) Erketu ellisoni in 2006 by Daniel Ksepka and Mark Norell .
The genus name Erketu alludes to Erketü Tengri, a god of Tengrism , while the epithet ellisoni honors Mick Ellison for his contributions to dinosaur research at the American Museum of Natural History.
Find and find location
The only find of this animal so far was made in 2002 by an expedition of the American Museum of Natural History and the Mongolian Academy of Sciences in Dorno-Gobi-Aimag , an aimag (administrative unit) in southeastern Mongolia. The expedition found a few vertebrae on the surface, the ground immediately in front of it contained the anterior neck section in an anatomical composite (articulated). - Next, the lower portion of the right leg could shin (tibia), fibula (fibula) and talus be salvaged articulated - (Astragalus). In addition, a heel bone ( calcaneus ) and the right breastbone (sternum) were found. However, the comprehensive search for the skull was unsuccessful, although the atlas , the first cervical vertebra, has been completely preserved. Finding a sauropod skull is generally very rare, as the skull was only weakly connected to the neck and, as it was only small in size, often did not stay with the rest of the body.
When the research team subsequently visited the site again, they discovered three more cervical vertebrae in the anatomical network that belonged to the same specimen. These vortices were described by Ksepka and Norell in 2010.
The Bor Guvé site, newly discovered by the 2002 expedition, was probably a floodplain at the time of the deposits. The remains of sauropods and turtles, as well as theropods - there is a large carnivore the size of an allosaurus and a member of the Maniraptora that was slightly larger than Deinonychus are known to have been found in this location . Fossil fruits were also discovered. The age of the layer is estimated to be in the late Lower Cretaceous - a more precise time cannot be given, however, as there is no suitable material for radiometric dating .
Sauropod fossils from Mongolia are rare and mostly very fragmentary. The discovery of Erketu - together with the discovery of Opisthocoelicaudia , a skull of Nemegtosaurus and Quaesitosaurus - is the only exception.
description
Compared to other sauropods, Erketu was overall long, but not very heavy. Whether the neck, which is very long due to the greatly elongated cervical vertebrae, was longer in relation to body size than that of other extremely long-necked genera such as Mamenchisaurus , however, cannot be said, since the total number of vertebrae is not known.
The cervical vertebrae are higher than they are wide and, in order to save weight, clearly opisthocoel, ie the vertebral centers are straight on the front and concave on the back. Another large depression is located on each side of the centers. A CT scan of the vertebrae shows that large parts of the center were filled with possibly air-filled chambers, with little more than a vertebral framework remaining. From the fourth cervical vertebra, upward, forked vertebral processes were found.
However, the most striking feature of the cervical vertebrae is their strong elongation. The so-called elongation index (egg, after Wedel et al. , 2000), the quotient of the length of the vertebral base and the height of the condyle , which is used to compare the length of the vertebrae with other sauropods, is greater in Erketu than in any other Sauropods, of which the corresponding material is known. A direct comparison with the very long-necked sauropods Omeisaurus and Sauroposeidon , which also have very long cervical vertebrae, is difficult, however, as good material is missing.
Significantly elongated cervical vertebrae or an increased number of cervical vertebrae to lengthen the neck are found in many sauropods. For example, Brachiosaurus only had 13 cervical vertebrae, but they were significantly elongated, while Euhelopus had 17 cervical vertebrae, but they were not elongated.
Systematics
Erketu is classified by Ksepka and Norell (2006) within the Somphospondyli (Wilson and Sereno, 1998), but outside of the Titanosauria , as some characteristics specific to the Titanosauria are missing. It forms a sister taxon to Euhelopus and the Titanosauria. In a more recent cladistic analysis, Ksepka and Norell (2010) see Erketu as a sister genus of Qiaowanlong , a sauropod recently described from China. Both genera show forked spinous processes of the cervical vertebrae, a feature that is not found in other genera. According to this analysis, Qiaowanlong and Erketu were more closely related to the Titanosauria than Euhelopus .
The possible family relationships are shown in the following cladogram (simplified from Ksepka and Norell, 2010):
| Titanosauriformes |
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literature
Unless otherwise stated, all information comes from the following work:
- Daniel T. Ksepka, Mark A. Norell : Erketu ellisoni, a Long-Necked Sauropod from Bor Guvé (Dornogov Aimag, Mongolia) (= American Museum Novitates. No. 3508, ISSN 0003-0082 ). American Museum of Natural History, New York NY 2006, (PDF; 2.02 MB) .
Individual evidence
- ↑ a b c d e Daniel T. Ksepka, Mark A. Norell: The Illusory Evidence for Asian Brachiosauridae: New Material of Erketu ellisoni and a Phylogenetic Reappraisal of Basal Titanosauriformes (= American Museum Novitates. No. 3700). American Museum of Natural History, New York NY 2010, (PDF; 448.89 kB) .
Web links
- Newly Discovered Dinosaur Had Giant Neck, Air-Filled Bones - National Geographic News with picture