Eomamenchisaurus
| Eomamenchisaurus | ||||||||||
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| Temporal occurrence | ||||||||||
| Middle Jurassic | ||||||||||
| 174.1 to 163.5 million years | ||||||||||
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| Scientific name | ||||||||||
| Eomamenchisaurus | ||||||||||
| Lu et al. , 2008 | ||||||||||
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Eomamenchisaurus is a genus of sauropod dinosaur from Central Jurassic China . So far, only a single, very fragmentary skeleton is known, which consists of parts of the spinal column, sacrum, pelvis and hind limbs. This genus was first scientifically described in 2008 with the only species Eomamenchisaurus yuanmouensis by Chinese researchers around Lü Junchang . These researchers placed Eomamenchisaurus among the Mamenchisauridae , a group of sauropods that has so far only been identified from China and which was characterized in particular by a very long neck. Eomamenchisaurus comes from the Middle Jurassic and is therefore geologically older than most of the other representatives of the Mamenchisauridae - the generic name also points to this fact ( Greek eos - "early"; Ch. Mǎménxī 马 门 溪; Greek sauros - "lizard"). The second part of the species name, yuanmouensis , refers to the Yuanmou districtin the Chinese province of Yunnan , where the fossils were discovered.
Location
The only previous find comes from Jiangyi in Yuanmou County in Yunnan Province; it was recovered from the same quarry from which the remains of the genus Yuanmousaurus were previously recovered. Today the fossils are in the local Lufeng Dinosaur Museum .
Systematics and characteristics
In their first description, Lü Junchang and colleagues put Eomamenchisaurus among the Mamenchisauridae. This group belongs to the Eusauropoda , to which all sauropods belong except for a few very original forms, but is classified outside of the Neosauropoda , to which all more advanced sauropods belong. The validity of the Mamenchisauridae is controversial, so it could actually be a paraphyletic collection of not closely related Eusauropods. According to Lu and colleagues, who consider the Mamenchisauridae as a monophyletic group, Eomamenchisaurus is an original representative of this group; however, a more detailed examination of the relationships (a phylogenetic analysis) is still pending.
The assignment to the Mamenchisauridae was based on various features of the sacrum, which, like other Mamenchisaurids, consisted of four sacral vertebrae: For example, the vertebral bodies made up more than a third of the total height of the vertebrae, and the first and second vertebral bodies of the sacrum were not connected merged. As with Mamenchisaurus hochuanensis , Mamenchisaurus youngi and Chuanjiesaurus , the ninth and tenth vertebrae were fused together.
Eomamenchisaurus can be distinguished from other genera by a number of features: For example, the vertebral bodies of the dorsal vertebrae showed no pleurocoele (lateral openings), while their front ends were flat to slightly convex . The length ratio between the tibia and femur was 0.64. The ischium showed a long, rod-like straight shaft, which was longer than that of the pubic bone .
Individual evidence
- ↑ a b c d e Lü Junchang, Li Tianguang, Zhong Shimin, Ji Qiang, Li Shaoxue: A New Mamenchisaurid Dinosaur from the Middle Jurassic of Yuanmou, Yunnan Province, China. In: Acta Geologica Sinica. English edition. Vol. 82, No. 1, 2008, ISSN 1000-9515 , pp. 17-26, doi : 10.1111 / j.1755-6724.2008.tb00320.x .