Mamenchisaurus
Skeletal reconstruction of Mamenchisaurus hochuanensis in the Field Museum of Natural History in Chicago.
- People's Republic of China
Mamenchisaurus is a genus of sauropod dinosaur that lived during the Late Jurassic in China. Known to the public Mamenchisaurus particular was because of the extremely long neck, which accounted for half of the total length of the beast, and out up to 19 cervical vertebrae, more than in any other sauropod.
The first Fund, a partial skeleton without skull, was discovered in 1952 on a road construction site in Sichuan Province and described in 1954 by the famous Chinese paleontologist CC Yong as Mamenchisaurus constructus. Since then, numerous other findings were described - most studies currently distinguish six types.
- 4.1 Literature
- 4.2 Notes and references
Naming
The name Mamenchisaurus ( Mǎménxī马 门 溪, by马Mǎ (horse) ,门mén ( gate) and溪xī (stream, stream) ) is a misspelling of Mǎmíngxī (马鸣 溪), a river ferry on the River Jinsha Jiang (金沙江) near Yibin (宜宾) in Sichuan, which lies near the site where the first skeleton was discovered.
Features
Mamenchisaurus was a great representative of the sauropods. While known only by a single skeleton type species Mamenchisaurus constructus is estimated at 13 meters overall length, Mamenchisaurus hochuanensis was probably much greater; as the largest discovered specimen of this type measure approximately 22 meters in length. Weight estimates of this specimen vary depending on the study from 14.3 to 18.17 tons. Mamenchisaurus sinocanadorum and Mamenchisaurus jingyanensis may have become up to 26 meters long - these species are, however, survives only by very fragmentary skeletons.
A complete skull is known only from the type Mamenchisaurus youngi. This skull was extremely small in relation to body - including mandibular he measured 51.0 cm long, 19.8 cm wide and 40.1 cm high, with a neck length of almost 6 meters. The brain cavity of this skull showed a volume of only about 60 milliliters. Overall, the skull was similar to that of the Camarasaurus, but was thinner and longer. Good pronounced Skleralringe around the eyes refer to a good sense of sight. The mandible was relatively low at the front ( pubic symphysis ) and showed a small lateral opening ( external Mandibularfenster ) - this opening was closed with all other sauropods except Shunosaurus. The chisel-like teeth were close to each other. In the upper jaw were on each side 14 to 18 teeth in the front of the upper jaw premaxilla contained four teeth present. The lower jaw on each side, meanwhile, contained 18 to 24 teeth.
The spinal column was made up of 18-19 cervical vertebrae, 12 dorsal vertebrae, 4-5 sacral vertebrae as well as more than 50 caudal vertebrae together. The neck was one of the relatively longest of all sauropods and was more than three times as long as the hull, the largest known specimen of Mamenchisaurus hochuanensis extent of the neck over 9.8 meters in length. Only the remains of the related genus Omeisaurus suggest an even longer compared to the total length neck. The cervical vertebrae were characterized by very long cervical ribs that ran along the cervical spine down and Mamenchisaurus sinocanadorum a length of up to 4.1 meters reached. Whether Mamenchisaurus his neck only held horizontally or was able to straighten it like giraffes to graze at high altitudes can, is controversial. A recent biomechanical study notes, however, that the neck was immobile due to the very long neck ribs to lift him - unlike representatives of Diplodocidae whose neck was significantly more flexible and potentially allow an erection. In other features, the spine of the Diplodocidae possible: Thus, the spinous processes of the posterior cervical and anterior dorsal vertebrae were forked; also helped the middle caudal vertebrae typical double- beam -like chevron bones.
Located in front of the sacral vertebrae were opisthocoel, that is on the front convex and concave at the rear. In contrast, the proximal caudal vertebrae showed the reverse constellation ( procoel - at the front of concave and convex at the rear ), while the middle caudal vertebrae amphiplat ( on the front and rear flat) were. Further information relevant to the delimitation of the genus characteristics are also found in the shoulder girdle and extremities: So the shovel-like lower end of the scapula was increased, the entire bone was longer than the femur. The sternum was small and nearly round. The length ratio between the front and hind leg was about 3/4 to 4 /5, both front and hind feet were also small in comparison.
Shunosaurus
Mamenchisaurus
Omeisaurus
System
Outer systematics
The systematic classification of Mamenchisaurus is controversial. John McIntosh (1990 ) considered the genus for a representative of Diplodocidae, based on the double beam -like chevron bones, the forked spinous processes and the procoelous caudal vertebrae. Later, however, it turned out that these features can be found not only in representatives of Diplodocidae, but also in many other Sauropodengruppen. Paul Upchurch (1995, 1998, 1999 ) ranked Mamenchisaurus contrast to the Euhelopodidae - this grouping is now regarded as paraphyletic since Euhelopus is only distantly related to Mamenchisaurus.
Today Mamenchisaurus is considered an original representative of Eusauropoda, however, the important features of the more advanced sauropods ( Neosauropoda ) were missing and thus is outside the Neosauropoda. Frequently Mamenchisaurus is classified along with probably closely allied forms within a Mamenchisauridae said group. What genres are allocated next to Mamenchisaurus this group, however, is controversial - but frequently the genera Chuanjiesaurus, Eomamenchisaurus, Tienshanosaurus, Tonganosaurus, Omeisaurus and Yuanmousaurus be placed in this group.
Inside systematics
Paul Upchurch (2004) noted that the internal systematics of Mamenchisaurus was very confusing and requires the kind of revision. So many described as Mamenchisaurus findings were not sure assigned to this genus (trash - taxon ).
Currently six species are recognized; some studies lead to a possible seventh type - Mamenchisaurus fuxiensis - whose status is unclear.
- Mamenchisaurus constructus Young, 1954: The type species is based on a single incomplete skeleton, the skull, shoulder girdle and front legs are missing and that was part of an approximately 13 -meter-long specimen. The skeleton comes from the Shangshaximiao formation of Yibin in Sichuan.
- Mamenchisaurus hochuanensis Young & Zhao, 1972: This species is so far at least five skeletons known of these specimens includes remains of the cranium. A full of traditional neck consists of 19 cervical vertebrae. The largest specimen is estimated to have a length of 22 meters. The skeletons are from the Shangshaximiao formation of Zigong in Sichuan and Hechuan and from the Hengtang formation of Yeongdeungpo in Gansu.
- Mamenchisaurus sinocanadorum Russell & Zheng, 1994: A very large species that is known only by a cervical spine series with an incomplete skull, which comes from the Shishugou formation of Jungger in Xinjiang.
- Mamenchisaurus youngi Pi, Ouyang & Ye, 1996: Of this kind one, but nearly complete skeleton with complete skull is known. This specimen is estimated to have a length of 16 meters. It comes from the Shangshaximiao formation of Zigong in Sichuan.
- Memenchisaurus anyuensis He et al, 1996:. Known are a relatively complete and four incomplete skeletons, which are estimated to lengths of about 21 to 23 meters. These findings are from the Penglaizheng formation of Anyue in Sichuan.
- Mamenchisaurus jingyanensis Zhang, Li & Zeng, 1998: This species is known by three incomplete skeletons - one of these skeletons has an incomplete skull. The length of these specimens is estimated to be 20 to 26 meters. The findings come from the Shangshaximiao formation of Jingyan in Sichuan.
- Mamenchisaurus fuxiensis ( Hou, Zhao, & Chao, 1976): This problematic species was originally described as a distinct genus - Zigongosaurus. There might, however, a kind of Omeisaurus or Mamenchisaurus. The only fund consists of several disjointed bones that come from the Shangshaximiao formation of Zigong in Sichuan.