Mamenchisaurus

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Mamenchisaurus
Skeletal reconstruction of Mamenchisaurus hochuanensis in the Field Museum of Natural History in Chicago.

Skeletal reconstruction of Mamenchisaurus hochuanensis in the Field Museum of Natural History in Chicago .

Temporal occurrence
Upper Jurassic ( Oxfordian to Tithonian )
163.5 to 145 million years
Locations
Systematics
Dinosaur (dinosauria)
Lizard dinosaur (Saurischia)
Sauropodomorpha
Sauropods (Sauropoda)
Eusauropoda
Mamenchisaurus
Scientific name
Mamenchisaurus
Young , 1954
Artistic live representation of Mamenchisaurus youngi
Skeleton reconstruction of Mamenchisaurus youngi in the Zigong Museum

Mamenchisaurus is a genus of sauropod dinosaur thatlivedin China during the Upper Jurassic . Mamenchisaurus is known to the publicin particular because of its extremely long neck, which made up half the total length of the animal and consisted of up to 19 cervical vertebrae, more than any other sauropod.

The first find, a partial skeleton without a skull, was discovered in 1952 on a road construction site in the province of Sichuan and described in 1954 by the famous Chinese paleontologist CC Yong as the Mamenchisaurus constructus . Since then, numerous other finds have been described - most studies currently distinguish a total of six species.

Naming

The name Mamenchisaurus (Mǎménxī 马 门 溪, from 马 Mǎ (horse), 门 mén (gate) and 溪 xī (stream, stream)) is a wrong spelling of Mǎmíngxī (马鸣 溪), a river ferry on the Jinsha Jiang River (金沙江) near Yibin (宜宾) in Sichuan, which is near the construction site where the first skeleton was discovered.

features

Mamenchisaurus was a great representative of the sauropods. While the type species Mamenchisaurus constructus, known only from a single skeleton , is estimated to have a total length of 13 meters, Mamenchisaurus hochuanensis was probably significantly larger; the largest specimen of this species discovered was an estimated 22 meters long. Weight estimates of this specimen vary between 14.3 and 18.17 tons, depending on the study. Mamenchisaurus sinocanadorum and Mamenchisaurus jingyanensis could have been up to 26 meters long - but these species have only been passed on through very fragmentary skeletons.

A complete skull is only known from the species Mamenchisaurus youngi . This skull was extremely small in relation to the body - including the lower jaw, it was 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. Well-defined scleral rings around the eyes indicate a good sense of sight. The lower jaw was relatively deep at the front ( symphysis ) and showed a small opening at the side (external mandibular window) - this opening was closed in all other sauropods except Shunosaurus . The chisel-like teeth were close together. In the upper jaw there were between 14 and 18 teeth on each side and 4 teeth in the premaxillary located in front of the upper jaw . The lower jaw, meanwhile, contained between 18 and 24 teeth on each side.

The spine consisted of 18 to 19 cervical vertebrae, 12 vertebrae, 4 to 5 sacral vertebrae and over 50 caudal vertebrae. The neck was one of the relatively longest of all sauropods and was more than three times as long as the body, the largest known specimen of Mamenchisaurus hochuanensis measured the neck over 9.8 meters in length. Only the remains of the related genus Omeisaurus suggest an even longer neck in relation to the total length. The cervical vertebrae were characterized by very long cervical ribs , which ran down the cervical spine and reached a length of up to 4.1 meters in Mamenchisaurus sinocanadorum . Whether Mamenchisaurus just kept its neck horizontal or was able to straighten it up like a giraffe in order to be able to graze at greater heights is a matter of dispute. A more recent biomechanical study notes, however, that the neck was too immobile to straighten because of the very long neck ribs - unlike representatives of the Diplodocidae , whose neck was significantly more mobile and possibly allowed it to be straightened. The spine resembled that of the Diplodocidae in other features: the spinous processes of the posterior cervical and anterior vertebrae were bifurcated; in addition, the middle caudal vertebrae bore typical double-bar-like chevron bones .

The vertebrae in front of the sacrum were opisthocoel , that is, convex on the front and concave on the back. The caudal vertebrae close to the body showed the opposite constellation ( procoel - concave on the front and convex on the rear), while the middle caudal vertebrae were amphiplat (flat on the front and rear). Further features relevant to the delimitation of the genus can also be found in the shoulder girdle and the extremities: The shovel-like lower end of the shoulder blade was enlarged, the entire bone was longer than the thigh bone. The sternum was small and roughly round. The length ratio between the front and rear legs was about 3/4 to 4/5, both the front and rear feet were relatively small.

Cladogram , simplified according to Sander and colleagues (2010):
  Sauropoda  

 Antetonitrus


     

 Vulcanodon


     

 Spinophorosaurus


  Eusauropoda 

 Shunosaurus


     

 Barapasaurus


     

 Patagosaurus


     
  Mamenchisauridae  

 Mamenchisaurus


   

 Omeisaurus



     

 Cetiosaurus


     

 Jobaria


   

 Neosauropoda











Template: Klade / Maintenance / Style
Systematic position of Mamenchisaurus according to Sander and colleagues (2010)

Systematics

External system

The systematic classification of Mamenchisaurus is controversial. John McIntosh (1990) considered the genus to be a representative of the Diplodocidae , based on the double-bar-like chevron bones, the forked spinous processes and the procoel caudal vertebrae. Later it turned out, however, that these characteristics are not only found in representatives of the Diplodocidae, but also in many other sauropod groups. Paul Upchurch (1995, 1998, 1999), however , assigned Mamenchisaurus to the Euhelopodidae - this grouping is now considered paraphyletic , since Euhelopus is only distantly related to Mamenchisaurus .

Today Mamenchisaurus is considered to be an original representative of the Eusauropoda , which, however, lacked important features of the more advanced sauropods ( Neosauropods ) and which is therefore outside of the Neosauropoda. Often Mamenchisaurus is classified together with presumably closely related forms within a group called Mamenchisauridae . Which genera are to be assigned to this group in addition to Mamenchisaurus is disputed - however, the genera Chuanjiesaurus , Eomamenchisaurus , Tienshanosaurus , Tonganosaurus , Omeisaurus and Yuanmousaurus are often placed in this group.

Internal system

Paul Upchurch (2004) notes that the internal system of Mamenchisaurus is very confusing and that the genus needs revision. Many of the finds known as Mamenchisaurus cannot be assigned to this genus with certainty (trash taxon).

Six species are currently recognized; some studies list a possible seventh species, Mamenchisaurus fuxiensis , but its 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 which belonged to 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 known from at least five skeletons, one of these specimens includes remains of the skull. A completely traditional neck consists of 19 cervical vertebrae. The largest specimen is estimated to be 22 meters long. The skeletons come from the Shangshaximiao Formation of Hechuan and Zigong in Sichuan and from the Hengtang Formation of Yongdeng in Gansu .
  • Mamenchisaurus sinocanadorum Russell & Zheng, 1994 : A very large species known only from a series of cervical vertebrae with an incomplete skull that comes from the Shishugou formation of Jungger in Xinjiang .
  • Mamenchisaurus youngi Pi, Ouyang & Ye, 1996 : A single, but almost complete skeleton with a complete skull is known of this species. This specimen is estimated to be 16 meters long. It comes from the Shangshaximiao Formation of Zigong in Sichuan.
  • Memenchisaurus anyuensis He et al. , 1996 : One relatively complete and four incomplete skeletons are known, which are estimated to be about 21 to 23 meters in length. These finds come from the Penglaizheng Formation of Anyue in Sichuan.
  • Mamenchisaurus jingyanensis Zhang, Li & Zeng, 1998 : This species is known for having three incomplete skeletons - one of these skeletons includes an incomplete skull. The length of these specimens is estimated to be 20 to 26 meters. The finds come from the Shangshaximiao Formation of Jingyan in Sichuan.
  • Mamenchisaurus fuxiensis (Hou, Zhao, & Chao, 1976) : This problematic species was originally described as a separate genus - Zigongosaurus . However, it may be a species of Omeisaurus or Mamenchisaurus . The only find consists of various, disjointed bones from the Shangshaximiao Formation of Zigong in Sichuan.

supporting documents

literature

  • Donald F. Glut : Dinosaurs. The Encyclopedia. McFarland, Jefferson NC et al. 1997, ISBN 0-89950-917-7 .
  • Heinrich Mallison: Rearing giants - kinetic / dynamic modeling of sauropod bipedal and tripodal poses. In: P. Martin Sander , Andreas Christian, Marcus Clauss, Regina Fechner, Carole T. Gee, Eva-Maria Griebeler, Hanns-Christian Gunga , Jürgen Hummel, Heinrich Mallison, Steven F. Perry, Holger Preuschoft, Oliver WM Rauhut , Kristian Remes, Thomas Tütken, Oliver Wings, Ulrich Witzel (Eds.): Biology of the sauropod dinosaurs. Understanding the life of giants. Indiana University Press, Bloomington IN et al. 2011, ISBN 978-0-253-35508-9 , pp. 237-250.
  • John S. McIntosh: Sauropoda. In: David B. Weishampel , Peter Dodson , Halszka Osmólska (eds.): The Dinosauria . University of California Press, Berkeley CA et al. 1990, ISBN 0-520-06726-6 , pp. 345-401.
  • Ouyang Hui, Ye Yong: The first mamenchisaurian skeleton with complete skull Mamenchisaurus Youngi. Sichuan Science and Technology Press, Chengdu 2001, ISBN 7-5364-4871-6 , p. 90.
  • Oliver WM Rauhut, Regina Fechner, Kristian Remes, Katrin Reis: How to Get Big in the Mesozoic: The Evolution of the Sauropodomorph Body Plan. In: P. Martin Sander, Andreas Christian, Marcus Clauss, Regina Fechner, Carole T. Gee, Eva-Maria Griebeler, Hanns-Christian Gunga, Jürgen Hummel, Heinrich Mallison, Steven F. Perry, Holger Preuschoft, Oliver WM Rauhut, Kristian Remes, Thomas Tütken, Oliver Wings, Ulrich Witzel (Eds.): Biology of the sauropod dinosaurs. Understanding the life of giants. Indiana University Press, Bloomington IN et al. 2011, ISBN 978-0-253-35508-9 , pp. 119-149.
  • P. Martin Sander, Andreas Christian, Marcus Clauss, Regina Fechner, Carole T. Gee, Eva-Maria Griebeler, Hanns-Christian Gunga, Jürgen Hummel, Heinrich Mallison, Steven F. Perry, Holger Preuschoft, Oliver WM Rauhut, Kristian Remes, Thomas Tütken, Oliver Wings, Ulrich Witzel: Biology of the sauropod dinosaurs: the evolution of gigantism. In: Biological Reviews. Vol. 86, No. 1, 2011, ISSN  0006-3231 , pp. 117-155, doi : 10.1111 / j.1469-185X.2010.00137.x .
  • Toru Sekiya: Re-examination of Chuanjiesaurus anaensis (Dinosauria: Sauropoda) from the Middle Jurassic Chuanjie Formation, Lufeng County, Yunnan Province, Southwest China. In: Memoir of the Fukui Prefectural Dinosaur Museum. No. 10, 2011, ISSN  1347-5622 , pp. 1–54, here p. 3, digitized version (PDF; 6.26) .
  • Paul Upchurch , Paul M. Barrett , Peter Dodson: Sauropoda. In: David B. Weishampel, Peter Dodson, Halszka Osmólska (eds.): The Dinosauria . 2nd edition. University of California Press, Berkeley CA et al. 2004, ISBN 0-520-24209-2 , pp. 259-324.
  • CC Young, HC Chao: [Mamenchisaurus hochuanensis sp. nov.]. In: Szechuan Academica Sinica. Institute of Vertebrate Palaeontology and Palaeoanthropology. Monographs. Series A, Vol. 8, 1972, pp. 1–30, (In Chinese language and writing; English translation: (PDF; 334.17 kB) ).

Individual evidence

  1. ^ Gregory S. Paul: The Princeton Field Guide To Dinosaurs. Princeton University Press, Princeton NJ et al. 2010, ISBN 978-0-691-13720-9 , pp. 181-184, online .
  2. ↑ Upchurch et al. 2004 , p. 318
  3. ↑ Sander et al. 2010 , p. 11
  4. ↑ a b Upchurch et al. 2004 , p. 262
  5. ↑ Ouyang and He 2002 , p. 98
  6. ↑ Origin of the name Mamenchisaurus ( Memento of September 27, 2007 in the Internet Archive ) (in Chinese), website of the Beijing Natural History Museum
  7. ↑ Sander et al. 2010 , p. 6
  8. ↑ a b c d e f g h i Ouyang and He 2002 , p. 99
  9. ↑ a b c d Ouyang and He 2002 , pp. 100-101
  10. ↑ Ouyang and He 2002 , p. 92
  11. ↑ a b Ouyang and He 2002 , p. 122
  12. ↑ a b Ouyang and He 2002 , pp. 102-103
  13. ↑ a b c d Ouyang and He 2002 , pp. 90–91
  14. ↑ Upchurch et al. 2004 , p. 278
  15. ↑ Glut 1997 , p. 575
  16. ↑ Ouyang and He 2002 , p. 101
  17. ^ Mallison 2011
  18. ↑ Sander et al. 2010 , p. 25
  19. ↑ a b McIntosh 1990 , p. 394
  20. ↑ Sander et al. 2010 , p. 10
  21. ↑ a b Upchurch et al. 2004 , pp. 300-301
  22. ↑ Sekiya 2011 , p. 1
  23. ↑ Young & Zhao 1972 , p. 3

Web links

Commons : Mamenchisaurus  - collection of images, videos and audio files