Jeholosaurus

Skeletal reconstruction of Jeholosaurus exhibited in the Dinosaur Fossil Country Museum in Lyme Regis

  • Liaoning, China ( Jehol Group)
  • Jeholosaurus shangyuanensis

Jeholosaurus is a genus of small ornithopoder dinosaurs. So far, two fragmentary skeletons are known, which were found in the Chinese province of Liaoning and the Lower Cretaceous (Lower Barremian ) be dated.

The skeletons are from the Yixian Formation ( Jehol Group), an important fossil site, which is famous in particular for its fossils of feathered dinosaurs and birds. Jeholosaurus is an original representative of the ornithopod. The only way is Jeholosaurus shangyuanensis.

Naming

The name refers to Jehol, an obsolete term for the western Liaoning and northern Hebei. The second part of the species name, shangyuanensis, comes from Shang Yuan, a geographical name of the region in which the locality is situated.

Features

The body length of Jeholosaurus is estimated to about 0.8 m, the weight of approximately 3 kg. His skull, a total of 6 inches long, has a beak and leaf-shaped teeth. The snout is made ​​relatively short and only about 40% of the total length of the head from; the eye sockets, however, are large and as long as the snout. In the premaxilla, one situated in front of the upper jaw, jawbone, sat on each side 6 teeth. In the upper jaw itself sat each with 13 teeth, the number of teeth in the lower jaw is unknown. The dentition is heterodont, so there were variously trained dental groups exist: For example, the teeth of the premaxillary bone were relatively slender, slightly curved and ungesägt, while the teeth of the upper jaw were fan-shaped and serrated. The teeth of the lower jaw were also cut. Important features of the rest of the skeleton can be found in the foot: To the metatarsal bones were not arranged on a plane; also the fourth phalanx of the third toe was longer than other phalanges of this toe.

Jeholosaurus is an original representative of the ornithopod and shows an interesting combination of original and advanced features, which is why this genus for understanding the early evolution of ornithopod important. For example, the external Mandibularfenster, a lateral opening at the lower jaw is closed, as in all advanced ornithopod. In addition, the Praedentale, a present in front of the lower jaw bone that forms the bony base of the lower mandible was relatively long: This could indicate that the interface of the mandible ( symphysis ) was immovable, as in Ceratopsiern. At the same time, the skeleton shows a number of original features that are missing in all other ornithopods: Below are the six teeth of the premaxilla, also was located between the rows of teeth of the premaxilla and maxilla, a small gap ( diastema ).

Main literature

  • Xing Xu, Xiao- Lin Wang, Hai - Lu You: A primitive Ornithopod from the Early Cretaceous Yixian Formation of Liaoning. In: Vertebrata PalAsiatica. 38, No. 4, 2000, pp. 318-325 (PDF).

Supplementary literature

  • Mee -mann Chang: The Jehol Fossils, The Emergence of Feathered Dinosaurs, Beaked Birds and Flowering Plants, Academic Press, Amsterdam, Boston, Heidelberg, London, New York, Oxford, Paris, San Diego, San Francisco, Singapore, Sydney, Tokyo, 2003, ISBN 978-0-12-374173-8
  • Joachim Kuenzel: dinosaurs, fascinating giants of old, Edition XXL GmbH, Fränlisch -Crumbach, 2009, ISBN 978-3-89736-343-4
  • The big Ravensburger Atlas of the dinosaurs, Ravensburger Verlag Otto Maier GmbH, Ravensburg, 2004, ISBN 3- 473-35855 -X
Mya (unit) Cerapoda Yixian-Formation
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