Jeholosaurus

Jeholosaurus
Skeletal reconstruction of Jeholosaurus on display at the Dinosaurland Fossil Museum in Lyme Regis
Temporal occurrence
Lower Cretaceous ( Barremium )
130.7 to 126.3 million years
Locations
Liaoning , China ( Jehol Group )
Systematics
Dinosaur (dinosauria) Pelvic dinosaur (Ornithischia) Cerapoda Ornithopoda Jeholosaurus
Scientific name
Jeholosaurus
Xu , Wang & You , 2000
Art
Jeholosaurus shangyuanensis

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

The skeletons come from the Yixian Formation ( Jehol Group ), an important fossil deposit that is particularly famous for its fossils of feathered dinosaurs and birds. Jeholosaurus is an original representative of the ornithopods. The only species is Jeholosaurus shangyuanensis .

Naming

The name refers to Jehol, an outdated term for western Liaoning and northern Hebei. The second part of the species name, shangyuanensis , is derived from Shangyuan , a geographical name for the region in which the site is located.

features

The body length of Jeholosaurus is estimated at about 0.8 meters, the weight at about 3 kilograms. Its skull, a total of 6 cm long, has a beak and leaf-shaped teeth. The snout is relatively short and made up only about 40% of the total length of the skull; the eye sockets, on the other hand, are large and as long as the snout. In the premaxillary , a jawbone located in front of the upper jaw, there were 6 teeth on each side. There were 13 teeth in each of the upper jaws, the number of teeth in the lower jaw is unknown. The teeth are heterodontic , so there were differently formed groups of teeth: the teeth of the intermaxillary bone were relatively slender, slightly curved and unsawed, while the teeth of the upper jaw were fan-shaped and serrated. The teeth of the lower jaw were also sawed. Important features of the residual skeleton can be found in the foot: The metatarsal bones were not arranged on one level; in addition, the fourth phalanx of the third toe was longer than the other phalanges of that toe.

Jeholosaurus is an original representative of the ornithopods and shows an interesting combination of original and advanced features, which is why this genus is important in understanding the early evolution of the ornithopods. For example, the external mandibular window, a lateral opening in the lower jaw, is closed, as is the case with all more advanced ornithopods. In addition, the predentale , a bone in front of the lower jaw that forms the bony base of the lower beak, was relatively long: This could indicate that the seam of the lower jaw ( symphysis ) was immobile, as in ceratopsians . At the same time, the skeleton shows a number of original features that are missing in all other ornithopods: Among them are the 6 teeth of the premaxillary, and there was a small gap ( diastema ) between the rows of teeth of the premaxillary and the upper jaw .

Main literature

• Xing Xu , Xiao-Lin Wang, Hai-Lu You: A Primitive Ornithopod from the Early Cretaceous Yixian Formation of Liaoning. In: Vertebrata PalAsiatica. Vol. 38, No. 4, 2000, ISSN  1000-3118 , pp. 318-325, digitized version (PDF; 903.81 kB) .

Supplementary literature

• The great Ravensburger Atlas of the dinosaurs. Ravensburger Buchverlag Otto Maier GmbH, Ravensburg 2004, ISBN 3-473-35855-X .
• Mee-mann Chang (Ed.): The Jehol Fossils. The Emergence of Feathered Dinosaurs, Beaked Birds and Flowering Plants. Academic Press, Amsterdam et al. 2008, ISBN 978-0-12-374173-8 .
• Joachim Künzel: Dinosaurs. (Fascinating giants of prehistoric times). Edition XXL GmbH, Fränkisch-Crumbach 2009, ISBN 978-3-89736-343-4 .

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 , p. 275, online ( memento of the original of July 13, 2015 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. .