Erlikosaurus
| Erlikosaurus | ||||||||||||
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Live reconstruction of Erlikosaurus with primitive feathers like those found in Beipiaosaurus . |
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| Temporal occurrence | ||||||||||||
| Upper Cretaceous ( Cenomanium to Santonium ) | ||||||||||||
| 100.5 to 83.6 million years | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Erlikosaurus | ||||||||||||
| Pearl , 1980 | ||||||||||||
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Erlikosaurus is a genus of theropod dinosaur in the Therizinosauridae family. Fossils of the animal, consisting of a well-preserved skull and the only partially preserved remaining skeleton, were found in sedimentary rocks of Mongolia thatwere around 100 to 84 million years old.
description
skull
The Erlikosaurus skull is the best preserved skull of all therizinosaurs. The skull was long, low, and heavily pneumatized. The nostrils were large. The bones of the skull, especially in front of the eyes, and the skull were thin. The premaxillary was formed into a broad, toothless beak, which was possibly covered with horn on the outside. The premaxillary nasal process was narrow and long, the subnasal process short.
The maxillary formed the posterior and lower boundaries of the outer nostrils. It still had 24 small, uniform teeth on the region under the lower skull window . They were straight and narrow, pointed and flattened on the sides. With the exception of the five in the middle, they were close together. The crowns of the teeth were sawed in front and behind, and the roots of the teeth were cylindrical.
The lower jaw, which was toothless in the anterior part, was flat, the anterior end pointed downwards, as in all other known therizinosaurs lower jaws. Each half of the lower jaw had 31 teeth that resembled those of the upper jaw. The first five were taller and farther apart. The rear sat close together. The lip-facing surface of the posterior teeth was convex. All teeth of the lower jaw had cylindrical roots and sawn edges.
It is believed that Erlikosaurus had a beak.
Remaining skeleton
Only a few parts of the rest of the skeleton are known. However, they show that the skull was small compared to the body for a theropod. The cervical vertebrae were large and elongated. The ribs of the cervical spine had grown together with the vertebrae.
The phalangeal formula for the foot is 2,3,4,5,0. Erlikosaurus had four toes and not the tridactyl (three-toed) foot of the other theropods. The first toe was the shortest, the second and third the largest and the same length. The fourth was slimmer than anyone else. The foot claws were large, curved and strongly flattened perpendicular to the longitudinal axis of the body.
literature
- James M. Clark , Teresa Maryańska , Rinchen Barsbold : Therizinosauroidea. 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. 151-164, doi : 10.1525 / california / 9780520242098.003.0009 .
Individual evidence
- ↑ Stephan Lautenschlager, Lawrence M. Witmer , Perle Altangerel , Emily J. Rayfielda: Edentulism, beaks, and biomechanical innovations in the evolution of theropod dinosaurs. In: Proceedings of the National Academy of Sciences . Vol. 110, No. 51, 2013, pp. 20657-20662, doi : 10.1073 / pnas.1310711110 .