Ornitholestes
| Ornitholestes | ||||||||||||
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Skeleton in the American Museum of Natural History |
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| Temporal occurrence | ||||||||||||
| Upper Jurassic ( Kimmeridgian to Tithonian ) | ||||||||||||
| 157.3 to 145 million years | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Ornitholestes | ||||||||||||
| Osborn , 1903 | ||||||||||||
Ornitholestes is a theropod dinosaur belonging to the Coelurosauria group . It was a small, bipedal carnivore, the remains of which were found in the strata of the Morrison Formation (later Jurassic ) in the northwestern United States . The only species assigned to this genus is Ornitholestes hermanni . Ornitholestes is one of the popular smaller dinosaurs.
features
Ornitholestes was about two meters long and 15 to 20 kilograms, with the tail making up about half the body length. Compared to the related Coelurus , it has a fairly short neck and body. The lower leg bones are unusually short - this is probably why he was not as fast a runner as other, similar theropods.
The skull is quite small and compact compared to other theropods of its size. Very often Ornitholestes was depicted with a small, leaf-shaped comb or horn over the nostrils. However, recent studies have refuted such a headdress: After the skull was thoroughly dissected again, it was discovered that it was somewhat dented, which had displaced the left nasal bone and was misinterpreted as a headdress.
A special feature that Ornitholestes shares with Proceratosaurus is heterodontics : the teeth of the front half of the jaw are significantly smaller and more conical than those of the rear half of the jaw.
Finds and find history
The holotype material (AMNH 619) is a partial skeleton, which among other things, a quite complete skull, the large part of the vertebrae, pelvic bones, an incomplete thigh bone (femur), a part of the fibula (fibula), various toe bone (metacarpal), two Upper arm bone ( humerus ), and various fragments. More recent finds from Wyoming could also be attributed to the Ornitholestes .
In the past, hand bones found in isolation were also believed to belong to the Ornitholestes (Osborn, 1916). However, in 2005 Carpenter and others attributed this hand to Tanycolagreus , another small carnivore of the Morrison formation, due to great similarities .
The skeleton was discovered in the "Bone Cabin Quarry", 13 kilometers north of Como Bluff . Como Bluff, a dinosaur cemetery of the Morrison Formation, is one of the most important sites for dinosaurs - this is also where the Coelurus , related to Ornitholestes , was discovered ( Marsh , 1879). Ornitholestes was named in a brief description by Henry Fairfield Osborn in 1903 , and a more extensive description followed in 1916. Osborn chose the name Ornitholestes , which means something like "bird robber", because he imagined an active, fast hunter.
In 1920, Gilmore ascribed Ornitholestes to Coelurus , since the researcher believes that the vertebrae of the two species show only minimal differences. It was not until 1980 that the various differences between the two species were recognized (Ostrom, 1980), and Ornitholestes was again considered an independent genus.
In 2005 there was a new description of Coelurus and Ornitholestes .
literature
- Henry Fairfield Osborn : Ornitholestes hermanni, a new compsognathoid Dinosaur from the Upper Jurassic. In: Bulletin of the American Museum of Natural History. Vol. 19, 1903, pp. 459-464, (PDF; 3.5 MB).
- Kenneth Carpenter , Clifford Miles, John H. Ostrom , Karen Cloward: Redescription of the small maniraptoran theropods Ornitholestes and Coelurus from the Upper Jurassic Morrison Formation of Wyoming. In: Kenneth Carpenter (Ed.): The Carnivorous Dinosaurs. Indiana University Press, Bloomington 2005, ISBN 0-253-34539-1 , pp. 49-71.
Individual evidence
- ↑ a b Kenneth Carpenter, Clifford Miles, John Ostrom, Karen Cloward: Redescription of the small maniraptoran theropods Ornitholestes and Coelurus from the Upper Jurassic Morrison Formation of Wyoming. In: Kenneth Carpenter (Ed.): The Carnivorous Dinosaurs. Indiana University Press, Bloomington 2005, ISBN 0-253-34539-1 , pp. 49-71.
