Atacamatitan
| Atacamatitan | ||||||||||||
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| Upper Chalk | ||||||||||||
| 100.5 to 66 million years | ||||||||||||
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| Scientific name | ||||||||||||
| Atacamatitan | ||||||||||||
| Kellner et al., 2011 | ||||||||||||
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Atacamatitan is a genus of sauropod dinosaur from the group of titanosaur . So far, only a single, very fragmentary skeleton is known, which was found in the Atacama Desert in northern Chile and is dated to the Upper Cretaceous . Like all sauropods, Atacamatitan was a large, quadruped (four-footed) herbivore with a long neck and tail. This genus wasfirst described scientificallyin 2011 with the only species , Atacamatitan chilensis , by researchers working with Alexander Kellner .
features
The front legs were more powerfully built than the rear legs. With a length of 1.1 m and a shaft thickness of only 12.5 cm (measured halfway up the bone), the thigh bone was built relatively gracefully. Still, the humerus was longer than that of many other derived (advanced) titanosaurs such as Saltasaurus . The thickness of the thighbone shaft decreases evenly in Atacamatitan , unlike other representatives of the Titanosauria, in which the shaft thickness varies only slightly.
The vertebrae were clearly opisthocoel ( convex on the front and concave on the rear ), while hyposphene-hypantrum connections were absent, as in many other representatives of the Titanosauria. The vertebrae differed from other representatives by the lateral cavities (pleurocoele) of the vertebral bodies, which were rounder and shorter and not tapered forward, as well as by a strongly concave underside of the vertebral bodies . The caudal vertebrae, on the other hand, were procoel (concave on the front and convex on the rear), with no pleurocoele. In contrast to related genera, the caudal vertebrae had a laterally flattened spinous process with a blade-shaped front edge.
Systematics
The exact relationships of this genus are unknown. However, Atacamatitan seems to have been neither a particularly basic (original) nor a particularly derived (advanced) titanosaur. This genus was more basic than the representatives of the Saltasauridae , but more derived than Malawisaurus . At the same time belonging to the Aeolosaurini can be excluded.
Meaning, find, and discovery
Vertebrate fossils from Chile are relatively rare. Atacamatitan is the most complete find to date of a dinosaur from the Antofagasta region and one of the most fully preserved titanosaur finds from Chile. The find comes from the layers of the Tolar Formation , the age of which was previously unknown. Atacamatitan shows that this formation can be dated to the Upper Cretaceous and not to the Paleocene , which could not be ruled out beforehand.
The find ( holotype , specimen number SGO-PV-961) consists of a right thigh bone (femur), the lower end of an upper arm bone (humerus), vertebrae (two dorsal vertebrae and the anterior caudal vertebrae), ribs, a fragment of the sternum (sternum) and further, unidentifiable fragments. These fossils were excavated over an area of 2 m². They are reddish in color and very heavy due to high permineralization . Today they are in the collection of the Museo Nacional de Historia Natural in Santiago de Chile . The site is located near the city of Conchi Viejo in the Chilean region of Antofagasta.
The site was discovered in February 2000 during a joint expedition by Brazilian and Chilean researchers, who first became aware of the thighbones exposed on the surface. However, the skeleton could only be recovered during a second expedition in July of the following year. The find was scientifically described in 2011 by researchers working with the Brazilian paleontologist Alexander Kellner. The name Atacamatitan chilensis refers to the place where it was found and points to the Atacama Desert and Chile. The ending -titan , which is used for numerous titanosaurs, refers to the titans of Greek mythology .
literature
- Alexander WA Kellner, David Rubilar-Rogers, Alexander Vargas, Mario Suárez: A new titanosaur sauropod from the Atacama Desert, Chile. In: Anais da Academia Brasileira de Ciências. Vol. 83, No. 1, 2011, ISSN 0001-3765 , pp. 211-219, doi : 10.1590 / S0001-37652011000100011 , digital version (PDF; 1.7 MB) .