Atrociraptor

Atrociraptor
	Fragmentary skull of Atrociraptor
Temporal occurrence
	Upper Cretaceous (late Campanium ) to early Maastrichtian
	76.4 to 69.9 million years
Locations
	Alberta , Canada ( Horseshoe Canyon Formation );
Systematics
	Lizard dinosaur (Saurischia)
	Theropoda
	Maniraptora
	Deinonychosauria
	Dromaeosauridae
	Atrociraptor
Scientific name
	Atrociraptor
	Currie & Varricchio , 2004
Art
	Atrociraptor marshalli;

Atrociraptor was a genus of carnivorous dinosaurs from the Dromaeosauridae group . So far only one fragmentary skull is known, which was discovered in the Horseshoe Canyon Formation of Alberta ( Canada ) and isdatedin the Upper Cretaceous (late Campanium to early Maastrichtian ).

Atrociraptor reached a length of about 1.8 meters.

features

The fragmentary skull found consists of the right upper jaw (maxillary), the right complete right dental (the tooth-bearing part of the lower jaw), parts of the left dental, two intermaxillary bones (premaxillary) and numerous bone fragments. In contrast to other dromaeosaurids, the skull was unusually short and high. The basic body of the intermaxillary bone sitting in front of the upper jaw was higher than it was wide, similar to Deinonychus . The teeth were more curved back than in other dromaeosaurids except Bambiraptor and Deinonychus . The teeth of the upper jaw were all about the same size. In addition, the maxillary window was larger than with other dromaeosaurids and was located directly above the promaxillary window, while with all other dromaeosaurids it was behind the latter.

The teeth were flat and blade-like, with the teeth of the lower jaw generally smaller than those of the upper jaw. The denticles (teeth) were larger and less numerous on the posterior incisal edge of the teeth than on the anterior incisal edge, similar to other dromaeosaurids. In the intermaxillary bone there were four teeth on each side, as in other dromaeosaurids. Each upper jaw had 11 teeth. The number of teeth in the lower jaw cannot be precisely determined, but it is estimated that each lower jaw had 14 teeth. In total, Atrociraptor probably had 58 teeth. The upper jaw (maxilla) is 9.2 cm long and 4.5 cm high, of which the row of teeth makes up 8.5 cm. Thus the upper jaw as well as the intermaxillary bone is deeper than in other dromaeosaurids.

Systematics

Currie and Varicchio examined in their first description of atrociraptor the relationships of the new species, based on skull features. They concluded that Atrociraptor was most closely related to Deinonychus and the second most closely related to Bambiraptor , and placed Atrociraptor within the Velociraptorinae, a subgroup of the Dromaeosauridae. This assignment is based on the denticles, which are smaller on the front of the teeth than on the back. A more recent study by Currie and Longrich (2009) classifies Atrociraptor together with Saurornitholestes and Bambiraptor within a new group, the Saurornitholestinae.

History of discovery and naming

The find ( holotype , copy number TMP 95.166.1) was discovered in 1995 by Wayne Marshall and prepared by Ken Kucher of the Royal Tyrrell Museum of Palaeontology . Marshall discovered jaw and tooth fragments on a hillside about three miles west of the Royal Tyrrell Museum of Palaeontology in Drumheller . The find was in a relatively hard, isolated block of sandstone surrounded by softer sands. The site is about five meters above the Daly coal seam number 7. Atrociraptor was scientifically described in 2004 by Philip J. Currie and David Varricchio . The name Atrociraptor is derived from the Latin words atroci - "cruel, brutal" and raptor "robber". The species name marshalli honors Wayne Marshall, the discoverer of the skull.

supporting documents

literature

Philip J. Currie , David J. Varicchio: A new Dromaeosaurid from the Horseshoe Canyon Formation (Upper Cretaceous) of Alberta, Canada. In: Philip J. Currie, Eva B. Koppelhus, Martin A. Shugar, Joanna L. Wright: Feathered dragons. Studies on the transition from dinosaurs to birds. Indiana University Press, Bloomington IN et al. 2004, ISBN 0-253-34373-9 , pp. 112-132, digital copy (PDF; 1.67 MB) .

Individual evidence

↑ Currie, Varicchio: A new dromaeosaurid from the Horseshoe Canyon Formation (Upper Cretaceous) of Alberta, Canada. 2004.
↑ Thomas R. Holtz Jr .: Supplementary Information. to: Thomas R. Holtz Jr .: Dinosaurs. The most complete, up-to-date Encyclopedia for Dinosaur Lovers of all ages. Random House, New York NY 2007, ISBN 978-0-375-82419-7 , online (PDF; 184 kB) .
↑ Nicholas R. Longrich, Philip J. Currie: A microraptorine (Dinosauria – Dromaeosauridae) from the Late Cretaceous of North America. In: Proceedings of the National Academy of Sciences of the United States of America . Vol. 106, No. 13, 2009, pp. 5002-5007, doi : 10.1073 / pnas.0811664106 .

[1] Currie, Varicchio: A new dromaeosaurid from the Horseshoe Canyon Formation (Upper Cretaceous) of Alberta, Canada. 2004.

[2] Thomas R. Holtz Jr .: Supplementary Information. to: Thomas R. Holtz Jr .: Dinosaurs. The most complete, up-to-date Encyclopedia for Dinosaur Lovers of all ages. Random House, New York NY 2007, ISBN 978-0-375-82419-7 , online (PDF; 184 kB) .

[currie_09-3] Nicholas R. Longrich, Philip J. Currie: A microraptorine (Dinosauria – Dromaeosauridae) from the Late Cretaceous of North America. In: Proceedings of the National Academy of Sciences of the United States of America . Vol. 106, No. 13, 2009, pp. 5002-5007, doi : 10.1073 / pnas.0811664106 .