Dromaeosaurus
| Dromaeosaurus | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Skull cast of Dromaeosaurus albertensis |
||||||||||||
| Temporal occurrence | ||||||||||||
| Upper Cretaceous (late Campanium to late Maastrichtian ) | ||||||||||||
| 76.4 to 66 million years | ||||||||||||
| Locations | ||||||||||||
| Systematics | ||||||||||||
|
||||||||||||
| Scientific name | ||||||||||||
| Dromaeosaurus | ||||||||||||
| Matthew & Brown , 1922 | ||||||||||||
| Art | ||||||||||||
|
Dromaeosaurus was a genus of carnivorous dinosaurs belonging to the Dromaeosauridae group that lived during the Late Upper Cretaceous North America . The only widely recognized species is Dromaeosaurus albertensis , although other species have been described. Dromaeosaurus albertensis is based on a fragmentary skull and a few foot bones that were discovered by William Diller Matthew and Barnum Brown as early as 1914; thus Dromaeosaurus is the first Dromaeosauridae to be discovered. This find comes from the Dinosaur Park Formation of Alberta ( Canada ) and is dated to the Upper Cretaceous (late Campanian to Maastrichtian ).
Other, very fragmentary remains come from Montana and Alaska . Within the Dromaeosauridae, Dromaeosaurus is usually classified in its own subfamily, the Dromaeosaurinae, often together with Utahraptor and Achillobator . Although few fossils are known, Dromaeosaurus is a publicly known Dromaeosauridae that appears in many popular books about dinosaurs and has skeletal reconstructions on display in museums around the world.
features
Dromaeosaurus is estimated to be about 1.8 meters long and weigh about 15 kg. Compared to other dromaeosaurids, the skull was more robust, the teeth larger and the row of teeth at the tip of the snout wider. In contrast to other dromaeosaurids, the skull was not pneumatized (filled with cavities). As with Deinonychus , the jaw was sturdy and deep, in contrast to the long and narrow jaw of Velociraptor . On each side of the lower jaw (dental) there were 11 teeth, on each side of the upper jaw (maxillary) there were 9 teeth. There are also four teeth of the paired intermaxillary bone (premaxillary) that sat in front of the upper jaw; these teeth were smaller and straighter than those of the upper jaw. In total, Dromaeosaurus had 48 teeth. The longest teeth of the upper jaw were over 1.5 cm long, while the longest teeth of the lower jaw were 1.4 cm long (tooth crown + tooth root). The teeth were sawn on the front edge and on the rear edge - while there were 34 denticles (teeth) on the front edge of each tooth, there were 45 denticles on the rear edge. The denticles were short and wide in Dromaeosaurus and other Dromaeosaurinen, while they were long and hook-like in Velociraptorinen. The row of denticles is at the tip of the tooth near the center line of the tooth, but then runs to the lingual (tongue-side) side of the tooth. This is an important trait that can be used to identify Dromaeosaurus teeth.
It is not known whether Dromaeosaurus, like many other dromaeosaurids, had an enlarged sickle claw on the second (inner) toe. The phalanges of the second toe, however, were more robust than those of Deinonychus , Velociraptor and Saurornitholestes , and were similar to those of the related genus Adasaurus . Adasaurus, however, only had a reduced sickle claw that was no larger than the claws of the rest of the toes; this could indicate that Dromaeosaurus did not have an enlarged sickle claw either.
nutrition
A biomechanical study by François Therrien and colleagues (2005) found that Dromaeosaurus had a stronger bite force than other Dromaeosaurids. The Dromaeosaurus bite was stronger than that of Deinonychus and three times as strong as Velociraptor . Therrien and colleagues conclude from their results that dromaeosaurus and perhaps also other dromaeosaurins showed a different hunting behavior than the narrow-snouted velociraptorins: Dromaeosaurus could have wounded its prey with powerful bites, while velociraptorins could have relied more on their sickle claws. According to the researchers, the jaws of Dromaeosaurus were not suitable for holding strong prey.
Research history
The first remains were discovered by the eminent paleontologist Barnum Brown in 1914 near the Red Deer River in the Canadian province of Alberta during an expedition to the American Museum of Natural History . Today the site is known as Little Sandhill Creek and is within Dinosaur Provincial Park . These rocks come from the Campanium and belong to the Dinosaur Park Formation. The find ( holotype , specimen number AMNH 5356) consists of a 24 cm long fragmentary skull, some toe bones and a left metatarsal (metatarsal I). On this basis, Brown and William Diller Matthew (1922) present the new genus Dromaeosaurus with the type species Dromaeosaurus albertensis in a preliminary publication . Since the skull was incomplete and not yet fully prepared, they announced a more extensive description that would appear in a later article. Matthew and Brown assigned Dromaeosaurus together with Gorgosaurus , Albertosaurus and Tyrannosaurus to the family Deinodontidae (now Tyrannosauridae ). Nevertheless, they considered the differences to other Deinodontiden to be large enough to classify Dromaeosaurus within the Deinodontidae in a separate subfamily, the Dromaeosaurinae. The name Dromaeosaurus means something like "running lizard" ( Gr .: Δρομεύς / dromeus = "run", σαῦρος / sauros = "lizard") and is intended to indicate an animal that, in contrast to other deinodontids, was small and light.
A full description of the find was not published until 1969 by Colbert and Russell. In the meantime, the skull has been prepared for exhibitions, with missing elements being supplemented with colored plaster of paris and glue, which made the description difficult - the modeled elements covered anatomical details; sometimes the reconstruction was so good that it was difficult to distinguish real from artificial elements. Later, as described by Colbert and Russell, the skull was damaged. The skull roof, consisting mainly of modeled elements, was separated from the rest of the skull, the fragment of the parietal bone (parietal) was lost. However, the damage also exposed features that were previously not visible. After another preparation, in which almost all modeled elements as well as the remaining rock matrix were removed, Philip Currie published a further, supplementary description in 1995, which is based in part on a computer tomography scan of the skull.
Apart from the holotype skeleton, only a few fragmentary bones are known. Finds from the Judith River Group of Alberta and Montana include an isolated frontal (copy number NMC 12349), a fragmentary dental and 30 isolated teeth. Cope (1876) originally described some teeth from the Dinosaur Park Formation as Laelaps explanatus , but possibly belonged to Dromaeosaurus and are sometimes listed as a separate species, Dromaeosaurus explanatus . A phalanx, a claw and various isolated dentals were once attributed to Dromaeosaurus , but actually belonged to the related Saurornitholestes langstoni . A partial metatarsus from the Laramie Formation of Colorado was originally described as Ornithomimus minutus (Marsh, 1892), but then described by Russell (1972) as another possible species of Dromaeosaurus , Dromaeosaurus minutus . Today this species is considered to be the noun dubium (dubious name). Other remains that could possibly belong to Dromaeosaurus come from the Prince Creek Formation of Alaska and are about 66 million years old ( Maastrichtian ).
Individual evidence
- ↑ a b c Mark A. Norell , Peter Makovicky : Dromaeosauridae. 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. 196-209.
- ↑ 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 .
- ^ François Therrien, Donald M. Henderson: My theropod is bigger than yours ... or not: estimating body size from skull length in theropods. In: Journal of Vertebrate Paleontology. Vol. 27, No. 1, 2007, ISSN 0272-4634 , pp. 108-115, doi : 10.1671 / 0272-4634 (2007) 27 [108: MTIBTY] 2.0.CO; 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; 184.08 kB) .
- ^ A b c François Therrien, Donald M. Henderson, Christopher B. Ruff: Bite Me: Biomechanical models of theropod mandibles and implications for feeding. In: Kenneth Carpenter (Ed.): The Carnivorous Dinosaurs. Indiana University Press, Bloomington IN et al. 2005, ISBN 0-253-34539-1 , pp. 179-237.
- ^ A b c d Philip J. Currie: New information on the anatomy and relationships of Dromaeosaurus albertensis (Dinosauria: Theropoda). In: Journal of Vertebrate Paleontology. Vol. 15, No. 3, 1995, pp. 576-591, doi : 10.1080 / 02724634.1995.10011250 .
- ^ Philip J. Currie, J. Keith Rigby Jr., Robert E. Sloan: Theropod teeth from the Judith River Formation of southern Alberta, Canada. In: Kenneth Carpenter, Philip J. Currie (Eds.): Dinosaur systematics. Approaches and perspectives. Cambridge University Press, Cambridge et al. 1990, ISBN 0-521-36672-0 , pp. 107-125.
- ^ William D. Matthew , Barnum Brown : The family Deinodontidæ, with notice of a new genus from the Cretaceous of Alberta. In: Bulletin of the American Museum of Natural History. Vol. 46, Article 6, 1922, pp. 367-385, digital version (PDF; 1.74 MB) .
- ↑ Ben Creisler: Dinosauria Translation and Pronunciation Guide ( Memento of October 13, 2011 in the Internet Archive )
- ^ A b Donald F. Glut : Dinosaurs. The Encyclopedia. McFarland, Jefferson NC et al. 1997, ISBN 0-89950-917-7 .
