Dromaeosaurus

Skull cast of Dromaeosaurus albertensis

• USA (Alaska, Prince Creek Formation, Montana, Judith River Formation )
• Canada ( Alberta, Dinosaur Park Formation, Scollard Formation)

• Dromaeosaurus albertensis

Dromaeosaurus was a genus of carnivorous dinosaur from the group of Dromaeosauridae that lived during the Late Cretaceous of North America. The only widely recognized species is Dromaeosaurus albertensis, although other species have been described. Dromaeosaurus albertensis based on a fragmentary skull and a few bones of the foot, which were discovered by William Diller Matthew and Barnum Brown in 1914; thus Dromaeosaurus the Dromaeosauridae first discovered. This find is from the Dinosaur Park Formation of Alberta (Canada) and is dated to the Late Cretaceous (late Campanian to Maastrichtian ).

Further, very fragmentary remains date back to Montana and Alaska. Within the Dromaeosauridae Dromaeosaurus is classified usually in a separate subfamily, the Dromaeosaurinae, often together with Utahraptor and Achillobator. Although few fossils are known Dromaeosaurus is known to the public Dromaeosauridae who appears in many popular books about dinosaurs and are issued by the skeletal reconstructions in museums around the world.

Features

Dromaeosaurus is estimated to have a length of about 1.8 meters and a weight of about 15 kg. Compared with other robust Dromaeosauriden the skull, teeth larger and the tooth row at the tip of the snout was wider. Unlike other Dromaeosauriden the cranium was not pneumatized ( crisscrossed with cavities ). As with Deinonychus the jaw was strong and deep, as opposed to the long and narrow jaw of Velociraptor. On each side of the lower jaw (dental ) were 11 teeth on each side of the upper jaw ( maxilla ), there were 9 teeth. There are also four teeth of the paired premaxillary bone ( premaxilla ), who was sitting in front of the upper jaw; these teeth were smaller and straighter than that of the upper jaw. Overall Dromaeosaurus thus had 48 teeth. The longest teeth of the upper jaw were about 1.5 cm long, while the longest teeth of the lower jaw were 1.4 cm long ( crown root ). The teeth were cut on the leading edge and the trailing edge - while on the front edge of each tooth 34 denticles ( teeth ) were sitting, they were on the trailing edge 45 denticles. The denticles were short and wide at Dromaeosaurus and other Dromaeosaurinen while they were at Velociraptorinen long and hook-like. The Dentikelreihe is close to the tooth tip of the center line of the tooth, but then runs on the lingual ( tongue side ) side of the tooth. This is an important feature that can be identified with the Dromaeosaurus teeth.

It is not known whether Dromaeosaurus like many other Dromaeosauriden wore an enlarged sickle- claw on the second (inner) toe. The phalanges (phalanges ) of the second toe, however, were more robust than that of Deinonychus, Velociraptor and Saurornitholestes, and were similar to those of the related genus Adasaurus. However Adasaurus only had a reduced sickle claw, which was no bigger than the claws of the other toes; this could indicate that also Dromaeosaurus had no enlarged sickle claw.

Nutrition

A biomechanical study of François Therrien and colleagues ( 2005) found that Dromaeosaurus a stronger bite force than had other Dromaeosauriden. So the bite of Dromaeosaurus was stronger than that of Deinonychus and even three times as strong as Velociraptor. Therrien and colleagues conclude from their results that Dromaeosaurus and perhaps other Dromaeosaurinen another hunting behavior than did the schmalschnäuzigen Velociraptorinen: So Dromaeosaurus could have wounded his prey with powerful bite while Velociraptorinen could have left more on their sickle claws. The jaw of Dromaeosaurus was not suitable, according to the researchers to retain strong prey.

History of Research

The first remains found the distinguished paleontologist Barnum Brown in 1914 near the Red Deer River in Alberta, Canada, during an expedition of the American Museum of Natural History. Today the locality as Little Sandhill Creek is known and is within the Dinosaur Provincial Park. These rocks date from the Campanian and belong to the Dinosaur Park Formation. The Fund ( 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, provide Brown and William Diller Matthew (1922 ) in a preliminary publication of the new genus with the type species Dromaeosaurus Dromaeosaurus albertensis on. Since the skull was incomplete and not fully prepared, they announced a more extensive description, which should appear in a later article. Matthew and Brown arranged Dromaeosaurus together with Gorgosaurus, Albertosaurus and Tyrannosaurus Deinodontidae the family (now Tyrannosauridae ) to. Nevertheless, they considered the differences to other Deinodontiden for large enough to be classified within the Dromaeosaurus Deinodontidae in its own subfamily, the Dromaeosaurinae. The name Dromaeosaurus means as much as " rennende lizard" ( Gr.: δρομεύς / Dromeus = " running ", σαῦρος / sauros = " lizard" ) and is intended to indicate an animal that unlike other Deinodontiden was small and slightly built.

A complete description of the findings was published by Colbert and Russell until 1969. Meanwhile, the skull was prepared for exhibitions, with missing elements were complemented by colored plaster and glue, what the description difficult - so covered the modeled elements anatomical details; sometimes the reconstruction was so very good that it was difficult to distinguish real from artificial elements. Later, after the description of Colbert and Russell, the skull was damaged. The mainly composed of elements modeled skull roof was thereby separated from the rest of the skull, the fragment of the parietal bone ( parietal ) went missing. But also features exposed by the damage that were not visible before. After another preparation, in which almost all modeled elements and remaining rock matrix was removed, Philip Currie published in 1995 a further, supplementary description, partly based on a computed tomography scan of the skull.

In addition to the holotype skeleton only a few fragmentary bones are known. Finds from the Judith River Group of Alberta and Montana include an isolated Frontale ( copy number NMC 12349 ), a fragmentary dentary and 30 isolated teeth with a. Some teeth from the Dinosaur Park Formation described Cope (1876 ) as originally Laelaps explanatus included possibly however Dromaeosaurus and sometimes as a separate species, Dromaeosaurus explanatus led. A phalanx, a claw and various isolated dentary were once attributed Dromaeosaurus, but actually belonged langstoni to the related Saurornitholestes. A partial metatarsal from the Laramie Formation of Colorado was originally described as Ornithomimus minutus described ( Marsh, 1892), but then by Russell (1972 ) as a further possible type of Dromaeosaurus, Dromaeosaurus minutus. Today, these species will be taken as a noun dubium ( a dubious name). Other remnants that could possibly belong to Dromaeosaurus come from the Prince Creek Formation of Alaska and are about 66 million years old ( Maastrichtian ).