Skeletal reconstruction of Utahraptor ostrommaysorum

  • Utah, USA ( Cedar Mountain Formation)
  • Utahraptor ostrommaysorum

Utahraptor is a genus of carnivorous dinosaur from the group of Dromaeosauridae. Utahraptor is known only by very fragmentary remains, which were discovered in eastern Utah (USA) and in the Lower Cretaceous ( Barremian ) be dated.

With a length of approximately 7 meters Utahraptor is the largest known Dromaeosauride. This genus was described scientifically by James Ian Kirkland, Robert Gaston, and Donald Burge 1993, the only way is Utahraptor ostrommaysorum. Because of its size Utahraptor is one of the most commonly -received in popular representations Dromaeosauriden.


Utahraptor is estimated by Kirkland and colleagues to a length of about 7 meters and a weight of 500 kg. A similar size reached under the Dromaeosauriden only Achillobator from the Upper Cretaceous of Mongolia, which is estimated at a length of about 5 meters. Most commonly claws are in the fossil record. Like other Dromaeosauriden Utahraptor showed an enlarged sickle- claw on the inner toe. This is narrated by a 22 cm-long fossil; reconstructs it was probably 24 inches long. Kirkland and colleagues described putative hand claws that are great and significantly thinner than any other Dromaeosauriden why they would have been better suited as weapons for cutting. Later it turned out that it was indeed Fußkrallen these claws.

From the skull the premaxillary bone ( premaxilla ) is known. Kirkland and colleagues described a lacrimal bone ( lacrimal ), this turned out later, however, than the postorbital of Nodosauriers Gastonia. The paired premaxillary bone, a tooth- bearing bone, which lies in front of the upper jaw (maxilla ), carries four teeth on each side, as with other Dromaeosauriden. Only two teeth are preserved for the most part: The first tooth is 31 mm, the second in 45 mm length obtained. For most other Dromaeosauriden the denticles ( tooth ) on the front cutting edge of the teeth is much smaller and more numerous than in the rear; at Utahraptor but this difference is only slight. The denticles are unlike other Dromaeosauriden simple and blunt; similar denticles are found only in Dromaeosaurus. The denticles of Dromaeosaurus but are proportionally larger. There are known three caudal vertebrae. The vertebral bodies were platycoel, so on one end flat, on the other convex. The vortices show that the tail was reinforced by rods -like spinous processes, as with most other Dromaeosauriden (prolonged post and prezygapophyses and Chevronknochen ). The tibia is straight and solid, indicating a strong leg. Kirtland and colleagues speculate that this adjustment was used to constituted the sickle claw as possible powerful.


Today Utahraptor is considered closely related to Achillobator and Dromaeosaurus, together they form a distinct group within the genus Dromaeosauridae that Dromaeosaurinae. Already Kirtland and colleagues suspected on the basis of similarities in the shape of the denticles that Utahraptor is more likely attributable to the Dromaeosaurinae than the Velociraptorinae.

Function of the hands and feet and speed

Kirtland and colleagues speculated that Utahraptor, if he lived in packs, very large prey such as up to 20 meters long could kill sauropods. They followed it to the then widespread view Dromaeosauriden had jumped to large prey, clung with their long arms and slit open the belly of the prey with its sickle claw. They speculated that Utahraptor could have stabbed prey due to its sheer size, with its sickle claw, without running the risk of losing by the force of this attack balance. Unlike smaller Dromaeosauriden he could thus have his hand claws used not only to retain but also to wound the prey. Then the thinner hand claws would indicate that were better adapted to a cutting than the other claws Dromaeosauriden. The hand claws have at Utahraptor thus to kill the prey can play an almost equally important role as the sickle claw. Later, however, showed that the supposed hand claws were actually Fußkrallen.

Recent research by Manning and colleagues ( 2005) using a mechanical robot model of the foot of Deinonychus have shown that the sickle claw of Dromaeosauriden can not be used for slitting. Instead, it was ideal for hard claws on prey. Injuries were inflicted primarily according to these researchers by the hand claws and teeth. The sickle claw may have served to selectively pierce carotid artery and trachea, as suggested in the famous fossil of a Velociraptor fighting.

Compare with deinonychus suggest that the tibia was proportionally shorter than the latter, and in that the femur and tibia were about the same length. This corresponds to the proportions, as found in other large theropods. The researchers conclude that Utahraptor proportional could not run as fast as Deinonychus or Velociraptor. But is at least as fast as the Iguanodontiden been that could have belonged to his prey Utahraptor.

Finds, history of discovery and naming

The fossils come from two quarries which are located about 40 kilometers away from each other in eastern Utah near Arches National Park. The sedimentary rocks, from the date the fossils belong stratigraphically to the Cedar Mountain Formation, an important fossil site of the Lower Cretaceous.

The first Utahraptor fossils were ausgebraben in the summer of 1975 by Jim Jensen and his group in Dalton -well Quarry and Museum in Provo ( Utah) have since been in the Brigham Young Earth Science stored. The Dalton -well - hid Quarry total of hundreds of relatively well-preserved bones. Since the bones were transported prior to embedding, it is a conglomeration of individual bones of different individuals. In the bones, the Utahraptor were later attributed, are two Fußkrallen (BYU 13068 and BYU 9438, originally as a hand claws identified ), a middle caudal vertebra (BYU 9435 ) and two rear (distal) and caudal vertebrae (BYU 9435 and 9436 ).

More Utahraptor - bones were found in the Gaston Quarry in October 1991 during the excavation of a Nodosaurier skeleton. In this quarry, a total of 300 bones were discovered in the summers of 1991 and 1992. These excavations were led by Kirkland and Burge and were part of a joint project of Dinamation International Society and the College of Eastern Utah Prehistoric Museum. In the latter, the fossils are preserved. The age of the sediments of this discovery site has been radiometrically dated at 126 million years (Upper Barremian, Lower Cretaceous ). Utahraptor fossils of this discovery site include the holotype specimen ( specimen number 184v.86 CEU ) with a, is the sickle claw of the right foot. Furthermore, a claw ( CEU 184v.294 ), a shinbone ( tibia, 184v.260 CEU ), a lacrimal bone ( lacrimal, 184v.83 CEU ) and an intermediate jaw bone ( premaxilla, CEU 184v.400 ) were found.

In 1993, the new genus and species of Kirkland, Gaston and Burge was scientifically described. The name Utahraptor is composed of the locality, the U.S. state of Utah, and raptor together, which comes from Latin and means " robber " means. The species name honors John ostrommaysorum Ostrom and Chris Mays. John Ostrom was an eminent paleontologist who has rendered outstanding especially with the study of Deinonychus. Chris Mays is the founder of the International Society Dinamation, which nudged the research and was involved in its funding. Originally it was planned that way Utahraptor to name spielbergi, in honor of Steven Spielberg, the director of the very successful dinosaur adventure film Jurassic Park. However, Spielberg's lawyers objected. In the first description the species is referred to as Utahraptor ostrommaysi. The International Rules for Zoological Nomenclature ( ICZN ) require, however, that the correct Latin genitive plural ending - orum must be used, since ostrommaysi refers to more than one person.

In popular culture

Utahraptor appears in a variety of popular presentations about dinosaurs. Thus, the novel Raptor Red (1995 ) is written the paleontologist Robert Bakker from the perspective of a female Utahraptor. Utahraptor appeared in the BBC documentary film dinosaur - on In the Realm of the Giants ( Walking with Dinosaurs ). Another example is the amendment Raptor by Paul Zindel. In most of these representations Utahraptor appears without springs. In fact, never feathers were found in association with Utahraptor fossils. Nevertheless, the detection of feathers speaks in a variety of other Dromaeosauriden that all members of the group were feathered including Utahraptor (principle of phylogenetic grip ).