Utahraptor

*Utahraptor oweni*

***Utahraptor*** (meaning "Utah plunderer") is an extinct genus of carnivorous dromaeosaurid from the Barremian stage of the Early Cretaceous, living in what is now North America. Related to *Deinonychus* and *Velociraptor*, *Utahraptor* is the largest dromaeosaur known to science. *Utahraptor* is also a member of the Dromaeosaurinae, a group of dromaeosaurids that relied heavily on their jaws to kill their prey. Utahraptor was closely related to *Dromaeosaurus*, *Achillobator*, and *Dakotaraptor* among others based on cladistic analysis.

In 2018, it was proposed that Utahraptor be the Utah state dinosaur, an act that was approved by the Senate. Initially *Utahraptor* would have replaced another dinosaur, *Allosaurus*, as the state's official fossil, but it was decided that *Utahraptor* would be another symbol of the state.

## Discovery and naming

The first specimens of Utahraptor were found in 1975 by Jim Jensen in the Dalton Wells Quarry in east-central Utah, near the town of Moab, but did not receive much attention. The species name o*strommaysi* was named after John Ostrom, who contributed of the bird-like characteristics of *Deinonychus*. And also Chris Mays, the head of the Californian animatronic company Dinamation who funded the expedition of *Utahraptor*.

James Kirkland, Rob Gaston, and Don Burge discovered *Utahraptor* in 1991 in Grand County, Utah, within the Cedar Mountain Formation. The type specimen is currently housed at the College of Eastern Utah Prehistoric Museum, although Brigham Young University currently houses the largest collection of *Utahraptor* fossils.

The type species (and only known species of *Utahraptor*), *Utahraptor ostrommaysi*, was named for the American paleontologist John Ostrom, from Yale University's Peabody Museum of Natural History, and Chris Mays, of Dinamation International. Sculptor Raymond Persinger was included in James Kirkland's original abstract referencing Mr. Persinger's concepts regarding the claw structure.

## Description

The holotype of *Utahraptor* is fragmentary, consisting of skull fragments, a tibia, claws and some caudal (tail) vertebra. The few elements suggest an animal about twice the size of *Deinonychus*. Like other dromaeosaurids, *Utahraptor* had a huge curved claw on the second toe, one is preserved at 22 centimeters (8.7 in) in length and is thought to reach 24 centimeters (9.4 in) restored. Up to 6.5 m (21 ft) long, 2 m (6.6 ft) tall, and 700 kg (1,500 lb) in weight, *Utahraptor* would have been a formidable predator.

It is thought that *Utahraptor* may be closely related to the much smaller *Dromaeosaurus* and the giant Mongolian dromaeosaurid *Achillobator*.

## Classification

Utahraptor is a member of the family Dromaeosauridae, a clade of theropod dinosaurs commonly known as "raptors".

## Physical Appearance

*Utahraptor* was a very large dromaeosaur, one of the biggest members of its' family. It was about 1.7-2 meters tall, 6-7 meters long, and weighed about 1,000 pounds/453 kg. It lived from 131 to 126 mya during the Barremian Stage of the early Cretaceous and is closely related to *Achillobator* and *Dromaeosaurus*. Its skeletal design was birdlike; with bones that were hollow, but strong. Recent fossil discoveries of more complete skeletons of Utahraptor by James Kirkland et al. paint a picture also of a dromaeosaur that was more heavily-built and stocky than the "typical" *Deinonychus* body plan generally associated with other dromaeosaurs. The legs were short and stocky, while the tail was also relatively short in comparison to that of related forms. The jaws were most unusual, with the front of the lower jaw bent forward and down in a case of convergence with the unrelated Masiakasaurus.

*Utahraptor* and other dromaeosaurs might have had binocular vision, like that of an eagle. Its hearing was probably excellent. Scientists recently discovered that raptors in general could best hear low frequency sounds. Dromaeosaurs like *Utahraptor*, regardless of size, were all covered in feathers according to cladistic analysis. Though feathers from the arms were known to be true feathers in other dromaeosaurs such as Dakotaraptor and Velociraptor, the rest of the dinosaur's plumage is speculative (though fossil finds of smaller species exhibit many of the same types of feathers that are found in modern birds, In Utahraptor, the exact plumage type is not known).

The feathers on the arms of young dromaeosaurids would have enabled a special type of locomotion called wing-assisted incline running, or WAIR for short. Discovered by Ken Dial, a Montana zoologist, this is a behavior used by modern birds that combines flapping the wings back and forth while running up the sides of trees. This flapping pushes the feet of the bird against the tree, allowing it to run vertically up the trunk. This indicates, but does not prove, that small dromaeosaurs lived part-time in the trees. In larger species, the wing feathers may have helped to maintain balance while attacking prey.

## Diet

*Utahraptor’s* diet consisted predominantly of large herbivorous dinosaurs. In the formations where it was found (the Yellow Cat and Poison Strip members of the Cedar Mountain Formation, respectively), Utahraptor lived alongside such dinosaurs that it preys on such as *Gastonia*, *Iguanodon*, *Hippodraco*, *Cedrorestes*, *Iguanacolossus*, *Martharaptor*, and *Falcarius*. Sauropods such as *Venenosaurus* and *Cedarosaurus* were also on its menu and also found here, as were other predators that it live with such as *Nedcolbertia* and *Geminiraptor*. Any one of these was a potential prey item, though the smaller animals such as *Necolbertia* would have been little in the way of a meal for such a predator as *Utahraptor*. As with all predators, *Utahraptor* likely targeted animals such as the infirm, weak and inexperienced. Scavenging was also probably a preferable opportunity when there was access to a carcass. Like most dromaeosaurine dromaeosaurids, Utahraptor probably relied on its jaws to kill prey more than other subfamilies of dromaeosaurs did. As a result and based on the analysis of related species like *Dromaeosaurus*, which included bone in its diet, *Utahraptor* probably had an extremely powerful bite as a result.

## Speed and Agility

*Utahraptor* was likely an ambush predator. Given its robust, stocky build and short legs, it was not particularly fast, but given that its prey was likely slower, what it lacked in speed it made up for with power and agility.

## Habitat

*Utahraptor's* habitat was a series of floodplains and open woodlands with riverine forests. The wet season was short in this habitat and the climate was semi-arid. As *Utahraptor* was not fast, it likely used the available cover to lie and wait for prey.

## Paleobiology

### Hunting

Kirkland et al. note that, given how large it was, it would not have been as fast as *Deinonychus* or *Velociraptor*. Instead they assume a speed similar to contemporary iguanodonts and faster than sauropods. A thick tibia indicates a large leg force that could kill prey. It may have kicked forward with its legs, but was likely so heavy that it did not to use its arms as balance (like smaller forms would have needed to). This would have freed the hands for other uses, such as dispatching prey. G.S. Paul states that Utahraptor was not very fast and was likely adapted to ambush, preying on iguanodonts and therizinosaurs. It's large sickle claw was suited to hunting large prey. It likely relied on it's jaws while hunting, more so than other dromaeosaurids. Bruce Rothschild (2001) examined for stress fractures in referred specimens, finding none. This indicates an unexpected condition or behaviour. *Utahraptor* was important as a major predator and could attack much larger prey. If a pack consisting of 3.5 meter long and 70 kilograms heavy individuals existed, they could take on prey 8 meters long and 1-2 tonnes heavt. Sauropods about 20 meters long may have been a key element to their diets, if it was social.

### Social Behavior

In 2001, Kirkland et al, pursued a graduate student's discovery of a bone protruding from a 9-ton fossil block of sandstone in eastern Utah. It was determined to contain the bones of at least seven individuals, including an adult measuring about 4.8 meters, four juveniles and a hatchling about 1 meters long. Also fossilized with the predators are the remains of at least one possible iguanodont herbivore. Kirkland speculated that the *Utahraptor* pack attempted to scavenge carrion or attack helpless prey mired in quicksand, and were themselves mired in the attempt to attack the herbivore. Similar sites such as the Cleveland-Lloyd Quarry and California's La Brea Tar Pits house such predator traps. Examination of the fossils are ongoing after a decade of excavation, but if Kirkland is correct, it may be one of the best-preserved predator traps ever discovered. The fossils may further reveal aspects into the behavior of *Utahraptor*, such as whether it might have hunted in groups like Deinonychus was believed to have done. Whether all the *Utahraptor* individuals were mired simultaneously or were drawn in, one-by-one is unclear. Further examination of the block suggests that the number of *Utahraptor* remains maybe double the amount previously assumed.

While the social and complex behavior of the dromaesauridae can merely be theorized, it was later discovered in 2020 that Deinonychus may not have had complex social behavior seen in some pack-hunting animals in the modern era.

## JPInstitute.com Description

When the movie "Jurassic Park" was released, dinosaur fans everywhere complained that director Steven Spielberg had made his movie Velociraptors much larger than they were in real life. In the midst of this controversy, Dr. James Kirkland and paleontology student Rob Gaston unearthed the real-life giant raptor that was shown in the movie - only bigger! Utahraptor was huge, and with its big killing claws, strong arms and hands, and sharp teeth, it was one of the most ferocious killers on the planet.

One of the most unique aspects that Utahraptor shares with its more famous cousin Velociraptor is that both had a lethal killing claw on each foot. Each inside toe had a large (about 10 inches) hooked claw that was controlled by a strong tendon. This claw was held upward when the animal was walking or running. When it attacked, however, the tendon snapped tight and the claw clamped down with great speed and force, slicing deeply into its victim. Not a very pretty picture, but an effective way to inflict a serious wound.

Utahraptor is the oldest known, and largest, of the dromaeosaurids. This is interesting as it points to a family that shrunk over time. Its hand claws were proportionally larger than other family members and Dr. Kirkland speculates that its hand claws were probably as important a weapon as the killing claws on its feet. Utahraptor is the subject of a best-selling book by Dr. Robert Bakker. Entitled "Raptor Red," it is currently being developed into a motion picture.

## Appearance in other media

### *Jurassic Park*

* *Utahraptor* can be created in *Jurassic Park: Builder*. At first, it could only in the Jurassic card packs purchasable by real money. Since February 12th 2016, it became a DNA tournament limited edition. Unlike most dromaeosaurids in the Jurassic Park franchise, this depiction of *Utahraptor* has fur-like feathers all over its body and even wings, although it is shown inaccurately to be able to pronate its hands.

* *Utahraptor* can be created in *Jurassic World: The Game*. Unlike most dromaeosaurids in the Jurassic Park franchise, this depiction of *Utahraptor* has fur-like feathers all over its body and even wings, although it is shown inaccurately to be able to pronate it's hands in battle.

* *Utahraptor* will be *Jurassic World: Alive*. Unlike most dromaeosaurids in the Jurassic Park franchise, this depiction of *Utahraptor* has fur-like feathers all over its body and even wings, although it is shown inaccurately to be able to pronate it's hands.

## Links

http://web.archive.org/web/20040214160622fw\_/http://www.jpinstitute.com/dinopedia/dinocards/dc\_utahr.html
https://web.archive.org/web/20080706033204/http://kids.yahoo.com/dinosaurs/50--Utahraptor

## References

1. ↑ https://nhmu.utah.edu/utahraptor-ostrommaysorum
2. ↑ https://www.smithsonianmag.com/science-nature/utahraptor-largest-raptor-180974954/
3. ↑ https://www.academia.edu/225747
4. ↑ https://geology.utah.gov/popular/general-geology/dinosaurs-fossils/megablock/
5. ↑ 5.0 5.1 5.2 5.3 Kirkland, J.I., Burge, D., and Gaston, R. (1993). "A large dromaeosaur [Theropoda] from the Lower Cretaceous of Utah." *Hunteria*, **2**(10): 1-16.
6. ↑ Template:Cite journal
7. ↑ https://www.geol.umd.edu/~tholtz/dinoappendix/HoltzappendixWinter2011.pdf
8. ↑ https://press.princeton.edu/books/hardcover/9780691167664/the-princeton-field-guide-to-dinosaurs
9. ↑ https://www.semanticscholar.org/paper/Theropod-stress-fractures-and-tendon-avulsions-as-a-Rothschild-Tanke/5ae331f46c1a82ff0c8b7845faa9de3c9fcd4452
10. ↑ https://www.scienceopen.com/document?vid=3ae2eccb-a00b-4f69-b949-ca964c9e66cb