An Ultimate Guide to the Utahraptor: Utah’s Robber

Leave a comment / / Updated on: 24th September 2023

Name MeaningUtah’s robberHeight1.5 meters (4.9 feet)
PronunciationYou-tah-wrap-toreLength4.9-7 meters (16-23 feet)
EraMesozoicEarly CretaceousWeight280-300 kilograms (617-661 pounds)
ClassificationDinosauria, Saurischia, & TheropodaLocationUtah, North America

Utahraptor Pictures

3D rendition of a Utahraptor
3D rendition of a Utahraptor | SEBASTIAN KAULITZKI via GettyImages

The Utahraptor

Gage Beasley Prehistoric's Utahraptor Concept
Gage Beasley Prehistoric’s Utahraptor Concept

The Utahraptor is widely recognized as one of the largest and heaviest dromaeosaurids.

Having been discovered in 1975, the Utahraptor roamed our planet 135-130 million years ago during the Early Cretaceous. 

It lived on North American territory. 

More precisely, it was a resident of today’s Utah and is now its state dinosaur.

Utah’s robber was a heavily built bipedal theropod. 

Although not too fast, it was a ferocious predator that likely relied on an ambushing predation technique. 

Additionally, it possessed sickle claws on its feet used to dispatch prey.

Keep reading to discover more jaw-dropping details about the deadly Utahraptor!

Gage Beasley's Prehistoric Shirt Collection
Gage Beasley’s Prehistoric Shirt Collection
Gage Beasley's Prehistoric Plush Collection
Gage Beasley’s Prehistoric Plush Collection

Physical Characteristics

Cast of the foot bones for Utahraptor showcasing its "sickle" claw
Cast of the foot bones for Utahraptor showcasing its “sickle” claw | Ghedoghedo via Wikipedia CC BY-SA 3.0

The Utahraptor is one of the largest and heaviest known dromaeosaurids. 

Naturally, further paleontological discoveries may disapprove of this statement, but until then, it remains the truth.

Although smaller than other dinosaurs, the Utahraptor was unusually large for its kind, measuring approximately 4.9-7 meters (16-23 feet) long.

Like in the case of many other dinosaurs, there’s a huge gap between estimations because they’re typically done based on different specimens.

One calculation argued it was roughly 11 meters (36 feet) long, but some scientists rushed to confirm this was an overestimation. 

Some argue that the closest to the truth is 5.5 meters (18 feet) long.

The same goes for the weight. 

While some suggest an average weight of 280-300 kilograms (617-661 pounds), others argue in favor of 500 kilograms (1,102 pounds).

Either way, other members of the Dromaeosauridae family were much smaller. 

The Daurlong, for example, was only 1.5 meters (4.9 feet) long. 

The Pamparaptor was even smaller, at most 0.5-0.7 meters (1.6-2.3 feet) long.

The Achillobator had roughly the same length, although lighter than the Utahraptor. 

It measured 3.9-5 meters (12.8-16.4 feet) long and weighed 165-250 kilograms (364-551 pounds).

The same is valid for the Dakotaraptor, which was 4.3-6 meters (14.1-19.7 feet) long and weighed 220-350 kilograms (485-772 pounds). 

Despite its large size, the Dakotaraptor is considered inferior to the Utahraptor in terms of proportions and adaptations.

Dromaeosaurines, including the Utahraptor, had a heavy build, a stout, box-shaped skull, and thick and heavy legs, which served more for strength than speed. 

Their teeth were fully serrated.

The Utahraptor had claws on its hands that functioned as cutting blades. 

It also had a large, curved claw on each foot. It grew from the second toe and could have likely reached a length of 24 centimeters (9.5 inches). 

Utahraptor has claws typical of its clade
Utahraptor has claws typical of its clade | EatThatPie via The Isle Wiki

The long tail may have served as a stabilizer or counterweight. 

Although it is generally believed that all dromaeosaurids had feathers, no fossil evidence confirms them in the Utahraptor

However, since more primitive dromaeosaurids are thought to have possessed feathers, we cannot rule out this possibility when discussing the Utahraptor

Habitat and Distribution

Utahraptor fossils were discovered in Utah. 

More precisely, they were unearthed in the Dalton Wells Quarry near Moab. 

Other remains were found in Gaston Quarry, Grand County. 

In paleontological terms, the Utahraptor was discovered in the Cedar Mountain Formation in eastern Utah, United States. 

This formation consists of sediments deposited on flood plains, lakes, and rivers.

The Cedar Mountain Formation comprises several members, and Utahraptor fossils were unearthed from the Yellow Cat and Poison Strip members.

The Yellow Cat Member is north of Arches National Park and consists of mudstones and sandstones deposited on flood plains. 

It is believed to have had arid to semi-arid conditions.

The Poison Strip member consists of sandstones deposited in river channels and limestones and mudstones deposited on flood plains. 

As such, scientists argue that this territory featured a river system.

The Cedar Mountain Formation likely served as a home for riverine forests and open woodlands where ferns, hornworts, and conifers grew. 

There may have been seasonal weather changes between the dry and wet seasons, although the latter was quite short. 

A Utahraptor during the early Cretaceous in what is now known as Utah
A Utahraptor during the early Cretaceous in what is now known as Utah | Orla via iStock

Wildfires were likely common during the dry season. 

The Utahraptor lived during the Valanginian and Hauterivian ages of the Early Cretaceous. 

While the world registered a cooling trend that started at the end of the Jurassic and continued into the first age of the Cretaceous, it started to warm up during the Valanginian, so the Utahraptor lived in a warm environment.

Behavior and Diet

The Utahraptor was a bipedal theropod. 

A Utahraptor moved by standing on its hind legs
A Utahraptor moved by standing on its hind legs | Emily Willoughby via Wikipedia CC BY-SA 3.0

It was a carnivore and quite a good predator, especially thanks to its legs and pedal sickle claws.

Although it wasn’t as fast as other dromaeosaurids and carnivorous theropods, it had a strong leg force used to subdue and kill prey.

Supposedly, because it lacked the speed of the Velociraptor, for example, the Utahraptor was likely an ambush hunter. 

Once it reached its prey, the Utahraptor may have maintained its balance better than other raptors.

The manual unguals were of help as well, especially since they were much thinner than in other clawed dinosaurs and, thus, much sharper.

These traits allowed the Utahraptor to ambush, subdue, and kill much larger prey, measuring as much as 8 meters (26.3 feet) in length and weighing as much as 1,000-2,000 kilograms (2,205-4,409 pounds). 

Furthermore, some scientists believe that the Utahraptor may have hunted in packs. 

A pack of Utahraptors securing their kill
A pack of Utahraptors securing their kill | LuqBot via The Isle Wiki

They concluded this upon discovering seven individuals in the same spot.

If this assumption is true, it would further enhance these dinosaurs’ chances of feeding on large prey, sometimes killing sauropods as large as 20 meters (65.6 feet) long! 

However, this hunting behavior hasn’t been fully approved by scientists.

The discovery mentioned above may also represent one of the most well-preserved predator traps, as the remains belonged to an adult, four juveniles, a hatchling, and at least one iguanodont.

The Utahraptor was a major carnivore in its habitat and filled an important ecological role precisely due to its unique ability to catch and kill much larger prey.

Life Cycle

Like all dinosaurs and modern birds, the Utahraptor reproduced by laying eggs. 

Beyond that, little is known about this dromaeosaurid’s reproductive behavior. 

Studies have been conducted on dinosaurs in general, but few focus on particular species, so it would be speculation to suggest any nesting or incubating behavior for the Utahraptor.

A pair of Utahraptors
A pair of Utahraptors | Kurt Miller via GettyImages

A fossilized egg has been associated with the Deinonychus, a close relative of the Utahraptor. 

It has been suggested that the egg was similar to oviraptorid eggs and was an indicator of brooding, meaning that these dinosaurs incubated their eggs.

It has also been suggested that Deinonychus laid blue eggs. 

This may represent the origin of the colored eggs we observe in modern birds. 

Are these details valid for the Utahraptor, too? This will remain a mystery until future paleontological discoveries and studies shed light on these aspects.

Since Utahraptor juveniles and adults were found in the same place, it has been argued that they may have exhibited social or group behavior. 

However, some studies suggest that dromaeosaurid juveniles and adults had different dietary preferences, making the hunting theory and the complex social structures implausible.

Another theory says they may have cooperated only for a short period to catch prey and then parted ways until another hunting possibility appeared.

A pack of Utahraptor in search of prey
A pack of Utahraptor in search of prey | Kostyantyn Ivanyshen via GettyImages

Evolution and History

The relationship between dromaeosaurids and birds has been long debated. 

Some scholars even argued that dromaeosaurids should be classified as birds since they share many traits. 

Naturally, other scientists rushed to disagree with this statement.

At first, the Microraptor was considered the most primitive dromaeosaurid. 

In 2007, however, scientists described the Mahakala, which is now widely regarded as the most basal and primitive member of this family. 

This is an indicator that the dromaeosaurid ancestors were flightless.

Dromaeosaurids such as Utahraptors are considered flightless proto-birds
Dromaeosaurids such as Utahraptors are considered flightless proto-birds | Nobumichi Tamura via GettyImages

On the other hand, other studies indicate that the Xiaotingia, a dromaeosaurid similar to the Archaeopteryx, should be named the most primitive member of the Dromaeosauridae family. 

If this is true, it would mean that the most primitive dromaeosaurids could fly.

Either way, it is widely accepted that the Utahraptor is a dromaeosaurid classified in the Dromaeosaurinae subfamily under the Eudromaeosauria clade.

The first Utahraptor fossils were discovered in 1975. 

However, the type species (and the only one in the genus), Utahraptor otrommaysi, was named only in 1993. 

Unlike its classification, the specific name has undergone some changes over the years. This is why you may stumble upon alternative spellings in scientific literature, including ostromaysorum, ostromayorum, and ostrommaysori.

Upon its classification and description, the Utahraptor was confirmed to be a close relative of the Dromaeosaurus, Achillobator, and Dakotaraptor.

Size of Utahraptor compared with other dromaeosaurs
Size of Utahraptor (5) compared with other dromaeosaurs | Fred Wierum via Wikipedia CC BY-SA 4.0

Before the discovery of the Utahraptor, scientists believed that all dromaeosaurids possessing a sickle claw were small creatures of the Late Cretaceous. 

As such, Utahraptor fossils were evidence of the existence of larger forms during the Early Cretaceous.

Interactions with Other Species

The Cedar Mountain Formation is regarded as one of the richest fossil locations in the United States. 

Considering this, we may safely assume that many other bizarre prehistoric creatures surrounded the Utahraptor!

Since it was a ferocious predator, often considered one of the strongest dinosaurs, it was likely feared by most herbivores, even the largest ones!

A pair of Utahraptors planning to take down a pair of sauropods
A pair of Utahraptors planning to take down a pair of sauropods | Kostyantyn Ivanyshen via GettyImages

Since the formation revealed numerous fossils, it would be quite challenging to confirm which ones interacted with the Utahraptor – that is, besides the ones Utah’s robber preyed upon.

Nevertheless, here’s a list of the creatures discovered in the Cedar Mountain Formation that the Utahraptor may have stumbled upon during its 5 million years of existence on Earth:

  • Ankylosaurs like Gastonia
  • Iguanodontians like Cedrorestes, Hippodraco, and Iguanacolossus
  • Sauropods like Cedarosaurus, Moabosaurus, and Mierasaurus
  • Theropods like Falcarius, Germiniraptor, Martharaptor, Nedcolbertia, and Yurgovuchia
  • Amphibians like salamanders and frogs
  • Aquatic turtles
  • Snakes
  • Lizards
  • Birds
  • Mammals like Cifelliodon

The Utahraptor is thought to have preyed on larger iguanodontians and sauropods and probably didn’t even consider taking smaller animals as prey. 

Cultural Significance

Utahraptor skeleton BYU's Museum of Paleontology
Utahraptor skeleton BYU’s Museum of Paleontology | Jaren Wilkey via Wikipedia CC BY-SA 4.0

The most important thing to mention when discussing the cultural significance of the Utahraptor is that this creature has been named the Utah state dinosaur.

Additionally, a state park in Grand County, Utah, has been named after the Utahraptor

It is located approximately 23 kilometers (14 miles) northwest of Moab. 

The large block containing several Utahraptor specimens was excavated there.

Robert T. Bakker, an American paleontologist, wrote one famous novel. 

It is called Raptor Red. It tells the story of Cretaceous dinosaurs and is written from the perspective of a female Utahraptor.

This is one of the most important attempts to make the Utahraptor known to dinosaur enthusiasts. 

Over the years, many aspects discussed in the book were confirmed to be inaccurate, but we must still acknowledge its impact on the public.

This novel was followed by multiple media representations that enhanced the Utahraptor’s popularity among dinosaur enthusiasts. 

It is now renowned as one of the strongest known dinosaurs and is often portrayed as a ferocious, feathered predator.

Raptors such as Utahraptors are often portrayed as a feathered hunter
Raptors such as Utahraptors are often portrayed as a feathered hunter | DinoSteve93 via Theropods Wiki

The portrayal of raptors in the Jurassic Park universe is incredibly significant. 

The producers had created the raptors before the Utahraptor was described. Upon its description, they realized the fictional creature was much like the real one!


Often regarded as one of the strongest dinosaurs ever discovered, the Utahraptor went on daily walks in a territory we now call Utah.

Although we naturally cannot confirm it was among the strongest, as this would be pure speculation, we can argue that the Utahraptor truly was a ferocious creature capable of subduing and killing much larger prey!

Its most distinctive characteristics are the sickle claws found on each foot. 

Apart from this, the Utahraptor is known to be quite large for a dromaeosaurid. 

On the other hand, it wasn’t very fast and likely relied on ambushing predation rather than pursuit predation.


What is the difference between a Velociraptor and a Utahraptor?

The Velociraptor and the Utahraptor are both eudromaeosaurian dromaeosaurid theropods. 

The Velociraptor is classified in the Velociraptorinae subfamily. 

In contrast, the Utahraptor is classified in the Dromaeosaurinae subfamily. 

This makes them different dinosaurs, despite sharing a similar body build and physical characteristics.

Two things that can help you distinguish them are the size (the Velociraptor was smaller) and the snout form (the Velociraptor had a narrower snout). 

Additionally, the leg form was different in the Velociraptor, thus allowing it to attain higher speeds.

When did the Utahraptor go extinct?

The Utahraptor went extinct 130 million years ago, during the Hauterivian age of the Early Cretaceous. 


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