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DVL-0143Specimen Record

Utahraptor

Utahraptor ostrommaysorum

YOO-tah-RAP-tor OS-trom-may-SOR-um

AI Reconstruction of Utahraptor ostrommaysorum, generated in 2026
  • Giant Sickle Claw: The curved claw on the second toe measured up to 24 cm — about as long as a large kitchen knife — making it the biggest "killing claw" of any raptor dinosaur ever found. CT scans show this claw was held off the ground while walking and snapped down to pin or stab prey, working more like a climber's spike than a slashing blade.
  • Beefy Arms: Forget the skinny arms of Velociraptor — Utahraptor had thick, powerful forelimbs with deep grooves in the bone where huge muscles attached. These burly arms could grapple and hold down big prey like the armored dinosaur Gastonia, giving this predator a noticeably bulky shoulder and upper arm compared to its smaller cousins.
  • Stiff Rod Tail: The tail was stiffened along most of its length by long bony rods that interlocked around the spine like a bundle of chopsticks. This turned the tail into a built-in balancing pole — super important when a 300 kg predator needed to twist and turn while wrestling dangerous prey.
  • Likely Feathered: No fossilized feathers have been found yet, but close relatives like Microraptor and Zhenyuanlong were definitely feathered — so Utahraptor almost certainly had plumage too, especially on its arms and tail. At this dinosaur's hefty size, a full fluffy coat wasn't needed for warmth, but feathers might have stuck around for showing off.
  • Deep Powerful Skull: Skull fragments reveal a head that was deeper and more heavily built than smaller raptors like Velociraptor and Deinonychus, which had longer, flatter snouts. That chunky skull could deliver a much stronger bite — perfect for taking down the large prey that shared its Early Cretaceous world.
●Early Cretaceous145–100.5 mya🥩 Carnivore🦵 Biped

Utahraptor was the largest known dromaeosaurid, a heavily-built raptor dinosaur from Early Cretaceous Utah. Famous for its enormous sickle-shaped toe claws measuring up to 24 cm, it was a formidable apex predator that likely hunted large prey.

Did you know?
  • Utahraptor's sickle claw measured up to 24 cm (9.4 inches) along the outer curve — the largest of any known dromaeosaurid

About

Utahraptor ostrommaysorum was a massive , far exceeding its famous cousin Velociraptor in size. Its most distinctive feature was the enlarged, curved claw on the second toe of each foot, which could reach 24 centimeters along the outer curve. Unlike smaller, gracile dromaeosaurids, Utahraptor had a robust, heavily-muscled build suggesting it was adapted for tackling large prey rather than speed. The animal lived in a semi-arid floodplain environment alongside other dinosaurs like Gastonia and various sauropods. Discovery of a mass death assemblage known as the 'Utahraptor megablock' suggests these predators may have hunted cooperatively or at least congregated around prey. Utahraptor represents crucial evidence that giant dromaeosaurids existed earlier in the Cretaceous than previously thought.

Quick Facts

Scientific name
Utahraptor ostrommaysorum
Group
Theropod · Dromaeosauridae
Lived
Early Cretaceous, 137.1–132.6 million years ago
Diet
Carnivore
Movement
Walked on two legs
Fossils found in
Cedar Mountain Formation (Utah, Colorado, United States)
Discovery credited to
1991, James Kirkland, Robert Gaston, and Donald Burge
Holotype
CEU 184v.86, College of Eastern Utah Prehistoric Museum
DinoVault record
DVL-0143

Where fossils were found

Cedar Mountain Formation prehistoric landscape

Cedar Mountain Formation

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Modern location

Utah, Colorado · United States

When it lived

137.1–132.6 million years ago(4.5m year span)

Where Utahraptor Roamed

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During the Early Cretaceous, Utahraptor roamed the floodplains and river channels of what is now eastern Utah, a semi-arid landscape dotted with seasonal lakes and bordered by ancient highlands, long before the Western Interior Seaway would divide North America. This dynamic environment, preserved in the Cedar Mountain Formation, supported a diverse ecosystem of ferns, conifers, and early flowering plants beneath a warm, seasonally dry climate.

Keep exploring the vault

Gastonia
🥩 Prey

Gastonia

Gastonia burgei

Utahraptor and Gastonia are both known from the Cedar Mountain Formation's Yellow Cat Member, representing the apex predator and a heavily-armored herbivore of the same ecosystem.

Iguanodon
🥩 Prey

Iguanodon

Iguanodon bernissartensis

Iguanodon was present in Early Cretaceous ecosystems contemporaneous with Utahraptor.

Acrocanthosaurus
⚔️ Rival

Acrocanthosaurus

Acrocanthosaurus atokensis

Both large theropods lived in Early Cretaceous North America with temporal overlap.

Deinonychus
🔀 Evolutionary echo

Deinonychus

Deinonychus antirrhopus

Both are large North American dromaeosaurids that evolved hypertrophied sickle claws for predation.

Velociraptor
🔀 Evolutionary echo

Velociraptor

Velociraptor mongoliensis

Fellow dromaeosaurid exploring the same predatory adaptations — enlarged sickle claw, stiffened tail for balance, and likely feathered body plan — but in a smaller-bodied Asian lineage.

Microraptor
🔀 Evolutionary echo

Microraptor

Microraptor gui

Both dromaeosaurids but representing opposite ends of the family's size spectrum and ecological experimentation.

Sources & Citation

Cite this record

Records are updated as research changes, so citations include the date you accessed this page.

Length estimates
Kirkland et al. 1993; Turner et al. 2012
Height estimates
Estimated from skeletal proportions; Kirkland et al. 1993
Weight estimates
Kirkland et al. 1993; mass estimates vary based on body reconstruction methodology
Speed estimates
Biomechanical estimates based on limb proportions; robustness suggests lower speed than smaller dromaeosaurids