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.
Where fossils were found
Cedar Mountain Formation
Utah, Colorado · United States
137.1–132.6 million years ago(4.5m year span)
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Iguanodon
Iguanodon bernissartensis
Iguanodon was present in Early Cretaceous ecosystems contemporaneous with Utahraptor.
Acrocanthosaurus
Acrocanthosaurus atokensis
Both large theropods lived in Early Cretaceous North America with temporal overlap.
Deinonychus
Deinonychus antirrhopus
Both are large North American dromaeosaurids that evolved hypertrophied sickle claws for predation.
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
Microraptor gui
Both dromaeosaurids but representing opposite ends of the family's size spectrum and ecological experimentation.
Sauroposeidon
Sauroposeidon proteles
Sauroposeidon fossils are known from Early Cretaceous deposits in North America (Antlers Formation) that overlap temporally with Utahraptor's Cedar Mountain Formation.