Dinosaurs A to Z
Dromaeosauridae

Utahraptor ostrommaysi YOO-tah-RAP-tor

"Utah's thief"

Utahraptor silhouette
You 1.8 m (5.9 ft) tall
Utahraptor 6 m (19.7 ft) long
as long as 4 people standing fingertip to fingertip
silhouette · Becky Barnes (CC0) via PhyloPic
Length
6 m (19.7 ft) — About 6 m long, ~500 kg — the largest dromaeosaur ever found.
Period
Early Cretaceous (126–124 Mya)
Place
North America · Utah
Food
Carnivore — Large prey — iguanodontians, juvenile sauropods, anything it could pin down.
Clade
Dromaeosauridae Dinosauria Saurischia Theropoda Coelurosauria Sickle-clawed raptors: Velociraptor, Deinonychus, Utahraptor.

The largest known raptor, a stocky Early Cretaceous hunter built like a polar bear.

Utahraptor was the giant of the dromaeosaur family — about the size of a polar bear and built like a bird of prey scaled up to bear weight. Its discovery in 1991, right when Jurassic Park was in production, changed how filmmakers imagined raptors. A massive sandstone block found in Utah preserves at least six Utahraptors that may have been mired together in quicksand.

More about Utahraptor

Discovery

Named by James Kirkland, Robert Gaston, and Donald Burge · 1993 · the Gaston Quarry in Grand County, Utah, within the Yellow Cat and Poison Strip members of the Cedar Mountain Formation

The first specimens were found in 1975 by Jim Jensen but drew little attention. After Carl Limone found a large claw in October 1991, Kirkland, Gaston, and Burge uncovered further remains the same year, and the type species was named in June 1993.

The genus name means "Utah's predator," referring to the U.S. state of Utah where it was found. The text notes a wrinkle: the Latin word raptor actually translates to "robber" or "plunderer," not "predator."

James Kirkland. An American paleontologist who, with colleagues, described and named Utahraptor in 1993.

Was Utahraptor feathered?
The text says Utahraptor was likely feathered, based on evidence of filamentation in other dromaeosaurs. No direct feather impressions are reported for Utahraptor itself, so this is an inference from its close relatives rather than a confirmed find.
For the curious → Where does Utahraptor sit on the raptor family tree?
Kirkland originally placed it in the subfamily Dromaeosaurinae, now part of cladeA branch of the tree of life: an ancestor and all of its descendants. Eudromaeosauria, and most analyses keep it near there. However, its exact position is debated: some studies recover it alongside Achillobator outside Dromaeosaurinae, and a 2019 analysis noted it could shift positions with only two steps of change.

What we know

  • Sickle claw on the second toe was nearly 24 cm long — the largest known among dromaeosaurs.
  • Heavily built compared to other raptors, with thicker bones to support the larger body.
  • A massive sandstone block from Utah preserves multiple individuals stuck together — the 'Utahraptor megablock'.
  • Lived about 60 million years before Velociraptor.

What we guess

  • Whether the bonebed represents pack hunting or just multiple animals trapped by the same death trap.
  • Color and feather pattern — almost certainly feathered, but no preserved feathers have been found yet.
  • How it brought down prey much larger than itself — the leading idea is the 'raptor prey restraint' model.