Utahraptor

April 4, 2022 Scott Kraus

Utahraptor, which means “Utah’s predator”, is a theropod dinosaur that lived about 125 million years ago in the early Cretaceous era. It’s thought to have been the largest raptor that ever lived (ironically, the two ton “Gigantoraptor” from central Asia isn’t even in the running because it was just a large theropod dinosaur, not a raptor). Adult Utahraptors measured about 25 feet from head to tail and weighed 1 to 2 tons

Quick Facts

What did Utahraptor Look Like?

The Utahraptor is the largest in the family of Dromaeosauridae, of which Velociraptor is also a member, and as such display a number of physical characteristics unique to the order. 

First, throw out the notions of Jurassic Park, and the tall reptilian looking Velociraptors that hunted in packs and had highly evolved social and linguistic skills.  There is no evidence to support that, particularly the ability to coordinate with language. There is some evidence of dromeosaurs attacking larger prey, but this is hotly debated. There’s good reason to believe multiple raptors found dead at a kill site were the result of bickering between themselves rather than evidence they hunted in packs.

With that said, in 2015 there was a discovery of several Utahraptors buried together after they fell in quicksand! Was it because they moved in a pack like wolves, or did the struggled cries of a caught Iguanadont and Utahraptor inspire bloodlust in others nearby? It’s hard to tell if this is pro-social behavior.

Keep an eye out for updates though! Though evidence for raptor group-think is scant, this set of tracks found in China may be all that’s needed to prove they were indeed social pack hunters.

There is however a much more interesting dinosaur at the truth of the matter.  The Utahraptor was a sleek, feathered, bipedal carnivore. It is significantly larger than the velociraptor, at least as tall as a human and many times heavier. It also had a narrow, sharply defined snout, and forward looking eyes.  Its tail would stretch out behind it to stabilize the massive animal at high speeds.

Physical Attributes of Utahraptor

The specialized second toe of the Utahraptor was its main device for catching prey.  On its foot, the first and third digit were placed on the ground, transferring all of the weight of the animal through those two toes on each foot.  The middle claw held a slicing/puncturing talon, held retracted while moving.  This adaption was common among Dromaeosauridae.  The eye placement in the skull was also an adaption used to hunt prey.  The binocular effect made the Utahraptor have excellent vision.

Utahraptor Had Feathers

Covered in feathers, the Utahraptor exemplifies the connection between prehistoric dinosaurs and birds.  The evolutionary process had robbed the dinosaur of the main flight feathers seen in flying birds, and instead it had shorter, proto-feathers covering its upper body.  It would have had some use for these feathers however, as the Utahraptor may have flapped its wings to run faster, jump higher, and maintain balance atop prey animals.

What did Utahraptor eat?

The Utahraptor was the dominant carnivore in its ecosystem.  Scientists have found no evidence of a larger land predator during the animals lifespan. There is evidence of a close relative of Utahraptor, the North American raptor called Deinonychus, hunting in packs.

It’s very possible that Utahraptor wouldn’t have needed to hunt in packs since it was so large. Scientists believe that the diet of Utahraptor was comprised mostly of Iguanadons, a large herbivore of the same Early Cretaceous period. They also think that it had some kind of warm-blooded metabolism. Perhaps not to the extent of modern mammals, but something between reptiles and mammals. Considering it’s size, level of activity, and the presence of feathers it would be very sensible to conclude that Utahraptor had a metabolism that was endothermic.

History and Discovery of Utahraptor

The First Utahraptor fossils were found by Jim Jensen in 1975 at the Dalton wells Quarry in east-central Utah, but this news mostly slipped under the radar. Further Utahraptor remains were found in 1991 spurred on by the find of a large foot-claw by Carl Limoni. Brigham Young University now has the biggest collection of Utahraptor bones, but the official type fossil is at the College of Eastern Utah Prehistoric Museum. Utahraptor is a single named species, known as Utahraptor ostrommaysorum. The name honors both John Ostrom, the famous American paleontologist, and Chris Mays, the pioneer of dinosaur robotics. Ostrom was one of the first to speculate that raptors shared significant traits with birds.

Utahraptor is obviously named after the state, but it almost had another famous name attached to it. The species was originally going to be named “Utahraptor spielbergi” after the movie director Steven Spielberg, in exchange for him funding palaeontological research. But there was no agreement on the amount of funding.

Historical Significance of Utahraptor

The history of this dinosaur is relatively new.  Filmmakers of the blockbuster hit “Jurassic Park” made the controversial move to double the size of the Velociraptor, approximately the size of the Utahraptor, this dinosaur had yet to be discovered.  If it had, it is likely that they would have replaced Velociraptor with the Utahraptor and it would be as well known as the Velociraptor is today.