Introduction to the Raptors

Dromaeosaurids are a family of feathered theropod dinosaurs that lived during the Cretaceous period, made famous by the "Velociraptors" in the Jurassic Park franchise. Often nicknamed "raptors," well-known members of this group include Dromaeosaurus, Velociraptor, Utahraptor, and Dakotaraptor.

Although the Jurassic Park franchise portrays dromaeosaurs such as Velociraptor as scaly, lizard-like monsters, they were actually far more bird-like in both appearance and anatomy. Birds and dromaeosaurids share a common ancestor dating back to the early Jurassic period. As a result, they share many features, including hollow bones, flight feathers, wing-like arms, stiffened tails, and even a wishbone. In fact, dromaeosaurids, troodontids, and birds are all grouped together within the Paravian clade due to these strong evolutionary similarities.

In general, raptors were bipedal predators with bodies built for speed and agility. Their long, fully feathered arms closely resembled wings, while their tails were stiffened with tendons for balance. This combination of wings for stability and tails for counterbalance made them highly agile and maneuverable hunters. Interestingly, raptors walked and ran on only two of their three front toes - the raised inner toe carried a large, retractable claw used for hunting. They also had forward-facing eyes, providing excellent depth perception. To support their coordination and vision, their brains were relatively large compared to other dinosaurs (though still smaller than those of mammals). Altogether, raptors were highly specialized and efficient predators.

Most dromaeosaurids were relatively small, about the size of a turkey. However, some species grew much larger, with a few reaching heights comparable to an adult human. Notable examples of these larger raptors include Utahraptor and Dakotaraptor from the North American Cretaceous.

Many smaller dromaeosaurids likely used their wings and claws to help climb trees. Some species were arboreal, living and hunting among branches, while others may have been capable of gliding or even limited flight. One of the most famous examples is Microraptor gui, a four-winged dromaeosaur with flight feathers on both its arms and legs, as well as a tail that could generate lift. To learn more about flying dromaeosaurs, check out my flying dinosaurs article.

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Feathers

Raptors were fully feathered, including wings.

When paleontologists say raptors were feathered, they don't mean a lizard-like animal with a few scruffy feathers. Dromaeosaurids were fully feathered, more like modern birds such as falcons, with long wing feathers and elaborate tail plumage.

How do we know this? For more than 20 years, exceptionally preserved dinosaur fossils from Liaoning Province, China, have revealed remarkable details of soft tissue and feather preservation. Numerous dromaeosaurid specimens from these deposits show complete feather coverage. In fact, many of them look strikingly bird-like.

More recently, a larger dromaeosaurid, approximately 1.6 meters long, called Zhenyuanlong suni was discovered in these same deposits (Lu and Brusatte, 2015). This specimen is also extensively feathered, with well-developed wing feathers (except on parts of the legs). Its discovery provides strong evidence that even larger dromaeosaurids were fully feathered.

Outside of Liaoning Province, where dinosaur fossils typically lack soft tissue preservation, scientists can still determine the presence of feathers by examining bone structure. Bird bones often display quill knobs, or small bumps, on the ulna (arm bone) that serve as anchor points for secondary feathers. Well-preserved dromaeosaurid arm bones show these same features. Notable examples of quill knobs in larger dromaeosaurids include Velociraptor from Mongolia (Turner et al., 2007), Dakotaraptor from South Dakota (DePalma et al., 2015), and Dineobellator from New Mexico (Jasinski et al., 2020). All of these species exhibit quill knobs on their forearms, providing strong evidence that they had fully feathered wings.

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The Killing Claw

It wasn't really a Killing Claw

All dromaeosaurids possessed a distinctive, enlarged sickle-shaped claw on the second toe of each foot. This claw was typically held off the ground while walking and could be brought down when needed to engage prey. Its prominence in popular culture has earned it the nickname "killing claw."

It is common to see depictions of raptors leaping onto the sides of much larger dinosaurs, gripping with their arms while slashing through flesh with this claw. These dramatic scenes are deeply ingrained in popular imagination, but how accurate are they? Did dromaeosaurids really use their claws to slash and disembowel large prey?

To the disappointment of many Jurassic Park fans, the answer appears to be no. A study by Manning et al. (2006) modeled dromaeosaur hind limbs and found that the claw was not well-suited for slashing. Rather than tearing flesh, the claw tended to pierce without causing significant slicing damage, and it could even break when used against thick hide. A later study by Peter Bishop (2019), which analyzed the forces generated by raptor feet and claws in different positions, found that the force at the claw tip was relatively low. Together, these studies suggest the claws were better adapted for grasping and restraining prey rather than cutting it.

In 2011, Fowler et al. examined the combined function of the hind limbs and forelimbs to better understand dromaeosaur feeding behavior. They proposed that the claw was primarily used to grip and pin down smaller, struggling prey. Their feathered forelimbs likely helped maintain balance by flapping, rather than actively grasping. This behavior closely resembles that of modern birds of prey, which use their talons to immobilize prey while stabilizing themselves with wing movements. Unlike birds, however, dromaeosaurids had jaws filled with numerous small, serrated teeth that functioned like a set of steak knives.

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Cooperative Pack Hunting?

Probably not

So, the "killing claw" was not used to slash and disembowel large prey. What about pack hunting? Did raptors cooperatively take down large dinosaurs? Evidence suggests they likely did not.

The idea of pack hunting dates back to the late 1960s, when John Ostrom studied Deinonychus fossils found alongside Tenontosaurus and proposed coordinated group hunting. However, more recent research suggests these sites were likely scavenging events, where multiple raptors fed on carcasses�including those of their own species.

Other fossil discoveries show multiple raptors preserved together, but this does not necessarily indicate social behavior. A well-known example is the Utahraptor "megablock," which is often interpreted as a predator trap similar to the La Brea Tar Pits, where animals became stuck in mud and attracted scavengers that were also trapped.

In 2009, Roach and Brinkman examined this question and found evidence of intraspecies aggression, including cannibalism. They concluded that dromaeosaurids were likely solitary hunters or, at most, loosely associated foragers. Supporting this, a 2020 study by Frederickson et al. analyzed isotope ratios in Deinonychus teeth and found differences between juveniles and adults�similar to modern crocodilians. This suggests they did not feed their young, a behavior inconsistent with social, pack-hunting animals.

One piece of evidence for group behavior comes from fossil trackways. In 2007, Li et al. described six parallel dromaeosaur trackways moving in the same direction, indicating that multiple individuals traveled together. However, this does not confirm pack hunting�they may simply have been moving toward a food source.

Finally, while raptors had relatively large brains for dinosaurs, they were still small compared to mammals and more similar to crocodilian brains. Complex cooperative hunting requires higher cognitive abilities, which may have been beyond their capacity.

Overall, the evidence suggests raptors were primarily solitary, opportunistic predators. Their behavior may have resembled modern Komodo dragons�generally solitary, but gathering at carcasses where competition could become aggressive and even cannibalistic.

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Examples of Popular Raptors

Raptors are prominent in pop culture, but unfortunately are often portrayed unscientifically. To show what some raptors were actually like, below is a brief overview of a few of the more popular ones:

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Velociraptor

Not your Jurassic Park 'Velociraptor'

When the word Velociraptor is mentioned, most people think of Jurassic Park. However, the Jurassic Park 'Velociraptors' are nothing like the actual Velociraptors. It’s better to consider the Jurassic Park Franchise movies as entertaining monster movies.

The name Velociraptor means “Swift Seizer,” and they lived in desert-like conditions in the Late Cretaceous of Mongolia. There are currently two species of Velociraptor: V. mongolienses and V. osmolskae. Velociraptors could reach lengths of around 7 feet, but most of that was their long and stiff tail. Mass wise, they were about the size of a medium dog, maybe around 30 pounds. Velociraptors also had a relatively long and upturned snout.

Recent research shows they had large eyes, indicative of good night vision, so they may have been nocturnal hunters (Choiniere et al., 2021), feeding on small animals and similar sized dinosaurs. They were also fully feathered. Some of the specimens have preserved quill knobs on their arms, where secondary feathers would attach. This means their arms looked more like wings. Often times they are depicted as being scaly, or as a chicken with mange. However, they would have looked more like a bird, fully feathered. One notable fossil shows a Velociraptor in a death match with a small Ceratopsian dinosaur. It appears they both died together while fighting, then were buried when a sand dune collapsed.

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Utahraptor

Giant Early Cretaceous raptor of North American

Standing over 6-foot-tall and 23 feet long, Utahraptor is the largest raptor yet discovered. The first fossil was found in 1991 just when Jurassic Park was being filmed. Fossils of this animal are found in the Cedar Mountain Formation near Arches National Park in Utah which is Early Cretaceous (125-130 million years old).

The Utahraptor Block

The most famous fossil find of these animals is the “Utahraptor Megablock” which is a 9-ton block that contains thousands of Utahraptor bones of all ages. Discovered by Matthew Stikes in 2005, preparation of this block will take years. As paleontologists continue to excavate, they hope to find fine details, including feather impressions. This block also contains two iguanodont dinosaurs. Paleontologists believe these raptors may have been group feeding on these carcasses that were trapped in quicksand and became trapped themselves.

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Dakotaraptor

Giant Late Cretaceous raptor of North America

Dakotaraptor is the largest raptor discovered thus far in the Hell Creek formation. Standing over 6 feet tall and 20 feet in length, Dakotaraptor was similar in size to the earlier Utahraptor. It lived alongside iconic Late Cretaceous dinosaurs such as Triceratops and T. rex and was also one of the last living dinosaurs, right up to the end Cretaceous extinction event. The genus name comes from the discovery location in South Dakota and the species name honors Walter Stein of Paleoadventures.

Dakotaraptor is also the largest raptor that preserves evidence of feathers. Well preserved fossils show quill knobs on its arm bones, indicating it had fully feathered wings (DePalma et al, 2015). The anatomy of the hind limbs indicate Dakotaraptor was a very fast and agile dinosaur capable of outrunning most other dinosaurs.

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Deinonychus

The raptor that changed everything

Deinonychus was a 7-10 foot long raptor of the Early Cretaceous of North America. Deinonychus means “Terrible Claw” after its large toe claw. This is a special raptor because it paved the way to our modern understanding of dinosaurs. Previous to this 1969 discovery, dinosaurs were often thought of as large, slow, and cold blooded. The discovery of this nimble bird-like predator built for speed and agility made paleontologists re-think the classic views of dinosaurs.

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Acheroraptor

The first official raptor of the Hell Creek

Acheroraptor was a Deinonychus sized raptor with a long snout similar to that of Velociraptor. Although Dromaeosaurid teeth are common in the Hell Creek Formation, their bones are incredibly fragile, and thus rare. As a result, it wasn’t until 2013 that skull material from a raptor was found in the Hell Creek. This skull material was assigned to Acheroraptor, and it became the first confirmed raptor of the Hell Creek Formation.

Isolated Acheroraptor teeth are found throughout the Hell Creek and are easy to identify due to longitudinal striations on the tooth enamel.

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Microraptor

The 4-winged flying raptor

Microraptor is probably the most famous flying dinosaur. This crow sized raptor was covered in black iridescent feathers and had long flight feathers on both its arms and legs, making it a four-winged dinosaur! The long feathers on the tail could also generate lift. Although it has a plethora of wings, it was not a graceful flyer, more like a fat chicken. The claws on its arms were specialized for climbing, so it may have lived in the forest canopy flying from tree to tree. To learn much more about Microraptors and other flying dinosaurs, check out the flying dinosaurs article.

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Recommended Dinosaur Books and Educational Items:

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High quality Dinosaur teeth by Fossilera

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Bishop PJ (2019) Testing the function of dromaeosaurid (Dinosauria, Theropoda) ‘sickle claws’ through musculoskeletal modelling and optimization. PeerJ DOI:doi.org/10.7717/peerj.7577

Choiniere JN, Neenan JM, Schmitz L, Ford DP, Chapelle KEJ, Balanoff AM, Sipla JS, Georgi JA, Walsh SA, Norell MA, Xu X, Clark JM, Benson RBJ (2021) Evolution of vision and hearing modalities in theropod dinosaurs. Science. 2021 May 7;372(6542):610-613. DOI:10.1126/science.abe7941

Depalma, Robert & Burnham, David & Martin, Larry & Larson, Peter & Bakker, Robert (2015) The first giant raptor (Theropoda: Dromaeosauridae) from the Hell Creek Formation. Paleontological Contributions. 14. DOI: doi.org/10.17161/paleo.1808.18764

Fowler DW, Freedman EA, Scannella JB, Kambic RE (2011) The predatory ecology of Deinonychus and the origin of flapping in birds. PLOS ONE 6:e28964 DOI:doi.org/10.1371/journal.pone.0028964

Fowler DW, Freedman EA, Scannella JB (2009) Predatory functional morphology in raptors: interdigital variation in talon size is related to prey restraint and immobilisation technique. PLOS ONE 4:e7999 DOI:https://doi.org/10.1371/journal.pone.0007999

Frederickson JA, Engel MH,Cifelli RL (2020) Ontogenetic dietary shifts in Deinonychus antirrhopus (Theropoda; Dromaeosauridae): Insights into the ecology and social behavior of raptorial dinosaurs through stable isotope analysis, Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 552, DOI:doi.org/10.1016/j.palaeo.2020.109780

Jasinski SE, Sullivan RM, Dodson P (2020) New Dromaeosaurid Dinosaur (Theropoda, Dromaeosauridae) from New Mexico and Biodiversity of Dromaeosaurids at the end of the Cretaceous. Sci Rep 10, 5105 DOI:doi.org/10.1038/s41598-020-61480-7

Li, R, Lockley, MG, Makovicky, PJ et al. (2008) Behavioral and faunal implications of Early Cretaceous deinonychosaur trackways from China. Naturwissenschaften 95, 185–191. DOI:https://doi.org/10.1007/s00114-007-0310-7

Manning PL, Payne D, Pennicott J, Barrett PM, Ennos RA (2006) Dinosaur killer claws or climbing crampons? Biol Lett 22: 110–112. DOI: doi.org/10.1098/rsbl.2005.0395

Maxwell W Desmond & Ostrom John H (1995) Taphonomy and paleobiological implications of Tenontosaurus-Deinonychus associations, Journal of Vertebrate Paleontology, 15:4, 707-712, DOI: 10.1080/02724634.1995.10011256

Turner, Alan & Makovicky, Peter & Norell, Mark (2007) Feather Quill Knobs in the Dinosaur Velociraptor. Science (New York, N.Y.). 317. 1721. DOI:doi.org/10.1126/science.1145076

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FAQs: Dromaeosaurid Frequently Asked Questions

• What are Dromaeosaurids?
  Dromaeosaurids are a family of feathered theropod dinosaurs that lived during the Cretaceous Period. Often called raptors, they include Velociraptor, Deinonychus, Utahraptor, Dakotaraptor, and Microraptor. These agile, bipedal predators were closely related to birds.
• Were raptors really feathered?
  Yes. Fossils from China preserve full feather coverings on many Dromaeosaurids, and larger species show quill knobs on their arm bones where wing feathers attached. Raptors were fully feathered animals that looked far more like birds than scaly reptiles.
• Did Velociraptors look like they do in Jurassic Park?
  No. Real Velociraptors were about the size of a turkey and were fully feathered. The Jurassic Park version was based largely on Deinonychus and portrayed as a much larger, scaly reptile for cinematic effect.
• What was the raptor “killing claw” used for?
  Scientific studies suggest the enlarged sickle-shaped claw on the second toe was used for grasping and pinning prey rather than slashing open large dinosaurs. Biomechanical research shows it functioned more like the talons of modern birds of prey.
• Did raptors hunt in packs?
  Current evidence suggests most raptors were likely solitary hunters. Isotope studies and fossil evidence indicate they did not feed their young in social groups and may have behaved more like crocodilians or Komodo dragons, occasionally feeding together at carcasses but not hunting cooperatively.
• How big was Velociraptor?
  Velociraptor measured about 6–7 feet long including its stiff tail and weighed roughly 30 pounds, making it about the size of a medium dog. It lived in Late Cretaceous Mongolia.
• What is the largest raptor dinosaur discovered?
  Utahraptor is considered the largest known raptor, reaching lengths of about 23 feet and standing over 6 feet tall. Dakotaraptor was similarly large and lived later in the Late Cretaceous of North America.
• Was Microraptor a flying dinosaur?
  Yes. Microraptor was a small, crow-sized raptor with long flight feathers on both its arms and legs, giving it four wings. Fossil evidence suggests it could glide or fly between trees.
• Are birds related to raptors?
  Yes. Dromaeosaurids and birds share a common ancestor and belong to the Paravian group of theropods. They share features such as hollow bones, feathers, wishbones, and similar body structures.
• Where have Dromaeosaur fossils been found?
  Dromaeosaur fossils have been found across North America, Mongolia, and China. Exceptional feathered specimens come from Liaoning Province in China, while large species like Utahraptor and Dakotaraptor are known from North America.
• Why is Deinonychus important in dinosaur history?
  The discovery of Deinonychus in 1969 helped revolutionize our understanding of dinosaurs. Its agile, bird-like anatomy supported the idea that many dinosaurs were active, fast-moving animals rather than slow, cold-blooded reptiles.
• Did raptors climb trees?
  Many small Dromaeosaurids had curved claws and feathered wings that likely helped them climb trees. Some species, such as Microraptor, may have lived in forest canopies and glided between trees.

Dromaeosaurid Article FAQ's

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