Velociraptor

Velociraptor is a genus of small dromaeosaurid dinosaurs. They lived in Asia during the Late Cretaceous epoch, about 75 million to 71 million years ago (Mya). Its name means "swift thief." Scientists currently recognize two species, although others have been named in the past. The type species is V. mongoliensis, which was named and described in 1924. Fossils of this species have been found in the Djadochta Formation in Mongolia. The second species, V. osmolskae, was named in 2008. It is based on skull material from the Bayan Mandahu Formation in China. A possible record of the genus is known from the Nemegt Formation.

Velociraptor was smaller than other dromaeosaurids, such as Deinonychus and Achillobator. It was about 1.5 to 2.07 m (4.9 to 6.8 ft) long and weighed around 14.1 to 19.7 kg (31 to 43 lb). Even so, it had many of the same anatomical features as its larger relatives. It was a bipedal, feathered carnivore. It had a long tail and an enlarged, sickle-shaped claw on each hind foot. Scientists think this claw was used to grab and hold prey. You can tell Velociraptor apart from other dromaeosaurids by its long, low skull and its upturned snout.

Velociraptor, often called "raptor," is one of the dinosaurs that most people know best. This is thanks to its prominent role in the Jurassic Park films. In reality, Velociraptor was about the size of a turkey. The creatures in the novels and films were much bigger, about 2 m (6.6 ft) long and 90 kg (200 lb). Those creatures were based on members of the related genus Deinonychus.

Today, Velociraptor is well known to paleontologists, who have studied over a dozen fossil skeletons. One particularly famous specimen shows a Velociraptor locked in a struggle with a Protoceratops.

History of discovery

In 1923, an expedition from the American Museum of Natural History went to the Flaming Cliffs (Bayn Dzak or Bayanzag) in the Gobi Desert. There, Peter Kaisen found the first Velociraptor fossil known to science. It was a damaged but complete skull. In 1924, museum president Henry Fairfield Osborn gave the animal its name, Velociraptor. The name comes from the Latin words velox ('swift') and raptor ('robber' or 'plunderer'). Osborn named the main species V. mongoliensis after the animal's home country. Earlier that year, he had written about the animal in a popular article under the name "Ovoraptor djadochtari." That name was later changed. It should not be confused with the similar name Oviraptor.

During the Cold War, communist Mongolia was closed to teams from North America. Scientists from the Soviet Union and Poland worked with Mongolian colleagues and found more Velociraptor fossils. The most famous is the "Fighting Dinosaurs" fossil, found in 1971. It shows a Velociraptor and a Protoceratops locked in a struggle. Mongolia considers it a national treasure. In 2000, it was loaned to the American Museum of Natural History in New York City. From 1988 to 1990, a team from China and Canada found remains in northern China. In 1999, Rinchen Barsbold and Halszka Osmólska reported a young Velociraptor with a complete skeleton, including its skull.

Additional species

Description

Velociraptor was a small to medium-sized dromaeosaurid. Adults were about 1.5–2.07 m (4.9–6.8 ft) long. They stood about 0.5 m (1.6 ft) tall at the hips and weighed about 14.1–19.7 kg (31–43 lb). Some estimates suggest it may have grown to about 2.5 m (8 ft) long and 28 kg (60 lb). Its skull could be up to 23 cm (9.1 in) long, with a narrow snout. The snout was formed mainly by the nasal and premaxilla bones. Its teeth sat in alveoli (or tooth sockets). They were fairly homodont, which means they were similar in shape. Small denticles (serrations) lined their edges.

The arm was made of the humerus, radius, and ulna. It ended in a large manus (hand) with three digits (fingers). These fingers had strongly curved claws. The claws were similar to the wing bones of modern birds. The second toe had a large, sickle-shaped claw. It was probably used to hold onto struggling prey.

One specimen has quill knobs on its ulna. These are bumps where "wing" feathers attached. This shows that Velociraptor had a feather covering. Its secondaries, the large feathers that grew from the forearm, were probably attached there too. Other related dromaeosaurids, such as Daurlong, Microraptor, and Zhenyuanlong, also provide phylogenetic evidence that Velociraptor had feathers. The tail had prezygapophyses (long bony projections) on its vertebrae. These were once thought to make the tail completely stiff. However, one specimen shows that the tail could bend sideways much more than scientists first believed.

Classification

Velociraptor belongs to the group Eudromaeosauria, a derived sub-group of the larger family Dromaeosauridae. It is often placed in its own subfamily, Velociraptorinae. Scientists who use phylogenetic taxonomy usually define Velociraptorinae as "all dromaeosaurs more closely related to Velociraptor than to Dromaeosaurus." How dromaeosaurs are classified varies a lot. Some studies have included Deinonychus and Saurornitholestes, and more recently Tsaagan. Several studies from the 2010s did not show Velociraptorinae as a clear separate group. Instead, they suggested it was a group that gave rise to the Dromaeosaurinae.

When Velociraptor was first described in 1924, it was placed in the family Megalosauridae. At that time, most meat-eating dinosaurs were grouped there. This family was like a "wastebin," holding many unrelated species, such as Megalosaurus. Later, as more dinosaurs were found, Velociraptor was recognized as a dromaeosaurid. At least one author also placed all dromaeosaurids in the family Archaeopterygidae. Some other dromaeosaurs were once placed in the genus Velociraptor. Because Velociraptor was named first, they were given new names: Velociraptor antirrhopus and V. langstoni. As of 2008, only two species were recognized: V. mongoliensis and V. osmolskae. However, several studies found that V. osmolskae is only distantly related to V. mongoliensis.

Below are the results for the Eudromaeosauria phylogeny. They come from the phylogenetic analysis done by James G. Napoli and his team in 2021, when they described Kuru. The results show where Velociraptor fits:

Paleobiology

In 2007, Alan H. Turner and colleagues reported six quill knobs on the ulna of a Velociraptor specimen from the Ukhaa Tolgod area of the Djadochta Formation. They suggested that the ancestors of dromaeosaurids could fly, and that Velociraptor lost the ability to fly because of its large size. Its feathers may have been used for display, for covering nests, or for speed when running up slopes. Another dromaeosaurid, Tsaagan, was also found at Ukhaa Tolgod, so Napoli and team noted that the link of this specimen to Velociraptor is being reexamined.

Studies of the brain case showed that Velociraptor could hear a wide range of sounds and could track prey easily. It was an agile, swift hunter. Fossil evidence also suggests that it scavenged, eating dead animals during droughts or famines, when it was sick, or depending on its age.

In 2020, Powers and colleagues studied the maxillae of several eudromaeosaur species. The maxilla helps show the shape of the premaxilla and the overall snout. Most Asian species, such as the velociraptorines, had long snouts, which suggests that Velociraptor picked up small, fast prey. In 2022, Manabu Sakamoto estimated bite forces. Velociraptor had a bite force of 304 N, which was lower than that of Dromaeosaurus (885 N) and Deinonychus (706 N).

The "Fighting Dinosaurs" specimen, found in 1971, shows a Velociraptor mongoliensis and a Protoceratops andrewsi locked in a fight. This is direct evidence of hunting behavior. The two animals were probably buried quickly in sand, from a collapsing dune or a sandstorm. Parts of the Protoceratops are missing, which may show scavenging by other animals. Comparisons of eye rings suggest that Velociraptor may have been nocturnal, while Protoceratops may have been cathemeral. The fight may have happened at twilight or in low light.

The large claw on the second toe was once thought to slash open the belly of prey. In the Fighting Dinosaurs specimen, one sickle claw seems to be at the throat of its prey. This suggests Velociraptor may have used the claw to pierce the jugular vein, carotid artery, or trachea, rather than slashing the belly. A 2005 BBC documentary, The Truth About Killer Dinosaurs, tested the slashing hypothesis with a model leg and a pork belly. The claw pierced the skin and muscle but could not tear them open.

Deinonychus fossils are often found in groups, and it has been found with Tenontosaurus, which some researchers cite as evidence of working together to hunt. However, Velociraptor is often shown as a pack hunter, as in Jurassic Park, and its fossils were not found near other individuals. In 2011, Denver Fowler and colleagues proposed that dromaeosaurs pinned prey as accipitrid birds of prey do, by leaping onto it and gripping it with their claws. Their feet and legs most closely resemble those of eagles and hawks, though the short metatarsus is more like that of owls. The jaws may have been used for a sawing bite, like that of the Komodo dragon, to finish off prey. These ideas may also relate to the origin of flapping in paravians.

In 2010, Hone and colleagues described shed teeth near a tooth-marked jaw of a Protoceratops, which suggests that Velociraptor ate parts of a recently caught animal. In 2012, Hone and team described a Velociraptor with a bone of an azhdarchid pterosaur in its gut, which was interpreted as scavenging. A 2024 study found that Velociraptor resisted high bite forces better than other dromaeosaurids, which may mean it got much of its food by scavenging.

Velociraptor was somewhat warm-blooded, since hunting needed a lot of energy and its feathers would have kept it warm. However, bone growth in dromaeosaurids suggests a more moderate metabolism than most modern warm-blooded animals. The kiwi is similar to dromaeosaurids in several ways. In 2023, Seishiro Tada and team studied the nasal cavities of ectotherm and endotherm species to compare their thermoregulatory physiology. They suggested that Velociraptor may not have had a well-developed system for controlling body temperature in the nose, as modern endotherms do.

Main article: Theropod paleopathology

In 1995, Norell and colleagues reported a skull with two rows of small punctures that match the spacing and size of Velociraptor teeth. They suggested the wounds came from a fight within the species. Because the bone showed no sign of healing, this individual likely died from the wound. In 2012, David Hone and team reported an injured young adult Velociraptor with the bones of an azhdarchid pterosaur in its stomach. Its broken rib showed signs of healing, and the animal may have died shortly after.

Paleoenvironment

The Bayan Mandahu and Djadochta formations had many of the same kinds of animals, though the species were often different. These differences may come from a natural barrier between the two formations, which are fairly close to each other. However, no known barrier would explain the different animal groups found in these areas. The differences more likely show a small difference in time. V. osmolskae lived alongside the ankylosaurid Pinacosaurus mephistocephalus; the alvarezsaurid Linhenykus; the close relative Linheraptor; the oviraptorids Machairasaurus and Wulatelong; the protoceratopsids Bagaceratops and Protoceratops hellenikorhinus; and the troodontids Linhevenator, Papiliovenator, and Philovenator. The rocks across the formation show a environment similar to that of the Djadochta Formation.

Known fossils of Velociraptor mongoliensis have been found in the Djadochta Formation (also spelled Djadokhta), in the Mongolian province of Ömnögovi. This geological formation is estimated to date back to the Campanian stage, between 75 million and 71 million years ago, during the Late Cretaceous epoch. Its many sandstones, caliche, and sands were formed by eolian (wind) processes in dry areas with dunes and only occasional streams, under a semi-arid climate. The formation is divided into a lower Bayn Dzak Member and an upper Turgrugyin Member, and V. mongoliensis is known from both. The Bayn Dzak Member has produced the oviraptorid Oviraptor, the ankylosaurid Pinacosaurus grangeri, the protoceratopsid Protoceratops andrewsi, and the troodontid Saurornithoides. The younger Turgrugyin Member has produced the bird Elsornis, the dromaeosaurid Mahakala, the ornithomimid Aepyornithomimus, and Protoceratops andrewsi. The type specimen of V. mongoliensis was found at the Flaming Cliffs site. The "Fighting Dinosaurs" were found at the Tugrik Shire locality, which is known for its excellent in situ fossil preservation. Some layers, such as plain sandstones, suggest that many animals were buried during strong sand-bearing events that were common in these areas.

Cultural significance

Velociraptor is often seen as a fierce and clever animal, mostly because of the 1990 novel Jurassic Park by Michael Crichton and its 1993 film adaptation, directed by Steven Spielberg. The "raptors" in Jurassic Park were actually based on a close relative, the dromaeosaurid Deinonychus. In both the novel and the film, scientists dig up a skeleton in Montana. Velociraptor did not live there. It lived in central Asia. But Deinonychus was found in Montana. Crichton met several times with Deinonychus discoverer John Ostrom at Yale University. Crichton told Ostrom that he had used the name Velociraptor because it sounded "more dramatic." Ostrom said that the animal in the novel was based on Deinonychus in almost every detail. The filmmakers also asked for Ostrom's papers on Deinonychus and used its size, body shape, and snout shape for the animals in the film.

Filming began before the large dromaeosaurid Utahraptor was made public in 1991. Later, a raptor skeleton found in Utah turned out to be about the same size as the film's raptors. Spielberg's name was briefly considered for the new dinosaur in exchange for funding, but no agreement was reached. Jurassic Park and its sequel The Lost World: Jurassic Park came out before scientists learned that dromaeosaurs had feathers. So their Velociraptor had scales and no feathers. In Jurassic Park III, the male had quill-like structures on its head and neck. However, these did not look like the feathers Velociraptor would really have had. The Jurassic World films kept the designs from Jurassic Park. But the dromaeosaur Pyroraptor was given feathers in Jurassic World Dominion.