Velociraptor

Restoration of Velociraptor

Velociraptor ("swift thief") is a genus of dromaeosaurid theropod dinosaur that lived in the Late Cretaceous of Mongolia. The familiar "raptor" has become one of the most well-known dinosaurs in recent years.

Description

Fully grown individuals of Velociraptor measured around 2 meters in length, half a meter high at the hips, and 15 kilograms in weight. Its skull measured up to 25 centimeters in length, and was slightly upcurved. The jaws had 26 to 28 teeth on each side, which were strongly serrated.

Like other dromaeosaurids, Velociraptor had a large hand with three strongly curved claws on each digit. Also like its relatives, the second digit of its foot was tipped with a sickle shaped claw. In Velociraptor, this claw could measure over 6.5 centimeters in length around its outer edge. The claw was probably used to tear into and disembowel prey.

Feathers

Other, more primitive dromaeosaurids are known to have extensive coverings of feathers on their bodies, and it was widely assumed that Velociraptor was similarly covered. This assumption was confirmed in 2007, when paleontologists reported that quill knobs had been found preserved on the forearm of a Velociraptor specimen. These structures, which are formed as bumps on the wing bones of modern birds to show where well-developed flight feathers anchor, indicate that Velociraptor had large and advanced feathers on its body.

Classification

Velociraptor was a dromaeosaurid, and more specifically a member of the subfamily Velociraptorinae. The contents of this subfamily are defined as "all dromaeosaurs more closely related to Velociraptor than to Dromaeosaurus." Originally, it was created solely to contain Velociraptor, but this has since been altered in several analyses.

Several different dromaeosaurid genera have been classified as Velociraptor in the past, but there are currently only two valid species in the genus: V. mongoliensis (the type species) and V. osmolskae.

The cladogram below is based on a 2009 analysis by Longrich and Currie:

Eudromaeosauria	Saurornitholestinae Saurornitholestes Atrociraptor Bambiraptor Deinonychus Velociraptorinae Velociraptor Itemirus Adasaurus Tsaagan Dromaeosaurinae Dromaeosaurus Utahraptor Achillobator

History

A drawing of the type skull and claw by Henry Fairfield Osborn

During an expedition by the American Museum of Natural History to the Gobi Desert of Mongolia, the first remains of Velociraptor (a complete skull and an associated sickle claw) were discovered in 1923, at a site known as the Flaming Cliffs. The following year, museum president Henry Fairfield Osborn described the fossils and named the new genus Velociraptor, meaning "swift thief". The specific name, mongoliensis, refers to the animal's country of origin.

When North American paleontologists were shut out of communist Mongolia during the Cold War, Soviet and Polish expeditions arose, in collaboration with Mongolian scientists. These expeditions recovered several new specimens of Velociraptor, the most famous of these being part of the "Fighting Dinosaurs" specimen, discovered in 1971. This remarkable fossil preserves a Velociraptor in the act of attacking a single Protoceratops.

A joint Chinese-Canadian team discovered Velociraptor fossils in northern China between 1988 and 1990. American paleontologists returned to Mongolia in 1990, and a joint expedition led by the American Museum of Natural History and the Mongolian Academy of Sciences discovered several well-preserved individuals of Velociraptor, among other remarkable specimens.

Skull material of Velociraptor recovered in 1999 from China were found to belong to the genus, but not to the same species. As such, a second species of Velociraptor, V. osmolskae, was named by Pascal Godefroit and colleagues in 2008, after the Polish paleontologist Halszka Osmólska.

Paleoecology

All known examples of V. mongoliensis have been found in the Djadochta Formation (also spelled Djadokhta), in the Mongolian province Ömnögovi. This formation dates to the Campanian stage of the Late Cretaceous Period, approximately 75 million years ago. This area was an arid environment at the time that Velociraptor lived, filled with sand dunes and little water. Additional fossils, namely those of V. osmolskae, have been found in the Bayan Mandahu Formation of Inner Mongolia, China, which had a similar environment. It is likely that frequent sandstorms contributed to the preservation of fossils in these regions.

V. mongoliensis shared its environment with dinosaurs such as Protoceratops and Oviraptor.

Paleobiology

Predatory behavior

An illustration of Velociraptor hunting Protoceratops, by Todd Marshall

Velociraptor actively hunted prey, as evidenced by the famous "Fighting Dinosaurs" specimen. The sickle claw on the animal's foot is traditionally depicted to have been used to slash at and disembowel prey. In the "Fighting Dinosaurs" specimen, this claw is apparently embedded in the throat of the Protoceratops, suggesting that the Velociraptor may have been using it to pierce through vital organs which were not protected by much skin and muscle. Various tests have shown that the sickle claw might not have been able to cut through the abdominal wall of normal prey animals very easily.

Several individuals of a related dromaeosaurid, the North American Deinonychus, have been found in association next to an individual of the ornithopod Tenontosaurus, suggesting that they may have hunted in packs. Although Velociraptor is widely depicted to have hunted in packs, there is currently no known fossil evidence for this assumption.

It was suggested in 2011 that Velociraptor and relatives may have had a unique method to capture and restrain prey. Called the "raptor prey restraint" (RPR) model of predation, this hypothesis proposes that dromaeosaurids killed their prey in a manner very similar to that of modern hawks and eagles: by jumping onto the victim, pinning it under their body weight, and then gripping it tightly with their specialized claws. This hypothesis is supported by the morphology of Velociraptor and others, and it is possible that the combined adaptations developed to hunt this way may have influenced the origin of wing flapping in paravians.

Scavenging habits

In 2010, paleontologist David Hone and colleagues described shed teeth of a Velociraptor found next to a tooth-marked Protoceratops bone in the Bayan Mandahu Formation. They interpreted this as scavenging behavior from a Protoceratops carcass. Another Velociraptor specimen described in 2012 had a pterosaur bone preserved in its stomach, which was also interpreted as having been scavenged.

Pathology

A skull of V. mongoliensis bears two parallel rows of small punctures that match the tooth patterns of a Velociraptor jaw. It is believed that the wound was inflicted by another Velociraptor during a fight. As the bone shows no sign of subsequent healing near the punctures, the wound likely killed the animal.

In popular culture

Velociraptor is one of the most familiar of dinosaurs thanks to their appearance in the 1990 novel Jurassic Park and the subsequent film series. The "raptors" portrayed in the franchise were in fact more heavily modeled after Deinonychus, which was at the time of the novel classified by Gregory Paul as a species of Velociraptor, V. antirrhopus. They were depicted as being much larger than real Velociraptor, and featherless, due to the fact that feathers had not been discovered in dinosaurs until after the novel and first film.

Although relatively unknown before Jurassic Park, Velociraptor soon after became one of the most familiar dinosaurs in popular culture, appearing in several television programs, games, and toy lines. The Toronto Raptors, an NBA basketball team, was named after Velociraptor.