Velociraptor

Credit: Fred Wierum.

*Velociraptor* is an extinct genus of dromaeosaurid dinosaur that lived in Mongolia during the Late Cretaceous.

## History

An American Museum of Natural History expedition on August 11, 1923 in the Gobi Desert recovers the first *V. mongoliensis*; a crushed, complete skull with 1/2 raptorial sickle claws, catalogued AMNH 6515. Henry Fairfield (1924) thought the skull and claw (which he thought was of the hand) as the type of a new genus, *Velociraptor*. Earlier that year, Osborn mentioned the animal in a news article under the name "Ovoraptor djadochtari", which was not formally published, leading to it being a nomen nudum and Velociraptor taking priority.

With North American teams shut out of Mongolia during the Cold War, expeditions by Polish and Soviet scientists, collaborating with Mongolian colleagues, found more *Velociraptor* specimens. The most famous is the Fighting Dinosaurs (GIN 100/25), found by a Polish/Mongolian team (1971). It is a *Velociraptor* and *Protoceratops* locked in battle, still articulate. It is considered a national treasure in Mongolia, being loaned in 2000 to the American Museum of Natural History for an exhibition.

A Chinese-Canadian joint team (1988-1990) found more *Velociraptor* in north China. American scientists returned to Mongolia in 1990, with a joint Mongolian-American expedition led by the American Museum of Natural History and the Mongolian Academy of Sciences found more well-preserved *Velociraptor*. IGM 100/980, one of the specimens and nicknamed Ichabodcraniosaurus, was originally attributed to *V. mongoliensis*, being named *Shri* in 2021.

Maxillae and a lacrimal found in 1999 by the Sino-Belgian Dinosaur Expeditions found a *Velociraptor* species non-referable to *V. mongoliensis*, erecting *V. osmolskae* after Halszka Osmólska by Pascal Godefroit et al. (2008). However, some suggest this species should be reevaluated, since it occupies a position that would traditionally call for a new genus.

*Velocirator* was used by S. Chao (1980) as a lapsus for *V. mongoliensis* in a revision.

## Description

*Velociraptor* was a medium-sized dromaeosaurid, with adults up to 2.07 meters (6 ft 9+1⁄2 inches) long, 0.5 meters (1 ft 7+1⁄2 inches) high (at the hip) and up to 15 kilograms (33 pounds) in weight. However, higher estimates find 19.7 kilograms (43+1⁄2 pounds). The skull is up to 25 centimeters (10 inches) long, being upturned (unique to the genus), concave at the upper surface and convex on the lower. The jaws have 26–28 widely-spaced teeth on each side, being more strongly serrated on the back edge compared to the front.

    Its manus is large, having three strongly-curved claws similar in build and flexibility to modern birds' wings. The second digit is the longest, with the first being the shortest. The carpals prevented a pronated position, as in all dinosaurs. The first foot digit held a small dewclaw, as in all theropods. However, unusually to theropods but like other dromaeosaurs, the second digit is raised  and it only walked on the 3rd and 4rth digits. This modified digit bore a relatively large sickle claw, and could grow over 6.5 centimeters (2+1⁄2 inches) long around the outer edge. This was likely used during predation, probably used to tear up prey. Like in most dromaeosaurs, the prezygapophyses at the upper vertebral surfaces and ossified tendons have long, bony projections. It begins at the 10th caudal, extending to brace 4-10 more vertebrae, depending on how the tail sits. Once, these were thought to stiffen the tail as a single rod-like unit, but a specimen with a full caudal series curves in a sideways S-shape, suggesting the tail was more horizontally flexible than assumed. Quill knobs on the forearm of a *V. mongoliensis*, found in 2007, which confirmed the presence of feathers in *Velociraptor*. An adult *Velociraptor* could run a maximum of 64 km/h.

 File:Velociraptor vadarostrum.png

The specimen MPC-D 100/982, previously considered a *V. mongoliensis*, was found to be distinct enough from the others to be classified as a new species in 2021. It is going to be named "V. vadarostrum". The specimen is from the Flaming Cliffs locality, consisting of a nearly complete specimen differing from *V. mongoliensis* based on the following four features: an anteriorly abbreviated cerebellar fossa, an elongate olfactory canal, a lacrimal notch on the frontal that orients more vertically and a subvertical ridge on the ilium that sits anterodorsally to the acetabulum. These were previously considered individual variation, but no tests were performed. Nearly 15 linear measurements from eudromaeosaurs velociraptorine and non-velociraptorine to perform Principal Component Analysis, examining phenetic clustering in morphospace. This specimen falls well outside the variation, so much that it can be considered a new species. This is even greater than the variation observed in the *V. osmolskae* holotype. "V. vadarostrum" lived alongside *V. mongoliensis*. In 2021, the annual SVP abstracts mentioned multiple specimens assignable to this new species.

## Classification

*Velociraptor* is a eudromaeosaurian velociraptorine (the later most defined as "all dromaeosaurs more closely related to ***Velociraptor*** than to *Dromaeosaurus*"). Its subfamily was erected to only contain Velociraptor, but more genera have been included as of recent. *Deinonychus* and *Saurornitholestes* have historically been included in *Velociraptor*, previously named *V. antirrhopus* and *V. langstoni*. *Velociraptor* was first included in Megalosauridae upon naming, since it was once a wastebasket taxon. Sometimes, dromaeosaurs are seen as archaeopterygids, making them flightless birds by definition. Currie and Evans (2019) conclude the following, which is often seen as surprising (as *Achillobator* and *Utahraptor* are found as velociraptorines and the Bayan Shireh velociraptorine is seen as a dromaeosaurine):

## Paleobiology

### Feathers

Dromaeosaurids more primitive than *Velociraptor* show evidence of feathers and wings on their arms. Since their ancestors were feathered and possibly capable of flight and flightless birds retain their feathers, it has been suggested Velociraptor bore feathers as well. In September 2007, quill knobs from a *V. mongoliensis* forearm were found, indicating they bore wing feathers.

—Alan Turner

—Mark Norell
According to Turner, Norell and Peter Makovicky, state quill knobs are not present in all prehistoric birds, that their absence does not suggest a lack of feathers, like in flamingos, who have no quill knobs, but have feathers. Their presence, however, suggests modern wing feathers were present, with rachis and vane formed by barbs. The specimens preserving these, IGM 100/981, is an animal 1.5 meters (4 feet, 11 inches) long and 15 kilograms (33 pounds) heavy. 6 knobs are preserved in this specimen, suggesting it has 14 secondaries; compared with 12 (or more) seen in *Archaeopteryx*, 18 in *Microraptor* and 10 in *Rahonavis* This variation is expected, as it is seen in modern birds. Turner et al. interpret these as evidence that larger, flightless maniraptors lost their feathers secondarily due to their size. They also note the quill knobs are never seen in flightless species. Thus, they assume *Velociraptor* was flightless due to its short forelimbs and size, but presume its ancestors could fly, making it and other large dromaeosaurs secondarily flightless. However, the presumed large wing feathers in ancestors would have been for other purposes rather than flight. These retained wings may have been used for display, covering their nests during brooding, adding speed and thrust while running up inclined surfaces or "raptor prey restraint" (RPR).

### Feeding

The Fighting Dinosaurs, preserving *Velociraptor mongoliensis* and *Protoceratops andrewsi* locked in combat, were thought to have drowned in a flood upon discovery, but they were found in sand dune deposits. This specimen shows direct predatory behaviour. They likely died due to a collapsing dune or a sandstorm, and burial must have been quick, since they were buried and preserved in a lifelike, articulate pose. Parts of the *Protoceratops* are missing, finding evidence of scavenging from other animals. Comparisons of the sclerotic rings show *Velociraptor* may have been nocturnal, with *Protoceratops* being cathemeral, showing the fight likely occurred at twilight.

The sickle claw is typically depicted as a slashing weapon, used to disembowel prey. The Fighting Dinosaurs shows this claw embedded in the underside of its prey, while the prey clamps its forelimb in their beak. This suggests *Velociraptor* used these claws to target vitals, such as the jugular, carotid artery or trachea rather than the abdomen. This is further solidified by the claw's inside being rounded and not unusually sharp, showing such a slashing action was not possible. Additionally, the thick abdominal wall of large dinosaurs would have been difficult to completely slash through, but scatching its surface would have been easier. This was tested in The Truth About Killer Dinosaurs (2005), a documentary that used an artificial sickle claw and leg against a pork belly. The sickle penetrated the abdominal wall, but could not tear it open. This indicates it was not used to disembowel.

*Deinonychus* are often found in large groups and associated with *Tenontosaurus*, which has been used as evidence for pack hunting in *Velociraptor*. However, the only solid evidence for this is a Chinese trackway site showing 6 individuals of a large species moving together. Many specimens found are segregated, and not associated with others. Thus, the common depiction of *Velociraptor* as a pack hunter is not seen as credible to *Velociraptor* specifically, though some dromaeosaurs are thought to have done this. Few genera may have hunted in packs, but no evidence of this is present in *Velociraptor*.

Denver Fowler et al. (2011) suggested a new capture and restraint method for dromaeosaurs, known as "raptor prey restraint" (RPR), suggesting they killed like modern accipitrid birds of prey (leaping onto prey, restraining them under their weight and gripping them tightly with their curved claws. Like accipitrids, they suggested they would begin to feed upon their prey before death, and the prey would eventually die via blood loss and organ failure. They compare leg and feet morphology to extant birds who do this, finding they were most similar to eagles and hawks, especially with the enlarged second claw and grasping range. The short metatarsus and foot strength, however are most similar to owls. RPR fits *Velociraptor*'s anatomy, such as strange jaw and arm morphology; the former could exert a lot of force and had wings, likely used as flapping stabilizers to balance atop struggling prey with its stiff tail. Fowler et al. finds the jaws are comparatively, used for row saw motion bites like the Komodo dragon, to finish prey if kicks were not powerful enough. These may have been the origin for flapping in paraves.

Endocranial examinations indicate it could hear a range of 2368-3965 hertz, tracking prey with ease. This suggests it was an agile, swift predator. Evidence suggests Velociraptor scavenged, being opportunistic, but was an active predator. It ate carrion during drought or food shortage, if it were in poor health or depending on age.

Hone et al. (2010) found, based on a 2008 discovery, a shed tooth of cf. *Velociraptor* near a tooth-marked mandible of *Protoceratops* in the Bayan Mandahu Formation, finding it was a "late-stage carcass consumption by *Velociraptor*", since a predator would have targeted other areas before feeding upon the jaw, and that *Protoceratops* was a prey item because of the Fighting Dinosaurs specimen. Hone et al. (2012) found an azhdarchid long bone in the gut of a *Velociraptor*, which was interpreted as scavenging.

### Metabolism

*Velociraptor* was, to some degree, warm-blooded, requiring a significant amount of energy to hunt. Modern animals with feathery or furry integument tend to be warm-blooded, since they are used in insulation. However, bone growth rates in dromaeosaurs and some early birds show a moderate metabolism when compared with modern warm-blooded birds and mammals. Kiwi birds are similar to dromaeosaurs, anatomy wise; as in their feather type, bone structure and nasal passage anatomy reflecting their metabolism. Kiwis are active and specialized, with a stable body temperature and a (fairly) low metabolism. This makes it a good comparison for dromaeosaurs and primitive birds.

### Paleopathology

One *V. mongoliensis* skull has 2 parallel rows of small punctures matching the spacing and size of *Velociraptor* teeth. Thus, it is believed this was inflicted by another *Velociraptor* while fighting, showing no signs of healing around these wounds. It likely died because of such wounds. One specimen with azhdarchid remains in its gut preserves an injury in its ribs. It was recovering from or sustaining, with the azhdarchid bone devoid of pittinf or deformation from digestion, showing it died early after consumption, or possibly from the reported injury.

## Paleoecology

*V. mongoliensis* are recovered from the Djadochta (or Djadokhta) Formation of Ömnögovi, Mongolia, with other *Velociraptor* from the (slightly) younger Barun Goyot Formation, but are intermediate and may be an intermediate genus. These date to the Campanian (83-70 million years ago) of the Late Cretaceous. The type is from the Flaming Cliffs site, the Fighting Dinosaurs from Tugrig and Khulsan and Khermeen Tsav producing remains of Velociraptor or a related genus. Juvenile *V. mongoliensis* are reported from the Bayan Manadhu Formation. However, these have not been prepared or described yet (as of 2008). A partial skull from the same locality comprises *V. osmolskae*.

It lived in an arid environment with sand dune fields and intermittent streams, with the Barun Goyot seeming to be wetter than the Djadochta. The posture and preservation of any specimens show they were entombed alive during sandstorms or by collapsing dunes. In the Djadochta, V. mongoliensis lived with *Protoceratops andrewsi* and *Pinacosaurus grangeri*, with the Bayan Mandahu housing *V. osmolskae*, Protoceratops hellenikorhinus and *Pinacosaurus mephistocephalus* These species compositions may be due to a barrier separating these ecosystems, but since none are known and both are relatively close by, a slight time difference is suspected.

The *V. mongoliensis* locality includes *Saurornithoides*, *Mahakla* and *Oviraptor*. *V. osmolskae* lived with *Bagaceratops*, *Machairasaurus* and *Linheraptor*.

## Species

### Reassigned Species

* *V. antirrhopus*
* *V. langstoni*
* "V. nemegtensis"?

## Gallery

### Fossils

"V. vadarostrum"."V. vadarostrum".An undescribed *V. mongoliensis*.The *V. mongoliensis* type skull.*V. mongoliensis* from the Dueling Dinosaurs."V. vadarostrum".The type *V. mongoliensis* skull.
## References

1. ↑ https://era.library.ualberta.ca/items/c9c289c0-7cc4-42a0-ac53-9ffebf111d16/view/3c913f54-988b-40b8-8db2-f7ad9dee46e5/Powers\_Mark\_J\_202006\_MSc.pdf
2. ↑ 2.0 2.1 https://paleobiodb.org/classic/basicTaxonInfo?taxon\_no=54554
3. ↑ 3.0 3.1 3.2 3.3 3.4 3.5 3.6 https://en.wikipedia.org/wiki/Velociraptor
4. ↑ https://anatomypubs.onlinelibrary.wiley.com/doi/10.1002/ar.24241
5. ↑ S. Chao. 1980. Hsin-chiang pei pu chung sheng tai chi ch'ui tung wu hua shin ti ts'eng [Mesozoic vertebrate-bearing beds and stratigraphy of northern Xinjiang: report of the Paleontological Expedition to Xinjiang IV]. *Memoirs of the Institute of Vertebrate Paleontology and Paleoanthropology, Academia Sinica A* **15**:1-119 [M. Carrano/M. Carrano]
6. ↑ https://journals.library.ualberta.ca/vamp/index.php/VAMP/article/view/29374/21426
7. ↑ https://vertpaleo.org/wp-content/uploads/2021/10/SVP\_2021\_VirtualBook\_final.pdf
8. ↑ https://link.springer.com/article/10.1007%2Fs00114-013-1107-5
9. ↑ https://anatomypubs.onlinelibrary.wiley.com/doi/10.1002/ar.24241
10. ↑ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3237572