Dromaeosaur

* at Ottawa Museum]]
*.]]

**Dromaeosaurs** are a family of bird-like theropod dinosaurs. They include the famous *Velociraptor* and *Deinonychus*. They were small to medium-sized feathered carnivores which flourished in the Cretaceous period. 

They are often called **raptors**, a term popularized by the movie *Jurassic Park*. They were fast-running predators.

Dromaeosaurs eventually had a world-wide distribution. Isolated teeth suggest they first appeared in the Middle Jurassic, 167 million years ago (mya). But more complete records are not found before about 124 mya in the Lower Cretaceous. They spread to all continents. The group survived until the end of the Cretaceous, 65.5 mya at the K/T extinction event.

Although dromaeosaur teeth have been found in the Middle Jurassic, no dromaeosaurid body fossils have been found this early.

## Description
The Dromaeosaur skeleton suggests they were active, fast-running, and closely related to birds.

Dromaeosaurs have a relatively large skull,  teeth, narrow , and forward-facing eyes with some degree of binocular vision.

Dromaeosaurs, like most other theropods, had an S-curved neck, and their trunk was relatively short and deep. Like other maniraptorans, they had long arms, and relatively large hands with three long fingers ending in large claws.

The dromaeosaur hip structure featured a large 'pubic boot' (part of the hip) projecting beneath the base of the tail. These hip bones were places muscle and tendons attached.

Dromaeosaur feet bore a large, recurved claw on the second toe. Their tails were slender, and mainly used as a counterbalance. The enlarged second toe had an unusually large, curved sickle-shaped claw. It is thought to have been used in capturing prey and, in the smaller species, climbing trees.

One dromaeosaur species, *Balaur bondoc*, had a first toe which was modified to be in parallel with the second. Both the first and second toes on each foot of *B. bondoc* were also held retracted and bore enlarged, sickle-shaped claws.

### Tail
Dromaeosaurs had long tails. Most of the tail vertebrae bear bony, rod-like extensions, as well as bony tendons in some species. In his study of *Deinonychus*, Ostrom proposed that these features stiffened the tail so that it could only flex at the base, and the whole tail would then move as a single, rigid, lever. However, one well-preserved specimen of *Velociraptor mongoliensis* (IGM 100/986) has an articulated tail skeleton which is curved horizontally in an S-shape. This suggests that, in life, the tail could bend from side to side with some degree of flexibility. It has been proposed that this tail was used as a stabilizer and/or counterweight while running.

### Size 
Dromaeosaurs were small to medium-sized dinosaurs, ranging from about 0.7 meters in length (2.3&nbsp;ft, in the case of *Mahakala*) to over 6m (20&nbsp;ft, in *Utahraptor* and *Achillobator*). Some were larger: undescribed specimens of *Utahraptor* in the BYU collections may have been up to  long. Large size appears to have evolved at least twice among dromaeosaurs. A possible third lineage of giant dromaeosaurs is shown by isolated teeth on the Isle of Wight, England. The teeth belong to a *Utahraptor*-sized animal but are more similar in shape to the teeth of velociraptorines.

*Mahakala* is both the most primitive dromaeosaur ever described and the smallest. This evidence, fits with *Microraptor* and the troodontid *Anchiornis*. It suggests the common ancestor of dromaeosaurs, troodontids, and birds – the 'ancestral paravian' – may have been small, around 65&nbsp;cm in length and 600 to 700&nbsp;grams mass.

Many other dromaeosaur fossils have been found with feathers covering their bodies, some with fully-developed feathered wings. *Microraptor* even shows evidence of a second pair of wings on the hind legs.

## Paleobiology
### Claw function
There is some discussion about the function of the enlarged "sickle claw" on the second toe. When John Ostrom described it for *Deinonychus* in 1969, he interpreted the claw as a blade-like slashing weapon, much like the canines of some saber-toothed cats, used with powerful kicks to cut into prey. Adams (1987) suggested that the talon was used to disembowel large ceratopsian dinosaurs. The interpretation of the sickle claw as a killing weapon applied to all dromaeosaurs.

In Manning's interpretation, the second toe claw would be used as a climbing aid when subduing bigger prey and also as stabbing weapon.

Ostrom compared *Deinonychus* to the ostrich and cassowary. He noted that the bird species can inflict serious injury with the large claw on the second toe. The seriema also has an enlarged second toe claw, and uses it to tear apart small prey items for swallowing.

The Manning team also compared the curvature of the dromaeosarid "sickle claw" on the foot with curvature in modern birds and mammals. Previous studies had shown that the amount of curvature in a claw corresponded to what lifestyle the animal has: animals with strongly curved claws of a certain shape tend to be climbers, while straighter claws indicate ground-dwelling lifestyles. The sickle-claws of the dromaeosaurid *Deinonychus* have a curvature of 160 degrees, well within the range of climbing animals. The forelimb claws they studied also fell within the climbing range of curvature.

Paleontologist Peter Mackovicky said that small, primitive dromaeosaurids (such as *Microraptor*) were likely to have been tree-climbers, but that climbing did not explain why later, gigantic dromaeosaurids such as *Achillobator* retained highly curved claws when they were too large to have climbed trees.

### Group behavior
*Deinonychus* fossils have been uncovered in small groups near the remains of the herbivore *Tenontosaurus*, a larger ornithischian dinosaur. This had been interpreted as evidence that these dromaeosaurs hunted in coordinated packs like some modern mammals. However, not all paleontologists found the evidence conclusive, and a study in 2007 by Roach and Brinkman suggests that the *Deinonychus* may have actually displayed a disorganized mobbing behavior.

The first known extensive dromaeosaur trackway was found in Shandong, China.

The trackway, (made by a large, *Achillobator*-sized species), showed the sickle-claw was held off the ground. Six individuals of about equal size moved together along a shoreline. The individuals were spaced about one meter apart, and retained the same direction of travel, walking at a fairly slow pace. The trackways are evidence that some species of dromaeosaurs lived in groups. While the trackways clearly do not represent hunting behavior, the idea that groups of dromaeosaurs may have hunted together can not be ruled out. The forelimbs of *Rahonavis* were more powerfully built than *Archaeopteryx*, and show evidence that they bore strong ligament attachments necessary for flapping flight. Luis Chiappe concluded that, given these adaptations, *Rahonavis* could probably fly but would have been more clumsy in the air than modern birds.

Another species of dromaeosaur, *Microraptor*, may have been capable of gliding using its well-developed wings on both the fore and hind limbs. A 2005 study by Sankar Chatterjee suggested that the wings of *Microraptor* functioned like a split-level "biplane", and that it likely employed a style of gliding, in which it would launch from a perch and swoop downward in a 'U' shaped curve, then lift again to land on another tree, with the tail and hind wings helping to control its position and speed. Chatterjee also found that *Microraptor* had the basic requirements to sustain level powered flight in addition to gliding. In 2002, Hwang and colleagues suggested that birds (avialans) were better thought of as cousins to the dromaeosaurids and troodontids.

A consensus of paleontologists has concluded that there is not yet enough evidence to say whether any dromaeosaurs could fly or glide, or whether they evolved from ancestors that could.

#### Other ideas
At least two schools of researchers have proposed that dromaeosaurs may actually be descended from flying ancestors.

In 2002, Hwang *et al.* found that *Microraptor* was the most primitive dromaeosaur.

A few researchers, like Larry Martin, believe that dromaeosaurs, along with all maniraptorans are not dinosaurs at all. Martin asserted for decades that birds were unrelated to maniraptorans, but in 2004 he changed his position, and now he agrees that the two are the closest of relatives. Martin believes that maniraptorans are secondarily flightless birds, and that birds evolved from non–dinosaurian archosaurs, so that most of the species formerly called theropods would now not even be classified as dinosaurs.

A challenge to all of these alternative scenarios came when Turner and colleagues in 2007 described a new dromaeosaur, *Mahakala*, which they found to be the most basal and most primitive member of the Dromaeosauridae, more primitive than *Microraptor*.

*Mahakala* had short arms and no ability to glide. Turner *et al.* also inferred that flight evolved only in the Avialae, and these two points suggested that the ancestral dromaeosaurid could not glide or fly. Based on this cladistic analysis, *Mahakala* suggests that the ancestral condition for dromaeosaurids is non-flying.

### Phylogeny and taxonomy 
The family Dromaeosauridae was named in 1922, with only one new genus *Dromaeosaurus*. Dromaeosauridae, along with Troodontidae, make up the infraorder Deinonychosauria.

Dromaeosauridae was first defined as a clade by Paul Sereno in 1998, as the most inclusive natural group containing *Dromaeosaurus* but not *Troodon*, *Ornithomimus* or *Passer*. The various "subfamilies" have also been re-defined as clades.

All known dromaeosaur skin impressions come from this group, and all show an extensive covering of feathers and well-developed wings. Some species may have been capable of active flight.
*, a dromaeosaurine.]]
*, a microraptorine.]]

*, an unenlagiine.]]
The following classification of the various genera of dromaeosaurids is based on studies by Sereno (2005), Senter (2004), Makovicky *et al.* (2005), Norell *et al.* (2006), and Turner *et al.* (2007).
* **Family Dromaeosauridae**
** **Subfamily Dromaeosaurinae**
*** *Atrociraptor*
*** *Austroraptor*
*** *Buitreraptor*
*** *Neuquenraptor*
*** *Rahonavis*
*** *Unenlagia*
** **Subfamily Velociraptorinae** Velociraptorinae is a subfamily of the Dromaeosauridae. It existed from the Late Jurassic period to the end of the Cretaceous period. The Velociraptorinae consists of *Velociraptor*, *Deinonychus*, *Tsaagan*, *Saurornitholestes*, and *Balaur*. Teeth belonging to a giant velociraptorine the size of Utahraptor have also been reported from the Isle of Wight, England. In general, velociraptorines tend to have longer, narrower jaws and more slender bodily proportions than the dromaeosaurines.
*** *Adasaurus*
*** *Tsaagan*
*** *Velociraptor*

## In popular culture
A *Deinonychus'' appears in John Brosnan's 1984 novel *Carnosaur* and its movie adaptation though the book itself received little press attention.

*Velociraptor*, a dromaeosaur, got attention after it was featured in the 1993 Steven Spielberg movie *Jurassic Park*. However, the size of the *Velociraptor* in the movie is much larger than the largest members of that genus. Robert Bakker recalled that Spielberg had been disappointed with the dimensions of *Velociraptor* and so upsized it.

Michael Crichton used the name *Velociraptor* for the much larger raptor in his novels, on which the first two movies were based. The depiction of the dromaeosaur in the original *Jurassic Park* movie, while accurate for its time, is now known to have been inaccurate in some respects, such as the lack of feathers. While *Jurassic Park III* attempted to address this last oversight by adding quill-like structures around the head of some of its dromaeosaurs, they did not resemble the structure or distribution of actual dromaeosaurid feathers known from fossil remains.

Dromaeosaurids also appear in many of *The Land Before Time* movies, beginning with the third.

## References
## Other websites
* Dromaeosauridae  at DinoData.
* The Dromaeosauridae: The Raptors!, from the University of California Berkeley Museum of Paleontology.
* Dromaeosauridae , by Justin Tweet from *Thescelosaurus*.
* Dinosaurs – Complete and free online edition of the book "Dinosaurs" as written by W. D. Matthew (cited in this article with authorship of the family Dromaeosauridae), and former Curator of Vertebrate Paleontology at the American Museum of Natural History in New York; Originally published in 1915
* Dromaeosauridae , Dinosaur-world reference with in-depth description and pictures of many dromaeosauridae dinosaurs