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.
"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 ability to fly or glide has been suggested for at least two dromaeosaur genera. The first, "Rahonavis" was originally classified as avian bird, but found to be a dromaeosaur in later studies. It may have been capable of powered flight. 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.
Dromaeosaurs share many features with early birds (clade Avialae or Aves). The nature of their relationship to birds is under discussion.
Mark Norell and colleagues analyzed a survey of coelurosaur fossils and suggested that dromaeosaurs were most closely related to birds, with troodontids as a more distant outgroup. In 2002, Hwang and colleagues suggested that birds (avialans) were better thought of as cousins to the dromaeosaurids and troodontids.
The current consensus among paleontologists agrees with Hwang that dromaeosaurids are most closely related to the troodontids, and together with the troodontids form the clade Deinonychosauria. Deinonychosaurians in turn are the sister taxon to avialans, and therefore the closest relatives of avialan birds.
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.
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. Xu and colleagues in 2003 cited the basal position of "Microraptor", along with feather and wing features, as evidence that the ancestral dromaeosaur could glide. In that case the larger dromaeosaurs would be secondarily terrestrial—having lost the ability to glide later in their evolutionary history.
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.
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.
The subfamilies of Dromaeosauridae is not yet settled. "Mahakala", for example, the most primitive dromaeosaur in terms of structure, falls outside any named sub-group. The most basal subfamily of dromaeosaurs is often found to be the Unenlagiinae.
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.
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).
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.
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