Dromaeosauridae

Dromaeosauridae

Overview
Dromaeosauridae is a family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 of bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...

-like theropod dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...

s. They were small- to medium-sized feathered carnivore
Carnivore
A carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of animal tissue, whether through predation or scavenging...

s that flourished in the Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...

 Period. The name Dromaeosauridae means 'running lizards', from Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...

 dromeus (δρομευς) meaning 'runner' and sauros (σαυρος) meaning 'lizard'. In informal usage they are often called raptors (after Velociraptor
Velociraptor
Velociraptor is a genus of dromaeosaurid theropod dinosaur that existed approximately 75 to 71 million years ago during the later part of the Cretaceous Period. Two species are currently recognized, although others have been assigned in the past. The type species is V. mongoliensis; fossils...

), a term popularized by the film Jurassic Park
Jurassic Park (film)
Jurassic Park is a 1993 American science fiction adventure film directed by Steven Spielberg. The film is based on the novel of the same name by Michael Crichton. It stars Sam Neill, Laura Dern, Jeff Goldblum, Richard Attenborough, Martin Ferrero, and Bob Peck...

; a few types include the term "raptor" directly in their name and have come to emphasize their supposed bird-like habits.

Dromaeosaurid fossils have been found in North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

, Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

, Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...

, Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

, China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...

, Mongolia
Mongolia
Mongolia is a landlocked country in East and Central Asia. It is bordered by Russia to the north and China to the south, east and west. Although Mongolia does not share a border with Kazakhstan, its western-most point is only from Kazakhstan's eastern tip. Ulan Bator, the capital and largest...

, Madagascar
Madagascar
The Republic of Madagascar is an island country located in the Indian Ocean off the southeastern coast of Africa...

, Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...

, and Antarctica.
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Encyclopedia
Dromaeosauridae is a family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 of bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...

-like theropod dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...

s. They were small- to medium-sized feathered carnivore
Carnivore
A carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of animal tissue, whether through predation or scavenging...

s that flourished in the Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...

 Period. The name Dromaeosauridae means 'running lizards', from Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...

 dromeus (δρομευς) meaning 'runner' and sauros (σαυρος) meaning 'lizard'. In informal usage they are often called raptors (after Velociraptor
Velociraptor
Velociraptor is a genus of dromaeosaurid theropod dinosaur that existed approximately 75 to 71 million years ago during the later part of the Cretaceous Period. Two species are currently recognized, although others have been assigned in the past. The type species is V. mongoliensis; fossils...

), a term popularized by the film Jurassic Park
Jurassic Park (film)
Jurassic Park is a 1993 American science fiction adventure film directed by Steven Spielberg. The film is based on the novel of the same name by Michael Crichton. It stars Sam Neill, Laura Dern, Jeff Goldblum, Richard Attenborough, Martin Ferrero, and Bob Peck...

; a few types include the term "raptor" directly in their name and have come to emphasize their supposed bird-like habits.

Dromaeosaurid fossils have been found in North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

, Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

, Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...

, Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

, China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...

, Mongolia
Mongolia
Mongolia is a landlocked country in East and Central Asia. It is bordered by Russia to the north and China to the south, east and west. Although Mongolia does not share a border with Kazakhstan, its western-most point is only from Kazakhstan's eastern tip. Ulan Bator, the capital and largest...

, Madagascar
Madagascar
The Republic of Madagascar is an island country located in the Indian Ocean off the southeastern coast of Africa...

, Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...

, and Antarctica. They first appeared in the mid-Jurassic Period (late Bathonian
Bathonian
In the geologic timescale the Bathonian is an age or stage of the Middle Jurassic. It lasted from approximately 167.7 Ma to around 164.7 Ma...

 stage, about 164 million years ago) and survived until the end of the Cretaceous (Maastrichtian
Maastrichtian
The Maastrichtian is, in the ICS' geologic timescale, the latest age or upper stage of the Late Cretaceous epoch or Upper Cretaceous series, the Cretaceous period or system, and of the Mesozoic era or erathem. It spanned from 70.6 ± 0.6 Ma to 65.5 ± 0.3 Ma...

 stage, 65.5 ma), existing for over 100 million years, up until the Cretaceous–Paleogene extinction event. The presence of dromaeosaurs as early as the Middle Jurassic has been confirmed by the discovery of isolated fossil teeth, though no dromaeosaurid body fossils have been found from this period.

Description



The distinctive dromaeosaurid body plan
Body plan
A body plan is the blueprint for the way the body of an organism is laid out. An organism's symmetry, its number of body segments and number of limbs are all aspects of its body plan...

 helped to rekindle theories that at least some dinosaurs may have been active, fast, and closely related to birds. Robert Bakker’s illustration for John Ostrom
John Ostrom
John H. Ostrom was an American paleontologist who revolutionized modern understanding of dinosaurs in the 1960s, when he demonstrated that dinosaurs are more like big non-flying birds than they are like lizards , an idea first proposed by Thomas Henry Huxley in the 1860s, but which had garnered...

’s 1969 monograph, showing the dromaeosaurid Deinonychus
Deinonychus
Deinonychus was a genus of carnivorous dromaeosaurid dinosaur. There is one described species, Deinonychus antirrhopus. This 3.4 meter long dinosaur lived during the early Cretaceous Period, about 115–108 million years ago . Fossils have been recovered from the U.S...

in a fast run, is among the most influential paleontological reconstructions in history. The dromaeosaurid body plan includes a relatively large skull, serrated teeth, narrow snout, and forward-facing eyes which indicate some degree of binocular vision. Dromaeosaurids, like most other theropods, had a moderately long S-curved neck, and their trunk was relatively short and deep. Like other maniraptora
Maniraptora
Maniraptora is a clade of coelurosaurian dinosaurs which includes the birds and the dinosaurs that were more closely related to them than to Ornithomimus velox. It contains the major subgroups Avialae, Deinonychosauria, Oviraptorosauria and Therizinosauria. Ornitholestes and the Alvarezsauroidea...

ns, they had long arms that could be folded against the body in some species, and relatively large hands with three long fingers (the middle finger being the longest and the first finger being the shortest) ending in large claws. The dromaeosaurid hip structure featured a characteristically large pubic boot projecting beneath the base of the tail. Dromaeosaurid feet bore a large, recurved claw on the second toe. Their tails were slender, with long, low, vertebrae lacking transverse process and neural spines after the 14th caudal vertebra.

It is now known that at least some, and probably all, dromaeosaurids were covered in feathers, including large, vaned, wing and tail feathers. This development, first hypothesized in the mid-late 1980s and confirmed by fossil discoveries in 1999, represents a significant change in the way dromaeosaurids have historically been depicted in art and film (see “Feathers” below).

Foot


Like other theropods, dromaeosaurids were bipedal; that is, they walked on their hind legs. However, whereas most theropods walked with three toes contacting the ground, fossilized footprint tracks confirm that most deinonychosaurs
Deinonychosauria
The Deinonychosauria were a clade of coelurosaurian theropod dinosaurs from the Late Jurassic and Cretaceous periods. These omnivores and carnivores are known for their switchblade-like second toe claws and for displaying numerous bird-like characteristics. The clade has been divided into two...

, including the dromaeosaurids, held the second toe off the ground in a hyperextended position, with only the third and fourth toes bearing the weight of the animal. This is called functional didactyly. The enlarged second toe bore an unusually large, curved sickle-shaped claw (held off the ground or 'retracted' when walking), which is thought to have been used in capturing prey and climbing trees (see "Claw function" below). This claw was especially blade-like in the large-bodied predatory eudromaeosaurs
Eudromaeosauria
Eudromaeosauria is a subgroup of terrestrial dromaeosaurid theropod dinosaurs. They were relatively large-bodied, feathered hypercarnivores that flourished in the Cretaceous Period.Eudromaeosaur fossils are known almost exclusively from the northern hemisphere...

. One eudromaeosaur species, Balaur bondoc
Balaur (dinosaur)
Balaur is a uniquely specialized species of carnivorous dinosaur. It lived in what is now Romania during the latter part of the Late Cretaceous. Balaur was described by scientists in August 2010, and was named after the balaur, a dragon of Romanian folklore. It is known from a single partial...

, also possessed a first toe which was highly modified 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


Dromaeosaurids 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 that is curved horizontally in a long S-shape. This suggests that, in life, the tail could bend from side to side with a substantial degree of flexibility. It has been proposed that this tail was used as a stabilizer and/or counterweight while running or in the air; in Microraptor
Microraptor
Microraptor is a genus of small, four-winged dromaeosaurid dinosaurs. Numerous well-preserved fossil specimens have been recovered from Liaoning, China...

, an elongate diamond-shaped fan of feathers is preserved on the end of the tail. This may have been used as an aerodynamic stabilizer and rudder during gliding and/or powered flight (see "Flight and gliding" below).

Size



Dromaeosaurids were small to medium-sized dinosaurs, ranging from about 0.7 metres (2.3 ft) in length (in the case of Mahakala
Mahakala (dinosaur)
Mahakala is a genus of basal dromaeosaurid dinosaur from the Campanian-age Upper Cretaceous Djadokhta Formation of Ömnögov, Mongolia. It is based on a partial skeleton found in the Gobi Desert...

) to over 6 metres (19.7 ft) (in Utahraptor
Utahraptor
Utahraptor is a genus of theropod dinosaurs, including the largest known members of the family Dromaeosauridae. Fossil specimens date to the upper Barremian stage of the early Cretaceous period...

and Achillobator
Achillobator
Achillobator is a genus of dromaeosaurid theropod dinosaur from the late Cretaceous Period of what is now Mongolia, about 90 million years ago. It was probably an active bipedal predator, hunting with the large sickle-shaped claw on the second toe of each hind foot...

). Some may have grown larger; undescribed specimens of Utahraptor in Brigham Young University
Brigham Young University
Brigham Young University is a private university located in Provo, Utah. It is owned and operated by The Church of Jesus Christ of Latter-day Saints , and is the United States' largest religious university and third-largest private university.Approximately 98% of the university's 34,000 students...

 collections belonged to individuals that may have reached up to 11 m (36.1 ft) long, though these await more detailed study. Large size appears to have evolved at least twice among dromaeosaurids; once among the dromaeosaurines Utahraptor and Achillobator, and again among the unenlagiines (Austroraptor
Austroraptor
Austroraptor was a genus of dromaeosaurid dinosaur that lived about 70 million years ago during the Cretaceous period in what is now modern Argentina. The type species for the genus, Austroraptor cabazai, was described in late 2008 by Fernando Novas of the Museo Argentino de Ciencias Naturales...

, which measured 5 metres (16.4 ft) long). A possible third lineage of giant dromaeosaurs is represented by isolated teeth found on the Isle of Wight
Isle of Wight
The Isle of Wight is a county and the largest island of England, located in the English Channel, on average about 2–4 miles off the south coast of the county of Hampshire, separated from the mainland by a strait called the Solent...

, England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...

. The teeth belong to an animal the size of the dromaeosaurine Utahraptor
Utahraptor
Utahraptor is a genus of theropod dinosaurs, including the largest known members of the family Dromaeosauridae. Fossil specimens date to the upper Barremian stage of the early Cretaceous period...

, but they appear to belong to velociraptorines, judging by the shape of the teeth.

Mahakala is both the most primitive dromaeosaurid ever described and the smallest. This evidence, combined with the small size of other primitive relatives such as Microraptor and the troodontid
Troodontidae
Troodontidae is a family of bird-like theropod dinosaurs. During most of the 20th century, troodontid fossils were few and scrappy and they have therefore been allied, at various times, with many dinosaurian lineages...

 Anchiornis
Anchiornis
Anchiornis is a genus of small, feathered, deinonychosaurian dinosaur. The genus Anchiornis contains the type species Anchiornis huxleyi, named in honor of Thomas Henry Huxley, an early proponent of biological evolution, and the first to propose a close evolutionary relationship between birds and...

, indicates that the common ancestor of dromaeosaurids, troodontids, and birds – which is called the ancestral paravian
Paraves
Paraves is a branch-based clade containing birds and other closely related dinosaurs. The paravians include the Avialae, including Archaeopteryx and modern birds, and the Deinonychosauria, which includes the dromaeosaurids and troodontids....

 – may have been very small, at around 65 cm in length and 600 to 700 grams of mass.

Feathers




There is a large body of evidence showing that dromaeosaurids were covered in feather
Feather
Feathers are one of the epidermal growths that form the distinctive outer covering, or plumage, on birds and some non-avian theropod dinosaurs. They are considered the most complex integumentary structures found in vertebrates, and indeed a premier example of a complex evolutionary novelty. They...

s. Some dromaeosaurid fossils preserve long, pennaceous feathers on the hands and arms (remiges) and tail (rectrices), as well as shorter, down-like feathers covering the body. Other fossils, which do not preserve actual impressions of feathers, still preserve the associated bumps on the forearm bones where long wing feathers would have attached in life. Overall, this feather pattern looks very much like Archaeopteryx
Archaeopteryx
Archaeopteryx , sometimes referred to by its German name Urvogel , is a genus of theropod dinosaur that is closely related to birds. The name derives from the Ancient Greek meaning "ancient", and , meaning "feather" or "wing"...

.

The first known dromaeosaur with definitive evidence of feather
Feather
Feathers are one of the epidermal growths that form the distinctive outer covering, or plumage, on birds and some non-avian theropod dinosaurs. They are considered the most complex integumentary structures found in vertebrates, and indeed a premier example of a complex evolutionary novelty. They...

s was Sinornithosaurus
Sinornithosaurus
Sinornithosaurus is a genus of feathered dromaeosaurid dinosaur from the early Cretaceous Period of the Yixian Formation in what is now China. It was the fifth non–avian feathered dinosaur genus discovered by 1999...

, reported from China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...

 by Xu et al. in 1999. Many other dromaeosaurid fossils have been found with feathers covering their bodies, some with fully developed feathered wings. Microraptor
Microraptor
Microraptor is a genus of small, four-winged dromaeosaurid dinosaurs. Numerous well-preserved fossil specimens have been recovered from Liaoning, China...

even shows evidence of a second pair of wings on the hind legs. While direct feather impressions are only possible in fine-grained sediments, some fossils found in coarser rocks show evidence of feathers by the presence of quill knobs, the attachment points for wing feathers possessed by some birds. The dromaeosaurids Rahonavis and Velociraptor have both been found with quill knobs, showing that these forms had feathers despite no impressions having been found. In light of this, it is most likely that even the larger ground-dwelling dromaeosaurids bore feathers, since even flightless birds today retain most of their plumage, and relatively large dromaeosaurids, like Velociraptor, are known to have retained pennaceous feathers. Though some scientists had suggested that the larger dromaeosaurids lost some or all of their insulatory covering, the discovery of feathers in Velociraptor specimens has been cited as evidence that all members of the family retained feathers.

Claw function



There is currently disagreement 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
Homotherium
Homotherium is an extinct genus of machairodontine saber-toothed cats, often termed scimitar cats, endemic to North America, South America, Europe, Asia, and Africa during the Pliocene and Pleistocene epochs , existing for approximately .It first became extinct in Africa some 1.5 million years ago...

, 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 dromaeosaurids. However, Manning et al. argued that the claw instead served as a hook, reconstructing the keratinous sheath with an elliptical cross section, instead of the previously inferred inverted teardrop shape. 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
Ostrich
The Ostrich is one or two species of large flightless birds native to Africa, the only living member of the genus Struthio. Some analyses indicate that the Somali Ostrich may be better considered a full species apart from the Common Ostrich, but most taxonomists consider it to be a...

 and cassowary
Cassowary
The cassowaries are ratites, very large flightless birds in the genus Casuarius native to the tropical forests of New Guinea, nearby islands and northeastern Australia. There are three extant species recognized today...

. He noted that the bird species can inflict serious injury with the large claw on the second toe. The cassowary
Cassowary
The cassowaries are ratites, very large flightless birds in the genus Casuarius native to the tropical forests of New Guinea, nearby islands and northeastern Australia. There are three extant species recognized today...

 has claws up to 125 millimetres (4.9 in) long. Ostrom cited Gilliard (1958) in saying that they can sever an arm or disembowel a man. Kofron (1999 and 2003) studied 241 documented cassowary attacks and found that one human and two dogs had been killed, but no evidence that cassowaries
Cassowary
The cassowaries are ratites, very large flightless birds in the genus Casuarius native to the tropical forests of New Guinea, nearby islands and northeastern Australia. There are three extant species recognized today...

 can disembowel or dismember other animals. Cassowaries
Cassowary
The cassowaries are ratites, very large flightless birds in the genus Casuarius native to the tropical forests of New Guinea, nearby islands and northeastern Australia. There are three extant species recognized today...

 use their claws to defend themselves, to attack threatening animals, and in agonistic displays such as the Bowed Threat Display. The seriema
Seriema
The seriemas are the sole extant members of the small and ancient family Cariamidae, which is also the sole surviving family of the Cariamae. Once believed to be related to cranes, they have been placed by one recent study near the falcons, parrots and passerines, as well as the extinct terror birds...

 also has an enlarged second toe claw, and uses it to tear apart small prey items for swallowing.

Phillip Manning and colleagues (2009) attempted to test the function of the sickle claw and similarly shaped claws on the forelimbs. They analyzed the bio-mechanics of how stresses and strains would be distributed along the claws and into the limbs, using X-ray imaging to create a three dimensional contour map of a forelimb claw from Velociraptor
Velociraptor
Velociraptor is a genus of dromaeosaurid theropod dinosaur that existed approximately 75 to 71 million years ago during the later part of the Cretaceous Period. Two species are currently recognized, although others have been assigned in the past. The type species is V. mongoliensis; fossils...

. For comparison, they analyzed the construction of a claw from a modern predatory bird, the Eagle Owl. They found that, based on the way that stress was conducted along the claw, they were ideal for climbing. The scientists found that the sharpened tip of the claw was a puncturing and gripping instrument, while the curved and expanded claw base helped transfer stress loads evenly.

The Manning team also compared the curvature of the dromaeosaurid "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 commented on the Manning team's study, stating that small, primitive dromaeosaurids (such as Microraptor
Microraptor
Microraptor is a genus of small, four-winged dromaeosaurid dinosaurs. Numerous well-preserved fossil specimens have been recovered from Liaoning, China...

) were likely to have been tree-climbers, but that climbing did not explain why later, gigantic dromaeosaurids such as Achillobator
Achillobator
Achillobator is a genus of dromaeosaurid theropod dinosaur from the late Cretaceous Period of what is now Mongolia, about 90 million years ago. It was probably an active bipedal predator, hunting with the large sickle-shaped claw on the second toe of each hind foot...

retained highly curved claws when they were too large to have climbed trees. Mackovickey speculated that giant dromaeosaurids may have adapted the claw to be used exclusively for latching on to prey.

In 2009 Phil Senter published a study on dromaeosaurid toes and showed that their range of motion was compatible with the excavation of tough insect nests. Senter suggested that small dromaeosaurids such as Rahonavis
Rahonavis
Rahonavis is a genus of bird-like dinosaur from the Late Cretaceous of what is now northwestern Madagascar. It is known from a partial skeleton found in Maevarano Formation rocks at a quarry near Berivotra, Mahajanga Province...

and Buitreraptor
Buitreraptor
Buitreraptor is a predatory dromaeosaurid theropod dinosaur from the Cretaceous of Argentina.Buitreraptor was described in 2005. The type species is Buitreraptor gonzalezorum...

were small enough to be partial insectivore
Insectivore
An insectivore is a type of carnivore with a diet that consists chiefly of insects and similar small creatures. An alternate term is entomophage, which also refers to the human practice of eating insects....

s, while larger genera such as Deinonychus
Deinonychus
Deinonychus was a genus of carnivorous dromaeosaurid dinosaur. There is one described species, Deinonychus antirrhopus. This 3.4 meter long dinosaur lived during the early Cretaceous Period, about 115–108 million years ago . Fossils have been recovered from the U.S...

and Neuquenraptor
Neuquenraptor
Neuquenraptor is a dromaeosaurid theropod dinosaur of the Late Cretaceous of Argentina, one of the first dromaeosaurids found in the Southern Hemisphere....

could have used this ability to catch vertebrate
Vertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...

 prey residing in insect nests. However, Senter did not test whether the strong curvature of dromaeosaurid claws was also conductive to such activities.

Group behavior



Deinonychus
Deinonychus
Deinonychus was a genus of carnivorous dromaeosaurid dinosaur. There is one described species, Deinonychus antirrhopus. This 3.4 meter long dinosaur lived during the early Cretaceous Period, about 115–108 million years ago . Fossils have been recovered from the U.S...

fossils have been uncovered in small groups near the remains of the herbivore Tenontosaurus
Tenontosaurus
Tenontosaurus is a genus of medium- to large-sized ornithopod dinosaur. The genus is known from the late Aptian to Albian ages of the middle Cretaceous period sediments of western North America, dating between 115 to 108 million years ago...

, a larger ornithischia
Ornithischia
Ornithischia or Predentata is an extinct order of beaked, herbivorous dinosaurs. The name ornithischia is derived from the Greek ornitheos meaning 'of a bird' and ischion meaning 'hip joint'...

n dinosaur. This had been interpreted as evidence that these dromaeosaurs hunted in coordinated packs like some modern mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...

s. However, not all paleontologists found the evidence conclusive, and a subsequent study published in 2007 by Roach and Brinkman suggests that the Deinonychus may have actually displayed a disorganized mobbing behavior. Modern diapsid
Diapsid
Diapsids are a group of reptiles that developed two holes in each side of their skulls, about 300 million years ago during the late Carboniferous period. Living diapsids are extremely diverse, and include all crocodiles, lizards, snakes, and tuatara...

s, including bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...

s and crocodile
Crocodile
A crocodile is any species belonging to the family Crocodylidae . The term can also be used more loosely to include all extant members of the order Crocodilia: i.e...

s (the closest relatives of dromaeosaurs), display minimal cooperative hunting; instead, they are usually either solitary hunters, or are drawn to previously killed carcasses, where conflict often occurs between individuals of the same species. For example, in situations where groups of komodo dragon
Komodo dragon
The Komodo dragon , also known as the Komodo monitor, is a large species of lizard found in the Indonesian islands of Komodo, Rinca, Flores, Gili Motang and Gili Dasami. A member of the monitor lizard family , it is the largest living species of lizard, growing to a maximum length of in rare cases...

s are eating together, the largest individuals eat first and might attack smaller komodo dragons that attempt to feed; if the smaller animal dies, it is usually cannibalized
Cannibalism (zoology)
In zoology, cannibalism is the act of one individual of a species consuming all or part of another individual of the same species as food. Cannibalism is a common ecological interaction in the animal kingdom and has been recorded for more than 1500 species...

. When this information is applied to the sites containing putative pack-hunting behavior in dromaeosaurs, it appears somewhat consistent with a komodo- or crocodile-like feeding strategy. Deinonychus skeletal remains found at these sites are from subadults, with missing parts that may have been eaten by other Deinonychus, which a study by Roach et al. presented as evidence against the idea that the animals cooperated in the hunt.

In 2007, scientists described the first known extensive dromaeosaur trackway
Fossil trackway
A fossil trackway is a type of trace fossil, a trackway made by an organism. Many fossil trackways were made by dinosaurs, early tetrapods, and other quadrupeds and bipeds on land...

, in Shandong, China. In addition to confirming the hypothesis that the sickle-claw was held retracted off the ground, the trackway (made by a large, Achillobator
Achillobator
Achillobator is a genus of dromaeosaurid theropod dinosaur from the late Cretaceous Period of what is now Mongolia, about 90 million years ago. It was probably an active bipedal predator, hunting with the large sickle-shaped claw on the second toe of each hind foot...

-sized species) showed evidence of six individuals of about equal size moving 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 authors of the paper describing these footprints interpreted the trackways as 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 could not be ruled out.

Flying and gliding



The ability to fly or glide
Flying and gliding animals
A number of animals have evolved aerial locomotion, either by powered flight or by gliding. Flying and gliding animals have evolved separately many times, without any single ancestor. Flight has evolved at least four times, in the insects, pterosaurs, birds, and bats. Gliding has evolved on many...

 has been suggested for at least two dromaeosaurid species. The first, Rahonavis ostromi
Rahonavis
Rahonavis is a genus of bird-like dinosaur from the Late Cretaceous of what is now northwestern Madagascar. It is known from a partial skeleton found in Maevarano Formation rocks at a quarry near Berivotra, Mahajanga Province...

(originally classified as avian bird, but found to be a dromaeosaurid in later studies) may have been capable of powered flight
Flight
Flight is the process by which an object moves either through an atmosphere or beyond it by generating lift or propulsive thrust, or aerostatically using buoyancy, or by simple ballistic movement....

, as indicated by its long forelimbs with evidence of quill knob attachments for long sturdy flight feathers. 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 dromaeosaurid, Microraptor gui
Microraptor
Microraptor is a genus of small, four-winged dromaeosaurid dinosaurs. Numerous well-preserved fossil specimens have been recovered from Liaoning, China...

, may have been capable of gliding using its well-developed wings on both the fore and hind limbs. A 2005 study by Sankar Chatterjee
Sankar Chatterjee
Sankar Chatterjee is a paleontologist, and is the Paul W. Horn Professor of Geosciences at Texas Tech University and Curator of Paleontology at the Museum of Texas Tech University. He earned his Ph. D. from the University of Calcutta in 1970 and was a Post-doctoral Fellow at the Smithsonian...

 suggested that the wings of Microraptor functioned like a split-level "biplane
Biplane
A biplane is a fixed-wing aircraft with two superimposed main wings. The Wright brothers' Wright Flyer used a biplane design, as did most aircraft in the early years of aviation. While a biplane wing structure has a structural advantage, it produces more drag than a similar monoplane wing...

", and that it likely employed a phugoid
Phugoid
A phugoid or fugoid is an aircraft motion where the vehicle pitches up and climbs, and then pitches down and descends, accompanied by speeding up and slowing down as it goes "uphill" and "downhill." This is one of the basic flight dynamics modes of an aircraft , and a classic example of a positive...

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.

Powered flight has also been suggested for the species Cryptovolans pauli (the name of which means "hidden flyer"), though Cryptovolans is probably synonymous with Microraptor.

Senses


Comparisons between the scleral ring
Sclerotic ring
Sclerotic rings are rings of bone found in the eyes of several groups of vertebrate animals, except for mammals and crocodilians. They can be made up of single bones or small bones together. They are believed to have a role in supporting the eye, especially in animals whose eyes are not spherical,...

s of several dromaeosaurids (Microraptor
Microraptor
Microraptor is a genus of small, four-winged dromaeosaurid dinosaurs. Numerous well-preserved fossil specimens have been recovered from Liaoning, China...

, Sinornithosaurus
Sinornithosaurus
Sinornithosaurus is a genus of feathered dromaeosaurid dinosaur from the early Cretaceous Period of the Yixian Formation in what is now China. It was the fifth non–avian feathered dinosaur genus discovered by 1999...

, and Velociraptor
Velociraptor
Velociraptor is a genus of dromaeosaurid theropod dinosaur that existed approximately 75 to 71 million years ago during the later part of the Cretaceous Period. Two species are currently recognized, although others have been assigned in the past. The type species is V. mongoliensis; fossils...

) and modern birds and reptiles indicate that some dromaeosaurids (including Microraptor and Velociraptor) may have been nocturnal predators, while Sinornithosaurus is inferred to be cathemeral
Cathemeral
A cathemeral organism is one that has sporadic and random intervals of activity during the day or night in which food is acquired, socializing with other organisms occurs, and any other activities necessary for livelihood are performed...

 (active throughout the day at short intervals).

Studies of the olfactory bulb
Olfactory bulb
The olfactory bulb is a structure of the vertebrate forebrain involved in olfaction, the perception of odors.-Anatomy:In most vertebrates, the olfactory bulb is the most rostral part of the brain. In humans, however, the olfactory bulb is on the inferior side of the brain...

s of dromaeosaurids reveal that they had similar olfactory ratios for their size to other non-avian theropods and modern birds with an acute sense of smell, such as tyrannosaurid
Tyrannosauridae
Tyrannosauridae is a family of coelurosaurian theropod dinosaurs which comprises two subfamilies containing up to six genera, including the eponymous Tyrannosaurus. The exact number of genera is controversial, with some experts recognizing as few as three...

s and the Turkey Vulture
Turkey Vulture
The Turkey Vulture is a bird found throughout most of the Americas. It is also known in some North American regions as the Turkey Buzzard , and in some areas of the Caribbean as the John Crow or Carrion Crow...

, probably reflecting the importance of the olfactory sense in the daily activities of dromaeosaurids such as finding food.

Paleopathology


In 2001, Bruce Rothschild and others published a study examining evidence for stress fractures and tendon avulsions in theropod dinosaurs and the implications for their behavior. Since stress fractures are caused by repeated trauma rather than singular events they are more likely to be caused by regular behavior than other types of injuries. The researchers found lesion like those caused by stress fractures on a dromaeosaurid hand claw, one of only two such claw lesions discovered in the course of the study. Stress fractures in the hands have special behavioral significance compared to those found in the feet since stress fractures there can be obtained while running or during migration. Hand injuries, by contrast, are more likely to be obtained while in contact with struggling prey.

Relationship with birds




Dromaeosaurids share many features with early bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...

s (clade Avialae
Avialae
Avialae is a clade of dinosaurs containing their only living representatives, birds , and the most immediate extinct relatives of birds.-Competing definitions:...

 or Aves). The precise nature of their relationship to birds has undergone a great deal of study, and hypotheses about that relationship have changed as large amounts of new evidence became available. As late as 2001, Mark Norell and colleagues analyzed a large survey of coelurosaur fossils and produced the tentative result that dromaeosaurids were most closely related to birds, with troodontids as a more distant outgroup. They even suggested that Dromaeosauridae could be paraphyletic relative to Avialae. In 2002, Hwang and colleagues utilized the work of Norell et al., including new characters and better fossil evidence, to determine that birds (avialans) were better thought of as cousins to the dromaeosaurids and troodontids.

The current consensus among paleontologists agrees with the findings of Hwang et al. (2002); that dromaeosaurids are most closely related to the troodontids, and together with the troodontids form the clade Deinonychosauria
Deinonychosauria
The Deinonychosauria were a clade of coelurosaurian theropod dinosaurs from the Late Jurassic and Cretaceous periods. These omnivores and carnivores are known for their switchblade-like second toe claws and for displaying numerous bird-like characteristics. The clade has been divided into two...

. 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 determine whether any dromaeosaurs could fly or glide, or whether they evolved from ancestors that could.

Alternative theories and flightlessness


Dromaeosaurids are so birdlike that they have led some researchers to argue that they would be better classified as birds. First, since they had feathers, dromaeosaurs (along with many other coelurosaurian theropod dinosaurs) are “birds” under traditional definitions of the word “bird”, or “Aves”, that are based on the possession of feathers. However, other scientists, such as Lawrence Witmer, have argued that calling a theropod like Caudipteryx
Caudipteryx
Caudipteryx is a genus of peacock-sized theropod dinosaurs that lived in the Aptian age of the early Cretaceous Period . They were feathered and remarkably birdlike in their overall appearance....

a bird because it has feathers may stretch the word past any useful meaning. (See the article Avialae
Avialae
Avialae is a clade of dinosaurs containing their only living representatives, birds , and the most immediate extinct relatives of birds.-Competing definitions:...

 for a discussion about the definitions of the clades Aves and Avialae.)

At least two schools of researchers have proposed that dromaeosaurs may actually be descended from flying ancestors. Hypotheses involving a flying ancestor for dromaeosaurs are sometimes called “Birds Came First” (BCF). George Olshevsky
George Olshevsky
George Olshevsky is a freelance editor, writer, publisher, amateur paleontologist, and mathematician living in San Diego, California.Olshevsky maintains the comprehensive online Dinosaur Genera List...

 is usually credited as the first author of BCF. In his own work, Gregory S. Paul pointed out numerous features of the dromaeosaurid skeleton that he interpreted as evidence that the entire group had evolved from flying, dinosaurian, ancestors, perhaps something like Archaeopteryx
Archaeopteryx
Archaeopteryx , sometimes referred to by its German name Urvogel , is a genus of theropod dinosaur that is closely related to birds. The name derives from the Ancient Greek meaning "ancient", and , meaning "feather" or "wing"...

. In that case, the larger dromaeosaurids were secondarily flightless, like the modern ostrich
Ostrich
The Ostrich is one or two species of large flightless birds native to Africa, the only living member of the genus Struthio. Some analyses indicate that the Somali Ostrich may be better considered a full species apart from the Common Ostrich, but most taxonomists consider it to be a...

. In 1988, Paul suggested that dromaeosaurids may actually be more closely related to modern birds than to Archaeopteryx. By 2002, however, Paul placed dromaeosaurs and Archaeopteryx as the closest relatives to one another.

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.

Also in 2002, Steven Czerkas described Cryptovolans, though it is a probable junior synonym of Microraptor
Microraptor
Microraptor is a genus of small, four-winged dromaeosaurid dinosaurs. Numerous well-preserved fossil specimens have been recovered from Liaoning, China...

. He reconstructed the fossil inaccurately with only two wings and thus argued that dromaeosaurs were proper birds, rather than possible gliders. He later issued a revised reconstruction in agreement with that of Microraptor
Microraptor
Microraptor is a genus of small, four-winged dromaeosaurid dinosaurs. Numerous well-preserved fossil specimens have been recovered from Liaoning, China...



Other researchers, like Larry Martin
Larry Martin
Larry Martin is an American vertebrate paleontologist and curator of the Natural History Museum and Biodiversity Research Center at the University of Kansas. Among Martin's work is research on the Triassic reptile Longisquama and theropod dinosaur Caudipteryx...

 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.

In 2005, Mayr and Peters described the anatomy of a very well preserved specimen of Archaeopteryx, and determined that its anatomy was more like non-avian theropods than previously understood. Specifically, they found that Archaeopteryx had a primitive palatine, unreversed hallux, and hyper-extendable second toe. Their phylogenetic analysis produced the controversial result that Confuciusornis
Confuciusornis
Confuciusornis is a genus of primitive crow-sized birds from the Early Cretaceous Yixian and Jiufotang Formations of China, dating from 125 to 120 million years ago...

was closer to Microraptor than to Archaeopteryx, making the Avialae a paraphyletic taxon. They also suggested that the ancestral paravian was able to fly or glide, and that the dromaeosaurs and troodontids were secondarily flightless (or had lost the ability to glide). Corfe and Butler criticized this work on methodological grounds.

A challenge to all of these alternative scenarios came when Turner and colleagues in 2007 described a new dromaeosaurid, Mahakala
Mahakala (dinosaur)
Mahakala is a genus of basal dromaeosaurid dinosaur from the Campanian-age Upper Cretaceous Djadokhta Formation of Ömnögov, Mongolia. It is based on a partial skeleton found in the Gobi Desert...

, 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-volant
Flight
Flight is the process by which an object moves either through an atmosphere or beyond it by generating lift or propulsive thrust, or aerostatically using buoyancy, or by simple ballistic movement....

.

Taxonomy


The authorship of the family Dromaeosauridae is credited to William Diller Matthew
William Diller Matthew
William Diller Matthew FRS was a vertebrate paleontologist who worked primarily on mammal fossils....

 and Barnum Brown
Barnum Brown
Barnum Brown , a paleontologist born in Carbondale, Kansas, and named after the circus showman P.T. Barnum, discovered the second fossil of Tyrannosaurus rex during a career that made him one of the most famous fossil hunters working from the late Victorian era into the early 20th century.Sponsored...

, who erected it as a subfamily (Dromaeosaurinae) of the family Deinodontidae in 1922, containing only the new genus Dromaeosaurus
Dromaeosaurus
Dromaeosaurus was a genus of theropod dinosaur which lived during the Late Cretaceous period , sometime between 76.5 and 74.8 million years ago, in the western United States and Alberta, Canada. The name means 'running lizard'....

. Dromaeosauridae, along with Troodontidae
Troodontidae
Troodontidae is a family of bird-like theropod dinosaurs. During most of the 20th century, troodontid fossils were few and scrappy and they have therefore been allied, at various times, with many dinosaurian lineages...

, make up the infraorder Deinonychosauria
Deinonychosauria
The Deinonychosauria were a clade of coelurosaurian theropod dinosaurs from the Late Jurassic and Cretaceous periods. These omnivores and carnivores are known for their switchblade-like second toe claws and for displaying numerous bird-like characteristics. The clade has been divided into two...

.

The subfamilies of Dromaeosauridae frequently shift in content based on new analysis, but typically consist of the following groups. A number of dromaeosaurids have not been assigned to any particular subfamily, often because they are too poorly preserved to be placed confidently in phylogenetic analysis (see section Phylogeny below), or because they are basal relative to the primary subdivisions of Dromaeosauridae (Mahakala
Mahakala (dinosaur)
Mahakala is a genus of basal dromaeosaurid dinosaur from the Campanian-age Upper Cretaceous Djadokhta Formation of Ömnögov, Mongolia. It is based on a partial skeleton found in the Gobi Desert...

, for example, is the most primitive known dromaeosaurid and falls outside any named sub-group). The most basal subfamily of dromaeosaurids is often found to be the Unenlagiinae. This enigmatic group is the most poorly supported subfamily of dromaeosaurs and it is possible that some or all of its members belong outside of Dromaeosauridae. The larger, ground-dwelling members like Buitreraptor
Buitreraptor
Buitreraptor is a predatory dromaeosaurid theropod dinosaur from the Cretaceous of Argentina.Buitreraptor was described in 2005. The type species is Buitreraptor gonzalezorum...

and Unenlagia
Unenlagia
Unenlagia is a genus of, possibly dromaeosaurid, theropod dinosaur from the Late Cretaceous of Argentina....

show strong flight adaptations, although they were probably too large to 'take off'. One member of this group, Rahonavis, is very small, with well-developed wings that show evidence of quill knobs (the attachment points for flight feathers) and it is very likely that it could fly. The next most primitive clade of dromaeosaurs is the Microraptoria. This group includes many of the smallest dromaeosaurs, which show adaptations for living in trees. All known dromaeosaur skin impressions hail from this group and all show an extensive covering of feathers and well-developed wings. Like the unenlagiines, some species may have been capable of active flight. The subfamily Velociraptorinae has traditionally included Velociraptor, Deinonychus
Deinonychus
Deinonychus was a genus of carnivorous dromaeosaurid dinosaur. There is one described species, Deinonychus antirrhopus. This 3.4 meter long dinosaur lived during the early Cretaceous Period, about 115–108 million years ago . Fossils have been recovered from the U.S...

, and Saurornitholestes
Saurornitholestes
Saurornitholestes is a genus of carnivorous dromaeosaurid theropod dinosaur from the late Cretaceous of Alberta, Montana and New Mexico....

, and while the discovery of Tsaagan
Tsaagan
Tsaagan is a genus of carnivorous dromaeosaurid theropod dinosaur from the Djadokhta Formation of the late Cretaceous of Mongolia....

lent support to this grouping, the inclusion of Saurornitholestes is still uncertain. The Dromaeosaurinae is usually found to consist of medium to giant-sized species, with generally box-shaped skulls (the other subfamilies generally have narrower snouts).


The following classification of the various genera of dromaeosaurids follows the table provided in Holtz, 2010 unless otherwise noted.
  • Family Dromaeosauridae
    • Dromaeosauroides
      Dromaeosauroides
      Dromaeosauroides is a genus of dromaeosaurid theropod dinosaur from the Early Cretaceous of Denmark.In the southwest of the island of Bornholm, layers of the Early Cretaceous Jydegaard Formation surface, dating to the late Berriasian age, about 140 million years ago and consisting of marine...

    • Luanchuanraptor
      Luanchuanraptor
      Luanchuanraptor is a genus of dromaeosaurid theropod dinosaur from the Late Cretaceous of China. It is based on a partial skeleton from the Qiupa Formation in Luanchuan, Henan. A medium-sized dromaeosaurid, it is the first Asian dromaeosaurid described from outside the Gobi Desert or northeastern...

    • Mahakala
      Mahakala (dinosaur)
      Mahakala is a genus of basal dromaeosaurid dinosaur from the Campanian-age Upper Cretaceous Djadokhta Formation of Ömnögov, Mongolia. It is based on a partial skeleton found in the Gobi Desert...

    • Pamparaptor
      Pamparaptor
      Pamparaptor is an extinct genus of carnivorous deinonychosaur from the late Cretaceous period. It is a basal dromaeosaurid with troodontid-like pes which lived during the late Cretaceous period in what is now Neuquén province, Patagonia, Argentina. It is known from the holotype MUCPv-1163, an...

    • Ornithodesmus
      Ornithodesmus
      Ornithodesmus is a genus of small, deinonychosaurian dinosaur from the Isle of Wight in England, dating to about 125 million years ago. The name was originally assigned to a bird-like sacrum , initially believed to come from a pterosaur...

    • Tianyuraptor
      Tianyuraptor
      Tianyuraptor is a genus of short-armed dromaeosaurid dinosaur that lived during the Early Cretaceous, about 122 million years ago. Its remains have been found in western Liaoning, China. It was similar to other dromaeosaurids found in Liaoning, with the exception of being somewhat more primitive...

    • Variraptor
      Variraptor
      Variraptor is a genus of coelurosaurian theropod dinosaur from the Late Cretaceous of France.Between 1992 and 1995 amateur paleontologists Patrick Méchin and Annie Méchin-Salessy uncovered the remains of a small theropod in the Grès à Reptiles Formation at La Bastide Neuve, near Fox-Amphoux...

      (=Pyroraptor
      Pyroraptor
      Pyroraptor is a genus of dromaeosaurid dinosaur from the late Cretaceous Period of France. It is known from a single specimen. It was found in 1992 in the south of France, in Provence, and is known only from a few bones. It was named Pyroraptor olympius by Allain and Taquet in 2000. The name means...

      ?)
    • Subfamily Microraptorinae
      Microraptorinae
      Microraptorinae is a subfamily of Dromaeosauridae. Microraptorines were among the most primitive dromaeosaurids. They appeared 125 million years ago in China. Many may have been semi-arboreal gliders...

      • Graciliraptor
        Graciliraptor
        Graciliraptor is a genus of theropod dinosaur from the early Cretaceous Period. It is a microraptorine dromaeosaurid....

      • Hesperonychus
        Hesperonychus
        Hesperonychus was a genus of small, carnivorous dromaeosaurid dinosaur. There is one described species, Hesperonychus elizabethae; the type species was named in honor of the woman who collected it in 1982...

      • Microraptor
        Microraptor
        Microraptor is a genus of small, four-winged dromaeosaurid dinosaurs. Numerous well-preserved fossil specimens have been recovered from Liaoning, China...

        (=Cryptovolans?)
      • Sinornithosaurus
        Sinornithosaurus
        Sinornithosaurus is a genus of feathered dromaeosaurid dinosaur from the early Cretaceous Period of the Yixian Formation in what is now China. It was the fifth non–avian feathered dinosaur genus discovered by 1999...

    • Subfamily Unenlagiinae
      Unenlagiinae
      Unenlagiinae is a subfamily of Dromaeosauridae. Unenlagiines are one of the most basal lineages of dromaeosaurids. Unenlagiines are known from South America and Madagascar....

      • Austroraptor
        Austroraptor
        Austroraptor was a genus of dromaeosaurid dinosaur that lived about 70 million years ago during the Cretaceous period in what is now modern Argentina. The type species for the genus, Austroraptor cabazai, was described in late 2008 by Fernando Novas of the Museo Argentino de Ciencias Naturales...

      • Buitreraptor
        Buitreraptor
        Buitreraptor is a predatory dromaeosaurid theropod dinosaur from the Cretaceous of Argentina.Buitreraptor was described in 2005. The type species is Buitreraptor gonzalezorum...

      • Neuquenraptor
        Neuquenraptor
        Neuquenraptor is a dromaeosaurid theropod dinosaur of the Late Cretaceous of Argentina, one of the first dromaeosaurids found in the Southern Hemisphere....

      • Rahonavis
        Rahonavis
        Rahonavis is a genus of bird-like dinosaur from the Late Cretaceous of what is now northwestern Madagascar. It is known from a partial skeleton found in Maevarano Formation rocks at a quarry near Berivotra, Mahajanga Province...

      • Shanag
        Shanag
        Shanag is a genus of dromaeosaurid theropod dinosaur from the Early Cretaceous Period of Mongolia.The type species of Shanag is Shanag ashile. It was named and described by Alan Turner, Sunny Hai-Ching Hwang and Mark Norell in 2007. The generic name refers to the black-hatted dancers in the...

        ?
      • Unenlagia
        Unenlagia
        Unenlagia is a genus of, possibly dromaeosaurid, theropod dinosaur from the Late Cretaceous of Argentina....

      • Unquillosaurus
        Unquillosaurus
        Unquillosaurus is a genus of maniraptoran dinosaur from the late Cretaceous Period, discovered in Argentina. Known only from a single fossilized pubis , its total body length may have reached 2-3 meters .The type species Unquillosaurus ceibalii was described by Jaime Eduardo Powell in 1979...

    • Node Eudromaeosauria
      Eudromaeosauria
      Eudromaeosauria is a subgroup of terrestrial dromaeosaurid theropod dinosaurs. They were relatively large-bodied, feathered hypercarnivores that flourished in the Cretaceous Period.Eudromaeosaur fossils are known almost exclusively from the northern hemisphere...

      • Subfamily Dromaeosaurinae
        Dromaeosaurinae
        Dromaeosaurinae is a subfamily of Dromaeosauridae. Most dromaeosaurines lived in what is now the USA and Canada, , as well as Mongolia, , and possibly Denmark, , as well. Isolated teeth that may belong to African dromaeosaurines have also been discovered in Ethiopia...

      • Subfamily Saurornitholestinae
        Saurornitholestinae
        Saurornitholestinae is a subfamily of Dromaeosauridae.-Species:...

      • Subfamily Velociraptorinae
        Velociraptorinae
        Velociraptorinae is a subfamily of the theropod group Dromaeosauridae. Velociraptorine remains are found mostly in northern hemisphere. In Late Cretaceous, they are mostly present in Mongolia, Romania and China,and in early, in USA. The earliest velociraptorines are probably Nuthetes from the...


Phylogeny


Dromaeosauridae was first defined as a clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...

 by Paul Sereno
Paul Sereno
Paul Callistus Sereno is an American paleontologist from the University of Chicago who discovered several new dinosaur species on several continents. He has conducted excavations at sites as varied as Inner Mongolia, Argentina, Morocco, and Niger...

 in 1998, as the most inclusive natural group containing Dromaeosaurus but not Troodon
Troodon
Troodon is a genus of relatively small, bird-like dinosaur from the Late Cretaceous period . Discovered in 1855, it was among the first dinosaurs found in North America...

, Ornithomimus
Ornithomimus
Ornithomimus is a genus of ornithomimid dinosaur from the Late Cretaceous Period of what is now North America.In 1890 Ornithomimus velox was named by Othniel Charles Marsh on the basis of a foot and partial hand from the Maastrichtian Denver Formation. Another seventeen species have been named since...

or Passer
Passer
Passer is a genus of Old World sparrows. These sparrows are plump little brown or greyish birds often with black, yellow or white markings. Typically 10–20 cm long, they have short tails and stubby conical beaks...

. The various "subfamilies" have also been re-defined as clades, usually defined as all species closer to the groups namesake than to Dromaeosaurus or any namesakes of other sub-clades (for example, Makovicky defined the clade Unenlagiinae as all dromaeosaurids closer to Unenlagia than to Velociraptor). The Microraptoria is the only dromaeosaurid sub-clade not converted from a subfamily. Senter and colleagues expressly coined the name without the subfamily suffix -inae to avoid perceived issues with erecting a traditional family-group taxon, should the group be found to lie outside dromaeosauridae proper. Sereno offered a revised definition of the sub-group containing Microraptor to ensure that it would fall within Dromaeosauridae, and erected the subfamily Microraptorinae, attributing it to Senter et al., though this usage has only appeared on his online TaxonSearch database and has not been formally published.

The cladogram
Cladogram
A cladogram is a diagram used in cladistics which shows ancestral relations between organisms, to represent the evolutionary tree of life. Although traditionally such cladograms were generated largely on the basis of morphological characters, DNA and RNA sequencing data and computational...

 below follows a 2009 analysis by paleontologists Nicholas Longrich and Philip J. Currie.

Technical diagnosis



Dromaeosaurs are diagnosed by the following features; short T-shaped frontals
Frontal bone
The frontal bone is a bone in the human skull that resembles a cockleshell in form, and consists of two portions:* a vertical portion, the squama frontalis, corresponding with the region of the forehead....

 that form the rostral
Anatomical terms of location
Standard anatomical terms of location are designations employed in science that deal with the anatomy of animals to avoid ambiguities that might otherwise arise. They are not language-specific, and thus require no translation...

 boundary of the supratemporal fenestra; a caudolateral overhanging shelf of the squamosal
Squamosal
The squamosal is a bone of the head of higher vertebrates. It is the principal component of the cheek region in the skull, lying below the temporal series and otic notch and bounded anteriorly by postorbital. Posteriorly, the squamosal articulates with the posterior elements of the palatal complex,...

; a lateral process of the quadrate
Quadrate bone
The quadrate bone is part of a skull in most tetrapods, including amphibians, sauropsids , and early synapsids. In these animals it connects to the quadratojugal and squamosal in the skull, and forms part of the jaw joint .- Evolutionary variation :In snakes, the quadrate bone has become elongated...

 that contacts the quadratojugal
Quadratojugal
The quadratojugal is a small jaw bone that is present in most amphibians, reptiles, and birds, but has been lost in mammals. It is connected to the jugal as well as other bones, though these may vary with species....

; raised, stalked, parapophyses on the dorsal vertebrae, a modified pedal digit II; chevrons and prezygapophyses of the caudal vertebrae elongate and spanning several vertebrae; the presence of a subglenoid fossa on the coracoid.

In popular culture


A Deinonychus appears in John Brosnan
John Brosnan
John Raymond Brosnan was an Australian writer of both fiction and non-fiction works based around the fantasy and science fiction genres. He was born in Perth, Western Australia, and died in South Harrow, London, from acute pancreatitis...

's 1984 novel Carnosaur
Carnosaur (novel)
Carnosaur is a horror novel written by Australian author John Brosnan, under the pseudonym of Harry Adam Knight. A film adaptation was made in 1993 by Adam Simon....

and its film adaptation
Carnosaur (film)
Carnosaur is a 1993 horror film starring Diane Ladd as a mad scientist who plans to recreate dinosaurs and destroy humanity. The film is loosely based on a the novel Carnosaur by John Brosnan that was released in 1984, but the two have little in common...

 though the book itself received little press attention. Velociraptor
Velociraptor
Velociraptor is a genus of dromaeosaurid theropod dinosaur that existed approximately 75 to 71 million years ago during the later part of the Cretaceous Period. Two species are currently recognized, although others have been assigned in the past. The type species is V. mongoliensis; fossils...

, a dromaeosaurid, gained much attention after it was featured prominently in the 1993 Steven Spielberg film Jurassic Park
Jurassic Park (film)
Jurassic Park is a 1993 American science fiction adventure film directed by Steven Spielberg. The film is based on the novel of the same name by Michael Crichton. It stars Sam Neill, Laura Dern, Jeff Goldblum, Richard Attenborough, Martin Ferrero, and Bob Peck...

. However, the dimensions of the Velociraptor in the film are 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, adding that soon afterwards he named Utahraptor
Utahraptor
Utahraptor is a genus of theropod dinosaurs, including the largest known members of the family Dromaeosauridae. Fossil specimens date to the upper Barremian stage of the early Cretaceous period...

which was more the size depicted, or larger. Gregory S. Paul
Gregory S. Paul
Gregory Scott Paul is a freelance researcher, author and illustrator who works in paleontology, and more recently has examined sociology and theology. He is best known for his work and research on theropod dinosaurs and his detailed illustrations, both live and skeletal...

, in his book Predatory Dinosaurs of the World, considered Deinonychus antirrhopus a species of Velociraptor, and so rechristened the species Velociraptor antirrhopus. This taxonomic opinion has not been widely followed. Michael Crichton
Michael Crichton
John Michael Crichton , best known as Michael Crichton, was an American best-selling author, producer, director, and screenwriter, best known for his work in the science fiction, medical fiction, and thriller genres. His books have sold over 200 million copies worldwide, and many have been adapted...

 adopted this synonymization
Synonym (taxonomy)
In scientific nomenclature, a synonym is a scientific name that is or was used for a taxon of organisms that also goes by a different scientific name. For example, Linnaeus was the first to give a scientific name to the Norway spruce, which he called Pinus abies...

 of the two genera in his novels, on which the first two films were based. The depiction of the dromaeosaurid in the original Jurassic Park film, while accurate for its time, is now known to have been inaccurate in many respects, including the lack of feathers
Feathered dinosaurs
The realization that dinosaurs are closely related to birds raised the obvious possibility of feathered dinosaurs. Fossils of Archaeopteryx include well-preserved feathers, but it was not until the early 1990s that clearly non-avialan dinosaur fossils were discovered with preserved feathers...

. While Jurassic Park III
Jurassic Park III
Jurassic Park III is a 2001 American science fiction film and the third of the Jurassic Park franchise. It is the only film in the series that is neither directed by Steven Spielberg nor based on a book by Michael Crichton, though numerous scenes in the movie were taken from Crichton's two books,...

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
The Land Before Time (series)
The Land Before Time is a series of animated films centered on dinosaurs. The series began in 1988 with The Land Before Time, directed and produced by Don Bluth and executive produced by George Lucas and Steven Spielberg. It was followed by a total of 12 direct-to-video sequels, though none...

films, beginning with the third.

External links



  • 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