# Microraptor

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Extinct genus of dinosaurs

Microraptor Temporal range: Early Cretaceous, 120 Ma PreꞒ Ꞓ O S D C P T J K Pg N B V H B Apt. Albian C T C S Cam. M Holotype specimen IVPP V 13352, with white arrows pointing at preserved feathers Scientific classification Kingdom: Animalia Phylum: Chordata Class: Reptilia Clade: Dinosauria Clade: Saurischia Clade: Theropoda Family: †Dromaeosauridae Clade: †Microraptoria Genus: †Microraptor Xu et al., 2000 Type species †Microraptor zhaoianus Xu et al., 2000 Other species †M. gui Xu et al., 2003 †M. hanqingi Gong et al., 2012 Synonyms Cryptovolans pauli Czerkas et al., 2002 "Tetrapterornis" Miller, 2004 (nomen nudum)[1]

***Microraptor*** ([Greek](/source/Greek_language), μικρός, *mīkros*: "small"; [Latin](/source/Latin_language), *raptor*: "one who seizes") is a [genus](/source/Genus) of small, four-winged [dromaeosaurid](/source/Dromaeosaurid) [dinosaurs](/source/Dinosaur). Numerous well-preserved [fossil](/source/Fossil) specimens have been recovered from [Liaoning](/source/Liaoning), [China](/source/China). They date from the early [Cretaceous](/source/Cretaceous) [Jiufotang Formation](/source/Jiufotang_Formation) ([Aptian](/source/Aptian) stage), 125 to 120 million [years](/source/Year) ago. Three species have been named (*M. zhaoianus*, *M. gui*, and *M. hanqingi*), though further study has suggested that all of them represent variation in a single species, which is properly called *M. zhaoianus*. ***Cryptovolans***, initially described as another four-winged dinosaur, is usually considered to be a synonym of *Microraptor*.[2]

Like *[Archaeopteryx](/source/Archaeopteryx)*, well-preserved fossils of *Microraptor* provide important evidence about the evolutionary relationship between [birds](/source/Bird) and earlier dinosaurs. *Microraptor* had long [pennaceous feathers](/source/Pennaceous_feather) that formed aerodynamic surfaces on the arms and tail but also on the legs. This led paleontologist [Xu Xing](/source/Xu_Xing_(paleontologist)) in 2003 to describe the first specimen to preserve this feature as a "four-winged dinosaur" and to speculate that it may have [glided](/source/Gliding_flight) using all four limbs for lift. Subsequent studies have suggested that *Microraptor* was capable of powered flight as well.

*Microraptor* was among the most abundant non-[avialan](/source/Avialae) dinosaurs in its ecosystem, and the genus is represented by more fossils than any other dromaeosaurid, with possibly over 300 fossil specimens represented across various museum collections.[3] One specimen in particular shows evidence of active [primary](/source/Primary_feather) sequential [moulting](/source/Moulting) similar to that of modern volant (flight-capable) birds, which is one of the few known fossil evidence of such behavior among pennaraptoran dinosaurs.[4]

## History

### Naming controversy

Main article: [Archaeoraptor](/source/Archaeoraptor)

The "[Archaeoraptor](/source/Archaeoraptor)" fossil; the tail belongs to *Microraptor*

The initial naming of *Microraptor* was controversial, because of the unusual circumstances of its first description. The first specimen to be described was part of a chimeric specimen—a patchwork of different feathered dinosaur species (*Microraptor* itself, *[Yanornis](/source/Yanornis)* and an as-of-yet undescribed third species) assembled from multiple specimens in China and smuggled to the USA for [sale](/source/Fossil_collecting). After the forgery was revealed by [Xu Xing](/source/Xu_Xing_(paleontologist)) of [Beijing](/source/Beijing)'s [Institute of Vertebrate Paleontology and Paleoanthropology](/source/Institute_of_Vertebrate_Paleontology_and_Paleoanthropology), [Storrs L. Olson](/source/Storrs_L._Olson), curator of birds in the [National Museum of Natural History](/source/National_Museum_of_Natural_History) of the [Smithsonian Institution](/source/Smithsonian_Institution), published a description of the Microraptor's tail in an obscure journal, giving it the name *Archaeoraptor liaoningensis* in an attempt to remove the name from the paleornithological record by assigning it to the part least likely to be a bird.[5] However, Xu had discovered the remains of the specimen from which the tail had been taken and published a description of it later that year, giving it the name *Microraptor zhaoianus*.[6]

Since the two names designate the same individual as the [type](/source/Type_(biology)) specimen, *Microraptor zhaoianus* would have been a [junior objective synonym](/source/Junior_objective_synonym) of *Archaeoraptor liaoningensis* and the latter, if valid, would have had priority under the [International Code of Zoological Nomenclature](/source/International_Code_of_Zoological_Nomenclature). However, there is some doubt whether Olson in fact succeeded in meeting all the formal requirements for establishing a new taxon. Notably, Olson designated the specimen as a [lectotype](/source/Lectotype), before an actual type species was formally erected.[7] A similar situation arose with *[Tyrannosaurus rex](/source/Tyrannosaurus_rex)* and *Manospondylus gigas*, in which the former became a *nomen protectum* (protected name) and the latter a *[nomen oblitum](/source/Nomen_oblitum)* (disused name) due to revisions in the ICZN rules that took place on 31 December 1999.[8] In addition, Xu's name for the type specimen (*Microraptor*) was subsequently used more frequently than the original name; as such, this and the chimeric nature of the specimen would render the name "Archaeoraptor" a *nomen vanum* (as it was improperly described) and the junior synonym *Microraptor* a *nomen protectum* (as it has been used in more published works than "Archaeoraptor" and was properly described).[9]

### Additional specimens

Skeletal restorations of various specimens

The first specimen referred to *Microraptor* represented a small individual and included faint feather remnants, but was otherwise not well preserved and lacked a skull. In 2002 [Mark Norell](/source/Mark_Norell) et al. described another specimen, BPM 1 3-13, which they did not name or refer to an existing species.[10] Later that year [Stephen Czerkas](/source/Stephen_A._Czerkas) et al. named the specimen *Cryptovolans pauli*, and referred two additional specimens (the first to show well-preserved feathers) to this species. The generic name was derived from Greek *kryptos*, "hidden", and [Latin](/source/Latin) *volans*, "flying". The [specific name](/source/Specific_name_(zoology)), *pauli*, honors [paleontologist](/source/Paleontology) [Gregory S. Paul](/source/Gregory_S._Paul), who had long proposed that dromaeosaurids evolved from flying ancestors.[11]

The [type specimens](/source/Type_specimen) of *C. pauli* were collected from the [Jiufotang Formation](/source/Jiufotang_Formation), dating from the early [Albian](/source/Albian) and now belong to the collection of the Paleontology Museum of Beipiao, in [Liaoning](/source/Liaoning), China. They are referred to by the inventory numbers LPM 0200, the [holotype](/source/Holotype); LPM 0201, its counterslab (slab and counterslab together represent the earlier BPM 1 3-13); and the [paratype](/source/Paratype) LPM 0159, a smaller skeleton. Both individuals are preserved as articulated compression fossils; they are reasonably complete but partially damaged.[11]

Specimen at the [Beijing Museum of Natural History](/source/Beijing_Museum_of_Natural_History)

Czerkas et al. (2002) diagnosed the genus on the basis of having primary feathers (which in the authors' opinion made it a [bird](/source/Bird)), a co-ossified sternum, a tail consisting of 28 to 30 vertebrae and a third finger with a short phalanx III-3.[11] Some of the feathers Czerkas described as primary were actually attached to the leg, rather than the arm. This, along with most of the other diagnostic characters, is also present in the genus *Microraptor*, which was first described earlier than *Cryptovolans*.[12] However, BPM 1 3-13 has a longer tail, proportionately, than other *Microraptor* specimens that had been described by 2002, which have 24 to 26 tail vertebrae.[10]

Subsequent studies (and more specimens of *Microraptor*) have shown that the features used to distinguish *Cryptovolans* are not unique, but are present to varying degrees across various specimens. In a review by Phil Senter and colleagues in 2004, the scientists suggested that all these features represented individual variation across various age groups of a single *Microraptor* species, making the name *Cryptovolans pauli* and *Microraptor gui* junior synonyms of *Microraptor zhaoianus*.[2] Many other researchers, including Alan Feduccia and Tom Holtz, have since supported its synonymy.[13][14] *M. gui* has been accepted as a distinct species with the specimen reported in 2013 being distinguishable from the type specimen of *M. zhaoianus*.[15]

A new specimen of *Microraptor*, BMNHC PH881, showed several features previously unknown in the animal, including the probably glossy-black iridescent plumage coloration. The new specimen also featured a bifurcated tailfan, similar in shape to previously known *Microraptor* tailfans except sporting a pair of long, narrow feathers at the center of the fan. The new specimen also showed no sign of the nuchal crest, indicating that the crest inferred from the holotype specimen may be an artifact of [taphonomic](/source/Taphonomy) distortion.[16][17]

Numerous further specimens likely belonging to *Microraptor* have been uncovered, all from the Shangheshou Bed of the [Jiufotang Formation](/source/Jiufotang_Formation) in Liaoning, China. In fact, *Microraptor* is the most abundant non-avialan dinosaur fossil type found in this formation.[18] In 2010, it was reported that there were over 300 undescribed specimens attributable to *Microraptor* or its close relatives among the collections of several Chinese museums, though many had been altered or composited by private fossil collectors.[3]

### Study and debate

Fossil specimen

Norell et al. (2002) described BPM 1 3-13 as the first dinosaur known to have flight feathers on its legs as well as on its arms.[19]

Czerkas (2002) mistakenly described the fossil as having no long feathers on its legs, but only on its hands and arms, as he illustrated on the cover of his book *Feathered Dinosaurs and the Origin of Flight*.[11] In his discussion of *Cryptovolans* in this book, Czerkas strongly denounces Norell's conclusions; "The misinterpretation of the primary wing feathers as being from the hind legs stems directly to [*sic*] seeing what one believes and wants to see".[11] Czerkas also denounced Norell for failing to conclude that [dromaeosaurs](/source/Dromaeosauridae) are birds, accusing him of succumbing to "...the blinding influences of preconceived ideas".[11] The [crown group](/source/Crown_group) definition of Aves, as a subset of [Avialae](/source/Avialae), the explicit definition of the term "bird" that Norell employs, would definitely exclude BPM 1 3-13. However, he does not consider the specimen to belong to Avialae either.[19]

Czerkas's interpretation of the hindleg feathers noted by Norell proved to be incorrect the following year when additional specimens of *Microraptor* were published by Xu and colleagues, showing a distinctive "hindwing" completely separate from the forelimb wing. The first of these specimens was discovered in 2001, and between 2001 and 2003 four more specimens were bought from private collectors by Xu's museum, the [Institute of Vertebrate Paleontology and Paleoanthropology](/source/Institute_of_Vertebrate_Paleontology_and_Paleoanthropology). Xu also considered these specimens, most of which had hindwings and proportional differences from the original *Microraptor* specimen, to be a new species, which he named *Microraptor gui*. However, Senter also questioned this classification, noting that as with *Cryptovolans*, most of the differences appeared to correspond with size, and likely age differences.[2] Two further specimens, classified as *M. zhaoianus* in 2002 (*M. gui* had not yet been named), have also been described by Hwang and colleagues.[20]

Czerkas also believed that the animal may have been able to fly better than *[Archaeopteryx](/source/Archaeopteryx)*, the animal usually referred to as the earliest known bird. He cited the fused sternum and asymmetrical feathers, and argued that *Microraptor* has modern bird features that make it more derived than *Archaeopteryx*. Czerkas cited the fact that this possibly volant animal is also very clearly a dromaeosaurid to suggest that the [Dromaeosauridae](/source/Dromaeosauridae) might actually be a basal bird group, and that later, larger, species such as *[Deinonychus](/source/Deinonychus)* were secondarily flightless (Czerkas, 2002). The current consensus is that there is not enough evidence to conclude whether dromaeosaurs descended from an ancestor with some aerodynamic abilities. The work of Xu et al. (2003) suggested that basal dromaeosaurs were probably small, arboreal, and could glide.[21] The work of Turner et al. (2007) suggested that the ancestral dromaeosaur could not glide or fly, but that there was good evidence that it was small-bodied (around 65 cm long and 600–700 g in mass).[22]

## Description

Wingspan and body size compared with a human

*Microraptor* was among the [smallest-known non-avian dinosaurs](/source/Dinosaur_size), with the holotype of *M. gui* measuring 77 centimetres (2.53 ft) in length, 88–94 centimetres (2.89–3.08 ft) in wingspan and weighing 0.5–1.4 kilograms (1.1–3.1 lb).[23][24][25] There are larger specimens which would have measured at least 80 centimetres (2.6 ft) in length, more than 99 centimetres (3.25 ft) in wingspan and weighed 1.25–1.88 kilograms (2.8–4.1 lb).[25][a] Aside from their extremely small size, *Microraptor* were among the first non-[avialan](/source/Avialae) dinosaurs discovered with the impressions of feathers and wings. Seven specimens of *M. zhaoianus* have been described in detail, from which most feather impressions are known. Unusual even among early birds and feathered dinosaurs, *Microraptor* is one of the few known bird precursors to sport long flight feathers on the legs as well as the wings. Their bodies had a thick covering of feathers, with a diamond-shaped fan on the end of the tail (possibly for added stability during flight). Xu et al. (2003) compared the longer plumes on *Microraptor*'s head to those of the [Philippine eagle](/source/Philippine_eagle). Bands of dark and light present on some specimens may indicate color patterns present in life,[20] though at least some individuals almost certainly possessed an iridescent black coloration.[16]

### Distinguishing anatomical features

A diagnosis is a statement of the anatomical features of an organism (or group) that collectively distinguish it from all other organisms. Some, but not all, of the features in a diagnosis are also autapomorphies. An autapomorphy is a distinctive anatomical feature that is unique to a given organism. Several anatomical features found in *Microraptor*, such as a combination of unserrated and partially serrated teeth with constricted 'waists', and unusually long upper arm bones, are shared with both primitive avians and primitive [troodontids](/source/Troodontidae). *Microraptor* is particularly similar to the basal troodontid *[Sinovenator](/source/Sinovenator)*; in their 2002 description of two *M. zhaoianus* specimens, Hwang et al. note that this is not particularly surprising, given that both *Microraptor* and *Sinovenator* are very primitive members of two closely related groups, and both are close to the [deinonychosaurian](/source/Dromaeosauridae) split between dromaeosaurids and troodontids.[20]

### Coloration

[Restoration](/source/Paleoart) of *M. gui* with coloration based on fossilized melanosomes

In March 2012, Quanguo Li et al. determined the plumage coloration of *Microraptor* based on the new specimen BMNHC PH881, which also showed several other features previously unknown in *Microraptor*. By analyzing the fossilized melanosomes (pigment cells) in the fossil with [scanning electron microscope](/source/Scanning_electron_microscope) techniques, the researchers compared their arrangements to those of modern birds. In *Microraptor*, these cells were shaped in a manner consistent with black, glossy coloration in modern birds. These rod-shaped, narrow melanosomes were arranged in stacked layers, much like those of a modern [starling](/source/Common_starling), and indicated [iridescence](/source/Iridescence) in the plumage of *Microraptor*. Though the researchers state that the true function of the iridescence is yet unknown, it has been suggested that the tiny dromaeosaur was using its glossy coat as a form of communication or sexual display, much as in modern iridescent birds.[16][17]

## Classification

Size of *Microraptor* (1) compared with other [dromaeosaurs](/source/Dromaeosauridae)

Specimen in the Shandong Tianyu Museum of Nature

The cladogram below follows a 2012 analysis by paleontologists Phil Senter, James I. Kirkland, Donald D. DeBlieux, Scott Madsen and Natalie Toth.[27]

Dromaeosauridae Xiaotingia Unenlagiinae Shanag Eudromaeosauria Saurornitholestinae Velociraptorinae Dromaeosaurinae Microraptoria Tianyuraptor Hesperonychus Microraptor sp. Microraptor gui Microraptor zhaoianus Cryptovolans Graciliraptor Sinornithosaurus

In a 2024 paper which reported the smallest known juvenile specimen of *Microraptor*, Wang and Pei included [microraptorians](/source/Microraptoria) and [eudromaeosaurians](/source/Eudromaeosauria) within a new clade Serraraptoria.[28]

## Paleobiology

### Wings and flight

*M. gui* [holotype](/source/Holotype) (IVPP V 13352) under two different UV light filters, revealing the extent of preserved feathers and soft tissue

*Microraptor* had four [wings](/source/Wing), one on each of its forelimbs and hindlimbs, somewhat resembling one possible arrangement of the quartet of flight surfaces on a [tandem wing](/source/Tandem_wing) aircraft of today. It had long [pennaceous feathers](/source/Pennaceous_feather) on arms and hands 10–20 cm long (3.9–7.9 in) with legs and feet 11–15 cm long (4.3–5.9 in). The long feathers on the legs of *Microraptor* were true flight feathers as seen in modern [birds](/source/Bird), with asymmetrical vanes on the arm, leg, and tail feathers. As in modern bird wings, *Microraptor* had both primary (anchored to the hand) and secondary (anchored to the arm) flight feathers. This standard wing pattern was mirrored on the hindlegs, with [flight feathers](/source/Flight_feather) anchored to the upper foot bones as well as the upper and lower leg. Though not apparent in most fossils under natural light, due to obstruction from decayed soft tissue, the feather bases extended close to or in contact with the bones, as in modern birds, providing strong anchor points.[29]

It was originally thought that *Microraptor* was a [glider](/source/Gliding_flight), and probably lived mainly in trees, because the hindwings anchored to the feet of *Microraptor* would have hindered their ability to run on the ground.[30] Some paleontologists have suggested that feathered dinosaurs used their wings to parachute from trees, possibly to attack or ambush prey on the ground, as a precursor to gliding or true flight.[31] In their 2007 study, Chatterjee and Templin tested this hypothesis as well, and found that the combined wing surface of *Microraptor* was too narrow to successfully parachute to the ground without injury from any significant height. However, the authors did leave open the possibility that *Microraptor* could have parachuted short distances, as between closely spaced tree branches.[23][31] Wind tunnel experiments have demonstrated that sustaining a high-lift coefficient at the expense of high drag was likely the most efficient strategy for *Microraptor* when gliding between low elevations. *Microraptor* did not require a sophisticated, 'modern' wing morphology to be an effective glider.[32] However, the idea that *Microraptor* was an arboreal glider relies on it to have regularly climbed or even lived in trees, when study of its anatomy have shown that its limb proportions fall in line with modern ground birds rather than climbers, and its skeleton shows none of the expected adaptations in animals specialized for climbing trees.[33][26]

Describing specimens originally referenced as a distinctive species (*Cryptovolans pauli*), paleontologist Stephen Czerkas argued *Microraptor* may have been a powered flier, and indeed possibly a better flyer than *[Archaeopteryx](/source/Archaeopteryx)*. He noted that the fused sternum of *Microraptor*, asymmetrical feathers, and features of the shoulder girdle indicated that it could fly under its own power, rather than merely gliding. Today, most scientists agree that *Microraptor* had the anatomical features expected of a flying animal, though it would have been a less advanced form of flight compared to birds. For example, some studies suggest the shoulder joint was too primitive to allow a full flapping flight stroke. In the ancestral anatomy of theropod dinosaurs, the shoulder socket faced downward and slightly backward, making it impossible for the animals to raise their arms vertically, a prerequisite for the flapping flight stroke in birds. Studies of maniraptoran anatomy have suggested that the shoulder socket did not shift into the bird-like position of a high, upward orientation close to the [vertebral](/source/Vertebra) column until relatively advanced avialans like the [enantiornithes](/source/Enantiornithes) appeared.[34] However, other scientists have argued that the shoulder girdle in some [paravian](/source/Paraves) theropods, including *Microraptor*, is curved in such a way that the shoulder joint could only have been positioned high on the back, allowing for a nearly vertical upstroke of the wing. This possibly advanced shoulder anatomy, combined with the presence of a [propatagium](/source/Patagium) linking the wrist to the shoulder (which fills the space in front of the flexed wing and may support the wing against drag in modern birds) and an [alula](/source/Alula), much like a "thumb-like" form of [leading edge slot](/source/Leading_edge_slot), may indicate that *Microraptor* was capable of true, powered flight.[35]

Other studies have demonstrated that the wings of *Microraptor* were large enough to generate the lift necessary for powered launching into flight even without a fully vertical flight stroke. A 2016 study of incipient flight ability in paravians demonstrated that *Microraptor* was capable of [wing-assisted incline running](/source/Wing-assisted_incline_running), as well as wing-assisted leaping and even ground-based launching.[26]

Stephen Czerkas, Gregory S. Paul, and others have argued that the fact *Microraptor* could fly and yet is also very clearly a dromaeosaurid suggests that the [Dromaeosauridae](/source/Dromaeosauridae), including later and larger species such as *[Deinonychus](/source/Deinonychus)*, were secondarily flightless. The work of Xu and colleagues also suggested that the ancestors of dromaeosaurids were probably small, arboreal, and capable of [gliding](/source/Gliding_flight), although later discoveries of more primitive dromaeosaurids with short forelimbs unsuitable for gliding have cast doubt on this view.[30][22] Work done on the question of flight ability in other paravians, however, showed that most of them probably would not have been able to achieve enough lift for powered flight, given their limited flight strokes and relatively smaller wings. These studies concluded that *Microraptor* probably evolved flight and its associated features (fused sternum, alula, etc.) independently of the ancestors of birds.[26][36][37][25] In 2024, Kiat and O'Connor analyzed that Mesozoic birds and *Microraptor* had remex morphologies that are consistent with modern volant birds, while [anchiornithids](/source/Anchiornithidae) and *[Caudipteryx](/source/Caudipteryx)* were secondarily flightless.[38]

### Hindwing posture

Wind tunnel experiments with different wing configurations

[Sankar Chatterjee](/source/Sankar_Chatterjee) suggested in 2005 that, in order for *Microraptor* to [glide](/source/Gliding_flight) or fly, the forewings and hindwings must have been on different levels (as on a [biplane](/source/Biplane)) and not overlaid (as on a [dragonfly](/source/Dragonfly)), and that the latter posture would have been anatomically impossible. Using this biplane model, Chatterjee was able to calculate possible methods of gliding and determined that *Microraptor* most likely employed a *[phugoid](/source/Phugoid)* style of gliding: launching itself from a perch, the animal would have swooped downward in a deep U-shaped curve and then lifted again to land on another tree. The feathers not directly employed in the biplane [wing](/source/Wing) structure, like those on the [tibia](/source/Tibia) and the [tail](/source/Tail), could have been used to control drag and alter the [flight path](/source/Airway_(aviation)), [trajectory](/source/Trajectory), etc. The orientation of the hindwings would also have helped the animal control its gliding flight. Chatterjee also used computer [algorithms](/source/Algorithm) that test [animal flight](/source/Flying_and_gliding_animals) capacity to test whether or not *Microraptor* was capable of true, powered flight, as opposed to or in addition to passive gliding. The resulting data showed that *Microraptor* did have the requirements to sustain level powered flight, so it is theoretically possible that the animal flew, as opposed to gliding.[23]

Some paleontologists have doubted the biplane hypothesis, and have proposed other configurations. A 2010 study by Alexander et al. described the construction of a lightweight three-dimensional physical model used to perform glide tests. Using several hindleg configurations for the model, they found that the biplane model, while not unreasonable, was structurally deficient and needed a heavy-headed weight distribution for stable gliding, which they deemed unlikely. The study indicated that a laterally abducted hindwing structure represented the most biologically and aerodynamically consistent configuration for *Microraptor*.[3] A further analysis by Brougham and Brusatte, however, concluded that Alexander's model reconstruction was not consistent with all of the available data on *Microraptor* and argued that the study was insufficient for determining a likely flight pattern for *Microraptor*. Brougham and Brusatte criticized the anatomy of the model used by Alexander and his team, noting that the hip anatomy was not consistent with other dromaeosaurs. In most dromaeosaurids, features of the hip bone prevent the legs from splaying horizontally; instead, they are locked in a vertical position below the body. Alexander's team used a specimen of *Microraptor* which was crushed flat to make their model, which Brougham and Brusatte argued did not reflect its actual anatomy.[39] Later in 2010, Alexander's team responded to these criticisms, noting that the related dromaeosaur *[Hesperonychus](/source/Hesperonychus)*, which is known from complete hip bones preserved in three dimensions, also shows hip sockets directed partially upward, possibly allowing the legs to splay more than in other dromaeosaurs.[40] However, Hartman and colleagues suggested that *Hesperonychus* is not a dromaeosaur, but actually an [avialan](/source/Avialae) close to modern [birds](/source/Bird) like *[Balaur bondoc](/source/Balaur_bondoc)* based on phylogenetic analyses in 2019.[41]

### Ground movement

Restoration of two individuals by the ground

Due to the extent of the hindwings onto most of the animal's foot, many scientists have suggested that *Microraptor* would have been awkward during normal ground movement or running. The front wing feathers would also have hindered *Microraptor* when on the ground, due to the limited range of motion in the wrist and the extreme length of the wing feathers. A 2010 study by Corwin Sullivan and colleagues showed that, even with the wing folded as far as possible, the feathers would still have dragged along the ground if the arms were held in a neutral position, or extended forward as in a predatory strike. Only by keeping the wings elevated, or the upper arm extended fully backward, could *Microraptor* have avoided damaging the wing feathers. Therefore, it may have been anatomically impossible for *Microraptor* to have used its clawed forelimbs in capturing prey or manipulating objects.[42]

### Implications

[William Beebe](/source/William_Beebe)'s hypothetical "*Tetrapteryx*" with four wings, 1915

The unique wing arrangement found in *Microraptor* raised the question of whether the evolution of flight in modern birds went through a four-winged stage, or whether four-winged gliders like *Microraptor* were an evolutionary side-branch that left no descendants. As early as 1915, [naturalist](/source/Natural_history) [William Beebe](/source/William_Beebe) had argued that the evolution of bird flight may have gone through a [four-winged (or *tetrapteryx*) stage](/source/Proavis).[43] Chatterjee and Templin did not take a strong stance on this possibility, noting that both a conventional interpretation and a tetrapteryx stage are equally possible. However, based on the presence of unusually long leg feathers in various feathered dinosaurs, *[Archaeopteryx](/source/Archaeopteryx)*, and some modern birds such as raptors, as well as the discovery of further dinosaurs with long primary feathers on their feet (such as *[Pedopenna](/source/Pedopenna)*), the authors argued that the current body of evidence, both from morphology and phylogeny, suggests that bird flight did shift at some point from shared limb dominance to front-limb dominance and that all modern birds may have evolved from four-winged ancestors, or at least ancestors with unusually long leg feathers relative to the modern configuration.[23]

### Feeding

Cast in [Horniman Museum](/source/Horniman_Museum)

In 2010 researchers announced that further preparation of the type fossil of *M. zhaoianus* revealed preserved probable gut contents, and a full study on them was later published in 2022 by David Hone and colleagues. These consisted of the remains of a mammal, primarily a complete and articulated right foot (including all [tarsals](/source/Tarsal_bone), [metatarsals](/source/Metatarsals), and most of the [phalanges](/source/Phalanges)) as well as the shafts of additional long bones and potentially other fragments. The foot skeleton is similar to those of *[Eomaia](/source/Eomaia)* and *[Sinodelphys](/source/Sinodelphys)*. It corresponds to an animal with an estimated snout to vent length of 80 mm (3.1 in) and a mass of 13–43 g (0.46–1.52 oz). The unguals of the foot are less curved than in *Eomaia* or *Sinodelphys*, indicating that the mammal could climb but less effectively than in the two latter genera and so was likely not arboreal but potentially scansorial.[44][45]

It is ambiguous whether the mammal had been predated upon or scavenged by *Microraptor*, although the lack of other definitive body parts consumed may suggest the low-muscle mass foot may have been eaten during a late stage of carcass consumption, possibly through scavenging. The find is a rare example of a theropod definitively consuming a Mesozoic mammal.[44][45] The only other two examples are the indeterminate [tyrannosauroid](/source/Tyrannosauroid) specimen GMV 2124 (also known as NGMC 2124) and the holotype of *[Huadanosaurus](/source/Huadanosaurus)*, both of which are previously attributed to *[Sinosauropteryx](/source/Sinosauropteryx)*.[46]

In the 6 December 2011 issue of *Proceedings of the National Academy of Sciences*, Jingmai O'Connor and coauthors described a specimen of *Microraptor gui* containing bones of an arboreal [enantiornithean](/source/Enantiornithean) bird in its abdomen, specifically a partial wing and feet. Their position implies the bird was swallowed whole and head-first, which the authors interpreted as implying that the *Microraptor* had caught and consumed the bird in the trees, rather than scavenging it.[47]

In 2013 researchers announced that they had found fish scales in the abdominal cavity of another *M. gui* specimen.[15] The authors contradicted the prior suggestion that *M. gui* hunted only in an arboreal environment, proposing that it was also an adept hunter of fish as well. They further argued that the specimen showed a probable adaptation to a fish-eating diet, pointing to the first three teeth of the mandible being inclined anterodorsally, a characteristic often associated with piscivory.[15] They concluded that *Microraptor* was an opportunistic feeder, hunting the most common prey in both arboreal and aquatic habitats.[15]

Both of these studies regarded each gut contents as instances of predation. However, Hone and colleagues (2022) questioned the reliability of these interpretations and wrote that both could just as equally be attributed to scavenging. Further, they argued against *Microraptor* being a specialist in either or both arboreal or aquatic hunting, citing the broad range of vertebrate gut contents (i.e. fish, mammals, lizards, birds) as evidence for a generalist hunting strategy, and that neither required that *Microraptor* being a specialist for hunting in either habitats.[45]

In 2019, a new genus of [scleroglossan](/source/Scleroglossa) [lizard](/source/Lizard) (*[Indrasaurus](/source/Indrasaurus)*) was described from a specimen found in the stomach of a *Microraptor*. The *Microraptor* apparently swallowed its prey head first, a behavior typical of modern [carnivorous](/source/Carnivore) [birds](/source/Bird) and lizards. The *Indrasaurus* bones lacked marked pitting and scarring, indicating that the *Microraptor* died shortly after eating the lizard and before significant digestion had occurred.[48]

Unlike its fellow [paravian](/source/Paraves) *[Anchiornis](/source/Anchiornis)*, *Microraptor* has never been found with [gastric pellets](/source/Pellet_(ornithology)), despite the existence of four *Microraptor* specimens that preserve stomach contents. This suggests that *Microraptor* passed indigestible fur, feathers, and bits of bone in its droppings instead of producing pellets.[48]

Based on the morphology of the [scleral ring](/source/Scleral_ring) of the eye, it has been suggested *Microraptor* hunted at night.[49] However, the discovery of dark and glossy plumage in *Microraptor* may suggest otherwise, as no modern birds with comparable plumage are known to be nocturnal.[16]

## See also

- [Dinosaurs portal](https://en.wikipedia.org/wiki/Portal:Dinosaurs)

- [Dinosaur coloration](/source/Dinosaur_coloration)

- [Timeline of dromaeosaurid research](/source/Timeline_of_dromaeosaurid_research)

## Notes

1. **[^](#cite_ref-27)** The wingspan estimate is based on the equation presented in the study by Dececchi et al. (2016) which states that the wingspan of the paravians in the study would have been 2.1 times the wing length.[26] In case of *Microraptor*, the holotype had a wing length of 42 centimetres (1.38 ft), resulting in a wingspan of more than 88 centimetres (2.89 ft). The larger specimen QV1002 measured 3 centimetres (1.2 in) longer than the holotype in precaudal length, and had wing length of 47.2 centimetres (1.55 ft), resulting in a wingspan of more than 99 centimetres (3.25 ft).[25]

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## External links

[Wikispecies](/source/Wikispecies) has information related to ***[Microraptor](https://species.wikimedia.org/wiki/Microraptor)***.

- [Dromaeosauridae, *Relationship with birds*](/source/Dromaeosauridae#Relationship_with_birds)

- [A model of *Microraptor*/Cryptovolans pauli by Boban Filipovic](https://web.archive.org/web/20040306034207/http://www.indyrad.iupui.edu/public/jrafert/Filipovic/newfeather/Microraptor-gui-%28Cryptovol.jpg)

- Jacqui Hayes: [Bird wings evolved from biplane dinosaurs](http://www.cosmosmagazine.com/node/984) [Archived](https://web.archive.org/web/20070127002632/http://www.cosmosmagazine.com/node/984) 2007-01-27 at the [Wayback Machine](/source/Wayback_Machine) COSMOS magazine

- [The Four-Winged Dinosaur](https://www.pbs.org/wgbh/nova/microraptor/) - PBS website for the *Nova* documentary

- NewScientist [Microraptor's glossy black feather coat reconstructed](https://www.newscientist.com/articleimages/dn21552/1-microraptors-glossy-black-feather-coat-reconstructed.html)

- [nationalgeographic.com 2012-03-08 Ed Yong, A shiny dinosaur four-winged Microraptor gets color and gloss](https://web.archive.org/web/20130618224030/http://phenomena.nationalgeographic.com/2012/03/08/a-shiny-dinosaur-four-winged-microraptor-gets-colour-and-gloss/)

- [nationalgeographic.com 2008-10-08 Ed Yong, Microraptor–the dinosaur that flew like a biplane](https://web.archive.org/web/20130123100759/http://phenomena.nationalgeographic.com/2008/10/08/microraptor-the-dinosaur-that-flew-like-a-biplane/)

v t e Dromaeosauridae Kingdom: Animalia Phylum: Chordata Class: Sauropsida Clade: Dinosauria Clade: Theropoda Clade: Paraves Avemetatarsalia see Avemetatarsalia Theropoda see Theropoda Maniraptora see Maniraptora Dromaeosauridae see below↓ Dromaeosauridae Dromaeosauridae Daurlong Hesperonychus Pyroraptor? Shanag Tianyuraptor Variraptor? Zhenyuanlong Halszkaraptorinae/-idae? Halszkaraptor Hulsanpes Mahakala Natovenator Unenlagiinae/-idae? Austroraptor Buitreraptor Dakotaraptor? Diuqin Imperobator? Kank Neuquenraptor Ornithodesmus? Overoraptor? Pamparaptor Pyroraptor? Rahonavis? Unenlagia Unquillosaurus? Variraptor? Ypupiara Microraptoria Changyuraptor Graciliraptor Jian Microraptor Sinornithosaurus Wulong Zhongjianosaurus Eudromaeosauria Balaur? Bambiraptor Dineobellator Vectiraptor Saurornitholestinae Atrociraptor Bambiraptor? Saurornitholestes Dromaeosaurinae Achillobator Dakotaraptor? Deinonychus? Dromaeosauroides Dromaeosaurus Itemirus Saurornitholestes? Utahraptor Yurgovuchia Zapsalis Velociraptorinae Acheroraptor Adasaurus Boreonykus? Deinonychus? Kansaignathus Kuru Linheraptor Luanchuanraptor? Nuthetes? Saurornitholestes? Shri Tsaagan Velociraptor See also: Timeline Category

Taxon identifiers Microraptor Wikidata: Q310537 Wikispecies: Microraptor EoL: 4433549 GBIF: 4822946 Open Tree of Life: 4946091 Paleobiology Database: 68238 Taxonomicon: 146681 ZooBank: 3DD13702-B988-4137-935A-516440F9701D

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Adapted from the Wikipedia article [Microraptor](https://en.wikipedia.org/wiki/Microraptor) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Microraptor?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.