Microraptor
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224929205
2008-07-11T01:28:12Z
Captmondo
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Wikilinking "holotype", plus added place/link where the cast can be seen
{{Taxobox
| name = ''Microraptor''
| fossil_range = [[Early Cretaceous]]
| image = MicroraptorGui-PaleozoologicalMuseumOfChina-May23-08.jpg
| image_width = 250px
| image_caption = Cast of the [[holotype]] specimen of ''Microraptor gui'', on display at the [[Paleozoological Museum of China]].
| regnum = [[Animal]]ia
| phylum = [[Chordate|Chordata]]
| classis = [[Reptile|Sauropsida]]
| superordo = [[Dinosaur]]ia
| ordo = [[Saurischia]]
| subordo = [[Theropoda]]
| familia = [[Dromaeosauridae]]
| subfamilia = [[Microraptorinae]]
| genus = '''''Microraptor'''''
| genus_authority = [[Xu Xing|Xu]] ''et al'', 2000
| subdivision_ranks = [[Species]]
| subdivision =
* ''M. zhaoianus'' ([[type species|type]])
* ''M. gui'' <small>[[Xu Xing|Xu]] ''et al'', 2003</small>
}}
'''''Microraptor''''' ("small thief") is a [[genus]] of small, [[dromaeosaurid]] [[dinosaur]]. About two dozen well-preserved fossil specimens have been recovered from [[Liaoning]], [[China]]. They date from the early [[Cretaceous]] [[Period (geology)|Period]] ([[Barremian]] stage), 130-125.5 [[million years ago]]. Two species have been named, ''M. zhaoianus'' and ''M. gui''. It has recently been suggested that all of the specimens belong to a single species, which is properly called ''M. zhaoianus''. ''[[Cryptovolans]]'', another four-winged dromaeosaur, may also be a species of ''Microraptor''.<ref name="senteretal2004">Senter, P., Barsold, R., Britt, B.B., and Burnham, D.A. (2004). "Systematics and evolution of Dromaeosauridae (Dinosauria, Theropoda)." ''Bulletin of the Gunma Museum of Natural History'', '''8''': 1-20.</ref>
Like ''[[Archaeopteryx]]'', Microraptor provides important evidence about the evolutionary relationship between [[bird]]s and dinosaurs. Microraptor had long [[pennaceous feather]]s that form wing-like surfaces on the arms and tail but also, surprisingly, on the legs. This led Xu (2003) to describe it as a "four winged dinosaur", and to speculate that it may have glided using all four limbs for lift.
== Description ==
[[Image:Microraptor zhaoianus.JPG|left|thumb|''Microraptor zhaoianus'' fossil displayed in [[Hong Kong Science Museum]].]]
At 55-77 [[centimetre|centimeters]] (1.8-2.5 [[foot (unit of length)|ft]]) long from its nose to the tip of its tail, ''Microraptor'' was among the [[Dinosaur size|smallest known dinosaurs]]. Aside from its extremely small size, ''Microraptor'' was among the first non-[[Bird|avian]] dinosaurs discovered with the impressions of feathers and wings. Three specimens of ''M. zhaoianus'' have been described in detail, in addition to six specimens of ''M. gui'' described by Xu ''et al.'' in 2003, 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 its feet as well as its forearms and hands. 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]]. Bands of dark and light present on some specimens may indicate color patterns present in life. 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 [[troodontid]]s. ''Microraptor'' is particularly similar to the basal troodontid ''[[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 [[deinonychosauria]]n split between dromaeosaurids and troodontids.<ref name="hwangetal2002">Hwang, S.H., Norell, M.A., Ji, Q., and Gao, K. (2002). "New Specimens of ''Microraptor zhaoianus'' (Theropoda: Dromaeosauridae) from Northeastern China." ''American Museum Novitates'', 3381: 44pp.[http://research.amnh.org/%7Esunny/hwang.et.al.2002.pdf]</ref>
==Paleobiology==
=== Wings ===
[[Image:Amnh30.jpg|thumb|right|Model of a gliding ''Microraptor gui'']]
''Microraptor'' had two sets of wings, on both its fore- and hind legs. The long feathers on the legs of ''Microraptor'' were true flight feathers as seen in modern [[bird]]s, with asymmetrical vanes on the arm, leg, and tail feathers. As in 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 hind legs, with flight feathers anchored to the upper foot bones as well as the upper and lower leg. It had been proposed by Chinese scientists that the animal glided, and probably lived in trees, pointing to the fact that wings anchored to the feet of ''Microraptor'' would have hindered their ability to run on the ground, and suggest that all primitive dromaeosaurids may have been arboreal.<ref name="Xuetal2003">Xu, X., Zhou, Z., Wang, X., Kuang, X., Zhang, F. and Du, X. (2003). "Four-winged dinosaurs from China." ''Nature'', '''421'''(6921): 335-340, 23 Jan 2003.</ref>
[[Sankar Chatterjee]] determined in 2005 that, in order for the creature to glide or fly, the wings must have been split-level (like a [[biplane]]) and not overlayed (like a [[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]]'' 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 structure, like those on the tibia and the tail, could have been used to control drag and alter the flight path, trajectory, etc. The orientation of the hind wings would also have helped the animal control its gliding flight. Chatterjee also used computer algorithms that test animal flight capacity to test whether or not ''Microraptor'' was capable of true, powered flight, 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 on occasion in addition to gliding.<ref name="chatterjee2007">Chatterjee, S., and Templin, R.J. (2007). "Biplane wing planform and flight performance of the feathered dinosaur ''Microraptor gui''." ''Proceedings of the National Academy of Sciences'', '''104'''(5): 1576-1580. [http://www.pnas.org/cgi/reprint/0609975104v1.pdf]</ref>
===Ground movement===
[[Image:Microraptor gui fossil.JPG|thumb|''Microraptor gui'' fossil displayed in Hong Kong Science Museum.]]
Some paleontologists have suggested that feathered dinosaurs used their wings to parachute from trees, possibly in order to attack or ambush prey on the ground, as a precursor to gliding or true flight. 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.
Chatterjee and Templin also ruled out the possibility of a ground-based takeoff. ''Microraptor'' lacked the necessary adaptations in its shoulder joint to lift its front wings high enough vertically to generate lift from the ground, and the authors argued that a ground-based takeoff would have damaged flight feathers on the feet. This leaves only the possibility of launching from an elevated perch, and the authors noted that even modern birds do not need to use excess power when launching from trees, but use the downward-swooping technique they found in ''Microraptor''.<ref name="chatterjee2007"/>
===Implications===
The unique wing arrangement found in ''Microraptor'' raised the question of its importance to the origin of flight in modern birds--did avian flight go through a four-winged stage, or were four-winged gliders like ''Microraptor'' an evolutionary side-branch that did not leave descendants? As early as 1915, some scientists had argued that the evolution of bird flight may have gone through a four-winged (or ''tetrapteryx'') stage.<ref name="beebe1915">Beebe, C. W. A. (1915). "Tetrapteryx stage in the ancestry of birds." ''Zoologica'', '''2''': 38-52.</ref> 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'', and some modern birds such as raptors, as well as the discovery of ''[[Pedopenna]]'' (another dinosaur with long primary feathers on its feet), 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.<ref name="chatterjee2007"/>
== Naming ==
{{main|Archaeoraptor}}
The naming of ''Microraptor'' is 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 unrelated feathered dinosaur species assembled from multiple specimens in China and smuggled to the USA for sale. After the forgery was revealed by [[Xu Xing]] of [[Beijing]]'s [[Institute of Vertebrate Paleontology and Paleoanthropology]], [[Storrs L. Olson]], curator of birds in the [[National Museum of Natural History]] of the [[Smithsonian Institution]], published a description of the 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.<ref name="olson2000">Olson, S.L. (2000). "Countdown to Piltdown at ''National Geographic'': the rise and fall of ''Archaeoraptor''." ''Backbone'', '''13'''(2) (April): 1–3.</ref> However, Xu had discovered the remainder 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''.<ref name="Xu2000">Xu, X., Zhou, Z., and Wang, X. (2000). "The smallest known non-avian theropod dinosaur." ''Nature'', '''408''' (December): 705-708.[http://research.amnh.org/%7Esunny/microraptor.pdf]</ref>
Since the two names designate the same individual as the [[type specimen]], ''Microraptor zhaoianus'' is a [[junior objective synonym]] of ''Archaeoraptor liaoningensis'' and the latter, if valid, has priority. So, according to some interpretations of the [[International Code of Zoological Nomenclature]], the valid name for this dinosaur probably is ''Archaeoraptor liaoningensis'' Olson 2000. However, there is some doubt whether Olson in fact succeeded in meeting all the formal requirements for establishing a new taxon.
Most paleontologists are unwilling to use the name ''Archaeoraptor'' regardless of the precise legal status of the name. This is firstly because that name is strongly associated with the fraud and the ''National Geographic'' scandal and secondly because they view Olson's use of the name as attempted nomenclatural sabotage and do not want to support it. The name ''Microraptor zhaoianus'' Xu ''et al.'', 2000 has therefore almost attained universal currency.
== Species list ==
So far, six virtually complete skeletons of ''Microraptor'' have been found in [[Liaoning]], [[China]] in 2001 and 2002.
*'''Family: Dromaeosauridae'''
**'''Clade Microraptoria'''
*** '''Genus: ''Microraptor'''''
**** ''Microraptor zhaoianus''
**** ''Microraptor gui''
Note: ''[[Cryptovolans pauli]]'', which has the same four-wing body plan as ''M. gui'', may also be a species of ''Microraptor''. Senter ''et al.'' 2004 found that ''M. zhaoianus'', ''M. gui'', and ''C. pauli'' are all the same species (''M. zhaoianus'').
== In popular culture ==
{{Trivia|date=June 2008}}
*''Microraptor'' featured prominently in the third episode of the 2006 [[mockumentary]] television series ''[[Prehistoric Park]]''. In the episode, ''Microraptor'' were shown flocking down from trees to feast on worms and insects that were brought to the surface by the passage of giant [[titanosaur]]s.
*A ''Microraptor gui'' named [[List of The Land Before Time characters#Guido|Guido]] appeared in the animated film ''[[The Land Before Time XII: The Great Day of the Flyers]]''.
*In the book ''Dinotopia: Journey to Chandara'', the Chandaran Empire, comprising the southeastern portion of the island of [[Dinotopia]], is ruled by the microraptor Emperor Hugo Khan.
*A ''Microraptor'' model was introduced into the [[Carnegie Collection]] in [[2006]].
*Microraptor appeared on a Discovery Channel documentary titled 'The Four Winged Dinosaur' on 22 July 2008
== References ==
{{reflist}}
== External links ==
{{Wikispecies|Microraptor}}
*[http://web.archive.org/web/20040306034207/http://www.indyrad.iupui.edu/public/jrafert/Filipovic/newfeather/Microraptor-gui-(Cryptovol.jpg A model of ''Microraptor''/Cryptovolans pauli by Boban Filipovic]
*Jacqui Hayes: [http://www.cosmosmagazine.com/node/984 Bird wings evolved from biplane dinosaurs] COSMOS magazine
*[http://www.pbs.org/wgbh/nova/microraptor/ PBS Nova program about the Microraptor]
{{portalpar|Dinosaurs}}
[[Category:Cretaceous dinosaurs]]
[[Category:Dromaeosaurs]]
[[Category:Dinosaurs of Asia]]
[[Category:Feathered dinosaurs]]
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