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iMicroraptor
Fossil range: Early Cretaceous
Amnh30
Model of Microraptor gui at the American Museum of Natural History
Conservation status
Extinct (fossil)
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Sauropsida
Superorder: Dinosauria
Order: Saurischia
Suborder: Theropoda
Infraorder: Deinonychosauria
Family: Dromaeosauridae
Subfamily: Microraptorinae
Genus: Microraptor
Xu et al, 2000
Species
  • M. zhaoianus (type)
  • M. gui Xu et al, 2003

Microraptor ("small thief") was a genus of small, dromaeosaurid dinosaur from the Lower Cretaceous Period (Barremian stage), 130-125.5 million years ago. Like Archaeopteryx, it demonstrates the close evolutionary relationship between birds and dinosaurs, as it had long pennaceous feathers on its limbs and tail. 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.

Description

Microraptor fossil1

A cast of a fossil Microraptor gui with preserved feathers.

Microraptor was 55-77 cm (1.8-2.5 ft) long from its nose to the tip of its tail. Three specimens of M. zhaoianus have been described in detail, in addition to the six specimens of M. gui described by Xu et al. in 2003, from which most feather impressions are known. 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). Some specimens demonstrate a raised feather "crest" on the head, similar to some modern birds, like the Pileated Woodpecker. Bands of dark and light present on some specimens may indicate color patterns present in life. Several anatomical features fond 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. 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 deinonychosaurian split between dromaeosaurids and troodontids.[1]

Wings

Like its close relative Cryptovolans (possibly a junior synonym of Microraptor), Microraptor had two sets of wings, on both its fore- and hind legs (close studies of the Berlin specimen of the primitive bird Archaeopteryx show that it too, had flight feathers on its hind legs, albeit shortened). The long feathers on the legs of Microraptor were true flight feathers as seen in modern birds, with asymetrical 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. Sankar Chatterjee determined in 2005 that, in order for the creature to fly, the wings must have been split-level (like a biplane) and not overlayed (like a dragonfly). It has 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 suggst that all primitive dromaeosaurids may have been arboreal.[2]

Naming

Main article: 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.[3] 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.[4]

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
    • Subamily: 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).

Microraptor in culture

The Microraptor featured prominently in the third episode of Prehistoric Park. They were shown as gliding dinosaurs that were closely related to birds. They flocked down to feast on worms and insects that were bought to the surface by Titanosaurus' footprints.

References

  1. 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.[1]
  2. Xu, X., Zhou, Z., Wang, X., Kuang, X., Zhang, F. and Du, X. (2003). "Four-winged dinosaurs from China." Nature, 421(23): 335-340.[2]
  3. Olson, S.L. (2000). "Countdown to Piltdown at National Geographic: the rise and fall of Archaeoraptor." Backbone, 13(2) (April): 1–3.
  4. Xu, X., Zhou, Z., and Wang, X. (2000). "The smallest known non-avian theropod dinosaur." Nature, 408 (December): 705-708.[3]

External links

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