This amazing picture of Microraptor/Cryptovolans pauli was made by Boban Filipovic. I would like to thank him once more for his friendly allowance to show some of his works here! Notice how the animal appears to be pursueing some prey in that thicket!
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Description: Microraptoria were small, gracile animals. The length estimations I found so far are 77 cm for Microraptor gui (Xu et al. 2003) and 55 cm for Microraptor zhaoianus (Hwang et al. 2002). No weight estimations are available to me at this time, but taking into consideration their likely ability to glide or even fly, I would think that a few hundred grams (for the possibly more arboreal (living in trees) adapted forms such as Microraptor zhaoianus, Microraptor gui and Microraptor/Cryptovolans pauli) and maybe one or two kilogramms (for the possibly more cursorial (running on the ground) adapted forms such as Sinornithosaurus millenii and (possibly) Graciliraptor lujiatunensis) seem likely. While the appearance of other Deinonychosauria is very bird-like, that of the Microraptoria is propably best described as incredibly bird-like.

The heads of Microraptoria included slightly elongated as well as compact, a bit triangular shapes.

Head of Sinornithosaurus millenii (slightly elongated).Head of Microraptor zhaoianus (compact/triangular)
Sinornithosaurus millenii. The neck is a bit shorter then in Dromaeosauridae. Note the stiffened tail! Since both Microraptoria and Dromaeosauridae show the elongated prezygapophyses and chevrons (see Dromaeosauridae-page) the former often plot together with the latter in cladogramms. Besides this one Microraptoria and Dromaeosauridae show a large number of shared characters (see below) which explains why not all authors agree with Microraptoria as a family of its own yet. Also note the very avian (bird) -like folding of the arm/wing.
The body shape of the Microraptoria is similar to that of most theropods, possibly a bit more flattened/streamlined in some species, which may be interpreted as an adaption towards gliding.
Microraptoria possessed long arms and legs. While pennaceaous feathers (modern, asymmetrical feathers, interpreted by many authors as an adaption towards flight) were present on the arms of all Microraptoria and at least some (possibly all) Dromaeosauridae (they may have served for display in the latter family), this advanced type of feathers is also present on the legs and tails of Microraptor zhaoianus, Microraptor gui and (possibly) Microraptor/Cryptovolans pauli (Norell & Xu 2005).
Microraptor/Cryptovolans pauli. Note the difference between the pennaceous feathers on the arms/wings , legs and tail in contrast to the more plumulaceous (body-covering feathers which served the animal as insulation) ones covering the body. Also note that the legs/hindwings point downwards in an inverted V-shape. In the media Microraptor gui often got depicted with all four wings stretched out to both sides. To take up such a pose was certainly impossible for the animal since stretching the legs/hindwings fully to the sides would have required the femurs's heads to pop out of their sockets! Thus the hindwings of these animals propably only partially served as airfoils! I think it is likely that the hindwings mainly served as rudders, just as the V-shaped rudders seen on some modern airplanes (partially based on Thomas R. Holtz, Jr., see archives of the DML 22. Jan. 2003).
Right hand of Microraptor/Cryptovolans pauli. Finger 3 is a bit hard to spot because some feathers are in the way. While a good portion of finger 1 is visible only the claws of fingers 2 and 3 are, because they are covered by the feathers.
Although not as much enlarged as in Dromaeosauridae, the feet of the Microraptoria also possessed the typical predatory claw on each of the second toes. Toe number one was reduced and displaced towards the rear and upwards.
Right foot of Microraptor/Cryptovolans pauli. Due to it's positioning toe 1 is not visible in this picture. Note the predatory claw on toe 2.
History: The first find of a member of the Microraptoria was Sinornithosaurus milenii described in 1999 by Xu, Wang and Wu. Microraptoria as a family was first established in 2004 by Senter et al. (see "The Theropod Database" under "Links"). Cryptovolans pauli deserves special mention concerning it's nameing: Since this member of the Microraptoria shows many similarities to Microraptor, it's name may possibly change to Microraptor pauli in the near future. Until now Microraptoria are only known from China's early Cretaceous deposits.
The theropod-bird link: Since it's first proposal by Gegenbauer in 1862 the evolution of birds originating from the non-avian dinosaurs has been the subject of many (at times quite heated) discussions among scientists. I would like to quote one of my favorite authors on the subject, Paul C. Sereno. Here is what he wrote in the abstract (short summary) of his 2004 publication "Birds as dinosaurs" which can be download in .pdf format from the Acta Zoologica Sinica (my comments in brackets):

"The 'great debate' over bird origins may never have transpired had the now-famous furcula-(whishbone)-bearing, feathered dinosaurs from Asia surfaced when the beds in which they were interred were first discovered in the 1920s. Compelling fossil evidence is now to hand that places birds as a specialized clade (group of animals) within theropod dinosaurs. Major insights include a more seamless fossil record linking birds and non-avian dinosaurs, clear evidence of an early pre-avian origin for feathers and other features previously known only among birds, together with an underscoring of the importance of miniaturization for the evolution of powered flight and a broadening of the functional scenarios for how powered flight was first achieved."

Since Boban Filipovic (who is a student of palaeontoloy at the university of Belgrade and manufactured the magnificent models of Microraptoria based on skeletal reconstructions and also took the photos of his models in life-like postures) convinced me that the complexity of the whole theropod-origin-of-birds - subject actually deserves a page of it's own, I would like to stop here and include yet one more page into this website. Instead of including the link to that page into the main menu I choose to have it here in the text because like this I wont have to restructure all the pages I have done so far once again.
Klick here to view the page solely dedicated to the theropod-bird-link!
Habits: Only a few studies on the Microraptoria have been published so far. Much remains to be learned about these little beauties and only very little can be said at this time about

Microraptor zhaoianus. This picture shows very nicely how some Microraptoria may have used their claws in order to climb trees. how they may actually have behaved. However, I will try to describe a few inferences scientists have made so far based on
their studies of the Microraptoria and other feathered non-avian dinosaurs. First of all it seems likely that some Microraptoria (Microraptor zhaoianus, Microraptor gui and Microraptor/Cryptovolans pauli) led mostly arboreal (tree-based) lifes (Xu et al. 2003). Moreover at least the species named above were able to glide (Xu et al. 2003). Wether this ability to glide was aquired "from the trees down" or "from the ground up" is very hard to tell. While both hypotheses have very strong points speaking for them, the "from the ground up"-hypothesis has one significant advantage: The fossil record! Theropod fossils have been found that show these animals in several "snapshots in time" depicting them in typical bird-like poses. Mei long was found sleeping on the ground with it's head tucked in under a "wing" extremly similar to the sleeping posture seen in modern avian dinosaurs (birds) (Xu et al. 2004). Oviraptor philoceratops was found when brooding it's eggs in the same manner as modern avian dinosaurs do (Norell et al. 1995). These finds indicate that theropods displayed behaviours usually associated with modern avian dinosaurs (birds). But theropods are widely accepted to have led ground-based lifes! While there can be little doubt that Microraptoria were possibly well adapted towards an arboreal lifestyle, they do not represent the most early stages in the development of powered flight. Many authors (for example Carpenter 2002) have shown that many theropods in general and specially Deinonychosauria were able to perform (at least limited) flapping-like movements with their arms. Thus it may be very well possible that (contrary to what our intuition may tell us) the most early stages in the develoment of powered flight occured "from the ground up" when Deinonychosauria (who were pre-adapted for flight because they possessed the long arms equipped with feathers of modern type, the anatomical structures that allowed them to move their arms in the required manner and the speed-capabilities) may have almost accidentally made their first leaps toward what should become a main feature for most of their heirs: Flight. For a more elaborate presentation of both hypotheses please see "How did dinosaurs begin to fly?" by Sankar Chatterjee & R. Jack Templin (for the "from the trees down" hypothesis) and Luis M. Chiappe (for the "from the ground up" hypothesis) in Natural History, May 2005, pages 54 - 55. Teeth and claws of the Microraptoria clearly identify them as carnivores, but what made up for the most part of their diet is not known so far. The Yixian and Jiufotang Formations have yielded a variety of small vertebrate-fossils so far amongst them fish, lizards, turtles, birds and at least one small mammal (Wang et al. 1999). So there were a lot of possible vertebrate prey-animals around (not to mention the propably even more abundant non-vertebrates!), but as said before I couldnt find any mention of fossil evidence for any sort of "prey-preferances" for the Microraptoria in the litarature available to me so far.
A lot of possible behaviours and habits are thinkable to have occured in the Microraptoria, but until further studies are published, we all will have to show some patience.