Microraptoria (Greek, μίκρος, ''mīkros'': "small"; Latin, ''raptor'': "one who seizes") is a clade of basal

dromaeosaurid Dromaeosauridae () is a family of feathered theropod dinosaurs. They were generally small to medium-sized feathered carnivores that flourished in the Cretaceous Period. The name Dromaeosauridae means 'running lizards', from Greek ('), meaning ...

theropod Theropoda (; ), whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three toes and claws on each limb. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally ...

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

s. The first microraptorians appeared 125 million years ago in China. Many are known for long feathers on their legs and may have been semi

arboreal Arboreal locomotion is the locomotion of animals in trees. In habitats in which trees are present, animals have evolved to move in them. Some animals may scale trees only occasionally, but others are exclusively arboreal. The habitats pose num ...

powered fliers, some of which were even capable of launching from the ground.. Most microraptorians were relatively small; adult specimens of ''

Microraptor ''Microraptor'' (Greek, μικρός, ''mīkros'': "small"; Latin, ''raptor'': "one who seizes") is a genus of small, four-winged dromaeosaurid dinosaurs. Numerous well-preserved fossil specimens have been recovered from Liaoning, China. They dat ...

'' range between ) and weigh up to , making them some of the smallest known nonavialan dinosaurs.Holtz, Thomas R. Jr. (2011) ''Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages,'
Winter 2010 Appendix.
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Description

Microraptorians were a group of basal dromaeosaurids (popularly known as "raptors") with slender proportions and long limbs. With the exception of '' Hesperonychus'' from the late

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...

of North America, all microraptorians have been found in the Yixian and Jifuotang Formations of Liaoning County, China, hence why microraptorians are sometimes referred to as "Liaoning dromaeosaurs". These formations (collectively known as the Jehol group) have been dated to the early Cretaceous and at that time would have been part of a temperate wetland ecosystem threatened by frequent volcanic eruptions. Like other dromaeosaurids, microraptorians were carnivores with relatively large, serrated teeth and a hyperextendable second toe equipped with a curved claw.

Size and proportions

Most microraptorians were small dinosaurs, with taxa such as ''

'' and especially '' Zhongjianosaurus'' being among the smallest nonavian dinosaurs known. However, some microraptorians, such as '' Tianyuraptor'' and '' Changyuraptor'', were larger and similar to other dromaeosaurids in size. Many microraptorians also had long and robust arms and legs, in contrast to the stockier eudromaeosaurs, although long arms are not universal to the group, since the basal microraptorian ''Tianyuraptor'' had unusually short arms by dromaeosaurid standards. Considering this, the small size and long wings of some microraptorians likely are examples of convergent evolution with other small

paravians Paraves are a widespread group of theropod dinosaurs that originated in the Middle Jurassic period. In addition to the extinct dromaeosaurids, troodontids, anchiornithids, and possibly the scansoriopterygids, the group also contains the avia ...

and early birds such as ''

Anchiornis ''Anchiornis'' is a genus of small, four-winged paravian dinosaurs, with only one known species, the type species ''Anchiornis huxleyi'', named for its similarity to modern birds. The Latin name ''Anchiornis'' derives from a Greek word meaning "n ...

'' and ''

Archaeopteryx ''Archaeopteryx'' (; ), sometimes referred to by its German name, "" ( ''Primeval Bird''), is a genus of bird-like dinosaurs. The name derives from the ancient Greek (''archaīos''), meaning "ancient", and (''ptéryx''), meaning "feather" ...

''.

Feathers

The fossilization conditions of the Jehol group are very accommodating to the preservation of soft structures in fossils, and as a result, many microraptorians have been preserved with a covering of feathers. Not only have long, advanced feathers been preserved on the arms and tails of many specimens, but a few species even have long feathers on their legs. This condition has also been seen in other paravians such as ''Anchiornis'', and has caused these kinds of dinosaurs to be labelled as "four-winged dinosaurs". The largest known "four-winged" dinosaur, '' Changyuraptor,'' is a microraptorian. Some microraptorians such as ''

'' possibly were able to use these wings to glide or take off from the ground.

Characteristic features

Microraptorines can be distinguished from other dromaeosaurids by these features: * A

maxilla The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The ...

laterally sculpted by small pits * A very short manual

phalanx The phalanx ( grc, φάλαγξ; plural phalanxes or phalanges, , ) was a rectangular mass military formation, usually composed entirely of heavy infantry armed with spears, pikes, sarissas, or similar pole weapons. The term is particular ...

III-2 * A shortened first digit of the hand * A splatulate (rounded)

pubic symphysis The pubic symphysis is a secondary cartilaginous joint between the left and right superior rami of the pubis of the hip bones. It is in front of and below the urinary bladder. In males, the suspensory ligament of the penis attaches to the pubi ...

* A

metatarsal The metatarsal bones, or metatarsus, are a group of five long bones in the foot, located between the tarsal bones of the hind- and mid-foot and the phalanges of the toes. Lacking individual names, the metatarsal bones are numbered from the med ...

III with a pinched proximal end * A slender metatarsal II In addition, several features are present in microraptorines with the exception of ''Tianyuraptor'', which is believed to be a basal member of the clade: * A large oval fenestra in the

coracoid A coracoid (from Greek κόραξ, ''koraks'', raven) is a paired bone which is part of the shoulder assembly in all vertebrates except therian mammals (marsupials and placentals). In therian mammals (including humans), a coracoid process is pre ...

* Significantly shortened penultimate manual phalanges * The posterior end of the

ilium Ilium or Ileum may refer to: Places and jurisdictions * Ilion (Asia Minor), former name of Troy * Ilium (Epirus), an ancient city in Epirus, Greece * Ilium, ancient name of Cestria (Epirus), an ancient city in Epirus, Greece * Ilium Building, a ...

extending ventral to the ischial peduncle * Lateral projections halfway down the pubis * A strongly anteriorly curved pubic shaft

Classification

Microraptoria is usually classified as a clade of dromaeosaurids. Senter and colleagues expressly coined the name without the subfamily suffix ''-inae'' to avoid perceived issues with erecting a

traditional A tradition is a belief or behavior (folk custom) passed down within a group or society with symbolic meaning or special significance with origins in the past. A component of cultural expressions and folklore, common examples include holidays ...

family-group taxon, should the group be found to lie outside the Dromaeosauridae proper. Sereno offered a revised definition of the subgroup containing ''Microraptor'' to ensure that it would fall within the 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.Sereno, P. C. 2005
Stem Archosauria—TaxonSearch
[version 1.0, November 7, 2005 The cladogram below follows a 2012 analysis by paleontologists Phil Senter, James I. Kirkland, Donald D. DeBlieux, Scott Madsen and Natalie Toth.

References

*"Expand and Life history of a basal bird: morphometrics of the Early Cretaceous Confuciusornis" Luis M Chiappe, Jesús Marugán-Lobón, Shu'an Ji & Zhonghe Zhou (2008)

External links

*1.http://www.paleodb.org/cgi-bin/bridge.pl?a=basicTaxonInfo&taxon_no=143267 *2.http://www.taxonsearch.org/dev/taxon_edit.php?tax_id=483&Action=View *3.http://theropoddatabase.blogspot.com/2010/03/article-1311-means-lewisuchinaeidae-is.html {{Taxonbar, from=Q3312288 Dromaeosaurs