Microraptoria (Greek, μίκρος, ''mīkros'': "small"; Latin, ''raptor'': "one who seizes") is a
clade
In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...
of basal
dromaeosaurid
Dromaeosauridae () is a family (biology), family of feathered coelurosaurian Theropoda, theropod dinosaurs. They were generally small to medium-sized feathered carnivores that flourished in the Cretaceous period (geology), Period. The name Drom ...
theropod
Theropoda (; from ancient Greek , (''therion'') "wild beast"; , (''pous, podos'') "foot"">wiktionary:ποδός"> (''pous, podos'') "foot" is one of the three major groups (clades) of dinosaurs, alongside Ornithischia and Sauropodom ...
dinosaur
Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic Geological period, period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the #Evolutio ...
s. Definitive microraptorians lived during the
Barremian
The Barremian is an age in the geologic timescale (or a chronostratigraphic stage) between 125.77 Ma (million years ago) and 121.4 ± 1.0 Ma (Historically, this stage was placed at 129.4 million to approximately 125 million years ago) It is a ...
to
Aptian
The Aptian is an age (geology), age in the geologic timescale or a stage (stratigraphy), stage in the stratigraphic column. It is a subdivision of the Early Cretaceous, Early or Lower Cretaceous epoch (geology), Epoch or series (stratigraphy), S ...
stages of the
Early Cretaceous
The Early Cretaceous (geochronology, geochronological name) or the Lower Cretaceous (chronostratigraphy, chronostratigraphic name) is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 143.1 ...
in
China
China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...
. Probable microraptorian ichnotaxon ''
Dromaeosauriformipes'' was discovered from the
Jinju Formation of
South Korea
South Korea, officially the Republic of Korea (ROK), is a country in East Asia. It constitutes the southern half of the Korea, Korean Peninsula and borders North Korea along the Korean Demilitarized Zone, with the Yellow Sea to the west and t ...
, and some fragmentary
Late Cretaceous
The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''cre ...
paravian fossils in
North America
North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...
have been described as putative members of this clade. Many are known for long feathers on their legs and may have been
semiarboreal powered fliers, some of which were even capable of launching from the ground.
[.] Most microraptorians were relatively small; adult specimens of ''
Microraptor
''Microraptor'' (Greek language, Greek, μικρός, ''mīkros'': "small"; Latin language, Latin, ''raptor'': "one who seizes") is a genus of small, four-winged dromaeosaurid dinosaurs. Numerous well-preserved fossil specimens have been recovere ...
'' range between ) and weigh up to , making them some of the
smallest known non-avialan dinosaurs.
[Holtz, Thomas R. Jr. (2011) ''Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages,']
Winter 2010 Appendix.
/ref>
Description
Microraptorians were a group of basal dromaeosaurids (popularly known as "raptors") with slender proportions and long limbs. All definitive members have been found in the Yixian and Jifuotang Formations of Liaoning County of China, so they're referred to as "Liaoning dromaeosaurids" by some researchers. These formations (collectively known as the Jehol Biota
The Jehol Biota includes all the living organisms – the ecosystem – of northeastern China between 133 and 120 million years ago. This is the Lower Cretaceous ecosystem which left fossils in the Yixian Formation and Jiufotang Formation. These d ...
) 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. Some fragmentary paravian fossils from the Late Cretaceous
The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''cre ...
(Campanian
The Campanian is the fifth of six ages of the Late Cretaceous epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campa ...
-Maastrichtian
The Maastrichtian ( ) is, in the International Commission on Stratigraphy (ICS) geologic timescale, the latest age (geology), age (uppermost stage (stratigraphy), stage) of the Late Cretaceous epoch (geology), Epoch or Upper Cretaceous series (s ...
stages) of North America have been putatively suggested as microraptorians, though their taxonomic referral are considered controversial, namely '' Hesperonychus'' being recovered as an avialan
Avialae ("bird wings") is a clade containing the only living dinosaurs, the birds, and their closest relatives. It is usually defined as all theropod dinosaurs more closely related to birds (Aves) than to deinonychosaurs, though alternative defi ...
in one phylogenetic analysis.
Size and proportions
Most microraptorians were small dinosaurs, with taxa such as ''Microraptor
''Microraptor'' (Greek language, Greek, μικρός, ''mīkros'': "small"; Latin language, Latin, ''raptor'': "one who seizes") is a genus of small, four-winged dromaeosaurid dinosaurs. Numerous well-preserved fossil specimens have been recovere ...
'' 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 and early birds such as ''Anchiornis
''Anchiornis'' is a genus of small, four-winged Paraves, 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 m ...
'' 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 (''archaîos''), 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 ''Microraptor
''Microraptor'' (Greek language, Greek, μικρός, ''mīkros'': "small"; Latin language, Latin, ''raptor'': "one who seizes") is a genus of small, four-winged dromaeosaurid dinosaurs. Numerous well-preserved fossil specimens have been recovere ...
'' possibly were able to use these wings to glide or take off from the ground, and perhaps even capable of powered flight.
Characteristic features
Sources:
Microraptorines can be distinguished from other dromaeosaurids by these features:
* A maxilla
In vertebrates, the maxilla (: maxillae ) 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 two maxil ...
laterally sculpted by small pits
* A very short manual phalanx
The phalanx (: phalanxes or phalanges) was a rectangular mass military formation, usually composed entirely of heavy infantry armed with spears, pikes, sarissas, or similar polearms tightly packed together. The term is particularly used t ...
III-2
* A shortened first digit of the hand
* A splatulate (rounded) pubic symphysis
The pubic symphysis (: symphyses) 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 attache ...
* A metatarsal
The metatarsal bones or metatarsus (: metatarsi) are a group of five long bones in the midfoot, located between the tarsal bones (which form the heel and the ankle) and the phalanges ( toes). Lacking individual names, the metatarsal bones are ...
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 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 present as part of the scapula, but this is n ...
* Significantly shortened penultimate manual phalanges
* The posterior end of the ilium 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 Dromaeosauridae
Dromaeosauridae () is a family of feathered coelurosaurian theropod dinosaurs. They were generally small to medium-sized feathered carnivores that flourished in the Cretaceous Period. The name Dromaeosauridae means 'running lizards', from ...
, though some consider the group to be outside the dromaeosaurid family. Senter and colleagues expressly coined the name without the subfamily suffix ''-inae'' to avoid perceived issues with erecting a traditional
A tradition is a system of beliefs or behaviors (folk custom) passed down within a group of people or society with symbolic meaning or special significance with origins in the past. A component of cultural expressions and folklore, common examp ...
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.
In a 2024 paper which reported the smallest known juvenile specimen of ''Microraptor'', Wang and Pei included microraptorians and eudromaeosaurians within a new clade Serraraptoria.
See also
* Timeline of dromaeosaurid research
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.https://paleobiodb.org/classic/checkTaxonInfo?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
Dinosaur clades
Early Cretaceous dinosaurs
Dinosaurs of Asia