Microraptoria (Greek, μίκρος, mīkros: "small"; Latin, raptor: "one who seizes") is a clade of basal dromaeosaurid theropod dinosaurs. 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 powered fliers, some of which even capable of launching from the ground. Most microraptorians were relatively small; adult specimens of Microraptor range between 77–90 centimetres long (2.53–2.95 ft) and weigh up to 1 kilogram (2.2 lb), making them some of the smallest known dinosaurs.
Temporal range: 125–76.5 Ma
|Fossil specimen of a Microraptor, with white arrows pointing at preserved feathers|
Senter et al., 2004
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 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 an hyper-extendable second toe equipped with a curved claw.
Most microraptorians were small dinosaurs, with taxa like Microraptor and especially Zhongjianosaurus being among the smallest non-avian 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, it is likely that the small size and long wings of some microraptorians are an example of convergent evolution with other small paravians and early birds such as Anchiornis and Archaeopteryx.
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. It is possible that some microraptorians such as Microraptor were able to use these wings to glide or take off from the ground.
Microraptorines can be distinguished from other dromaeosaurids due to the following features:
In addition, several features are present in microraptorines with the exception of Tianyuraptor, which is believed to be a basal member of the clade:
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 family-group taxon, should the group be found to lie outside Dromaeosauridae proper. Sereno offered a revised definition of the sub-group containing Microraptor to ensure that it would fall within 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.
The cladogram below follows a 2012 analysis by paleontologists Phil Senter, James I. Kirkland, Donald D. DeBlieux, Scott Madsen and Natalie Toth.
Acheroraptor is an extinct genus of dromaeosaurid theropod dinosaur known from the latest Maastrichtian Hell Creek Formation of Montana, United States. It contains a single species, Acheroraptor temertyorum. A. temertyorum is one of the two geologically youngest known species of dromaeosaurids, the other being Dakotaraptor, which is also known from Hell Creek.Changyuraptor
Changyuraptor is a genus of "four-winged", predatory dinosaurs. It is known from a single fossil specimen representing the species Changyuraptor yangi, which was discovered from Early Cretaceous (125 million year old) deposits in Liaoning Province, China. C. yangi belongs to the group of dromaeosaurid theropod dinosaurs called the Microraptoria.At the time of its discovery, C. yangi was the largest four-winged dinosaur known and among the largest Mesozoic flying paravians, volant true birds seldom approaching its size.Dromaeosaurinae
Dromaeosaurinae is a subfamily of Dromaeosauridae. Most dromaeosaurines lived in what is now the United States and Canada, as well as Mongolia, and possibly Denmark as well. Isolated teeth that may belong to African dromaeosaurines have also been discovered in Ethiopia. These teeth date to the Tithonian stage, of the Late Jurassic Period.All North American and Asian dromaeosaurine dinosaurs from the Late Cretaceous were generally small, no more than 1.8 metres (5.9 ft) long, in Dromaeosaurus and Adasaurus. However, among the dromaeosaurines were the largest dromaeosaurs ever; Dakotaraptor was ~5.5 metres (18 ft) long, Achillobator 6 metres (20 ft), and Utahraptor up to ~7 metres (23 ft).Eudromaeosauria
Eudromaeosauria ("true dromaeosaurs") is a subgroup of terrestrial dromaeosaurid theropod dinosaurs. They were relatively large-bodied, feathered hypercarnivores (with diets consisting almost entirely of other terrestrial vertebrates) that flourished in the Cretaceous Period.
Eudromaeosaur fossils are known almost exclusively from the northern hemisphere. They first appeared in the early Cretaceous Period (early Aptian stage, about 124 million years ago) and survived until the end of the Cretaceous (Maastrichtian stage, 66 Ma). The earliest known definitive eudromaeosaur is the dromaeosaurine Utahraptor ostrommaysorum, from the Cedar Mountain Formation, dated to 124 million years ago. However, the earlier (143-million-year-old) fossils such as those of Nuthetes destructor and several indeterminate teeth dating to the Kimmeridgian stage may represent eudromaeosaurs.Graciliraptor
Graciliraptor (meaning "graceful thief") is a genus of theropod dinosaur from the early Cretaceous Period. It is a microraptorine dromaeosaurid.
The type species Graciliraptor lujiatunensis was first named and described in 2004 by Xu Xing and Wang Xiaoling. The generic name is derived from Latin gracilis and raptor. The specific name refers to the village Lujiatun where the fossil site is located. Its fossil, holotype IVPP V 13474, was found in Beipiao, Liaoning Province, China.Halszkaraptorinae
Halszkaraptorinae is a basal ("primitive") subfamily of Dromaeosauridae that includes the enigmatic genera Halszkaraptor, Mahakala, and Hulsanpes. A comparison of the fossils of Halszkaraptor with the bones of extant crocodilians and aquatic birds revealed evidence of a semiaquatic lifestyle. The group is named after Polish paleontologist Halszka Osmólska.Hesperonychus
Hesperonychus (meaning "western claw") was a genus of small, carnivorous dromaeosaurid dinosaur. There is one described species, Hesperonychus elizabethae; the type species was named in honor of the woman who collected it in 1982. It is known from fossils recovered from the lowermost strata of the Dinosaur Park Formation of Alberta, dating to the late Cretaceous Period (Campanian stage) about 76.5 million years ago).
Hesperonychus is known from one partial pelvic girdle, holotype specimen UALVP 48778, collected by Dr. Elizabeth Nicholls in Dinosaur Provincial Park in 1982. The fossil remained undescribed, however, until Nick Longrich and Phil Currie published on it in 2009. A number of very small toe bones, including "sickle claws", in the collection of the Royal Tyrrell Museum may also belong to Hesperonychus. The gracile appearance of these toe bones makes it unlikely that they belonged to a member of Eudromaeosauria. Despite their small size, the pubic bones were fused, a characteristic of adult dinosaurs, indicating that the specimen does not represent a juvenile of a known species.Though known from only partial remains, Longrich and Currie estimated its total length at under one meter and weight at about 1.9 kilograms, making it one of the smallest known carnivorous dinosaurs from North America. The alvarezsaurid Albertonykus was smaller.Hulsanpes
Hulsanpes is a genus of dromaeosaurid theropod dinosaur from Mongolia that lived during the Late Cretaceous.Itemirus
Itemirus is a genus of theropod dinosaur from the Turonian age of the Late Cretaceous period of Uzbekistan.Luanchuanraptor
Luanchuanraptor (meaning "Luanchuan thief") is a genus of dromaeosaurid theropod dinosaur from the Late Cretaceous of China. It is based on a partial skeleton from the Qiupa Formation in Luanchuan, Henan. A medium-sized dromaeosaurid, it is the first Asian dromaeosaurid described from outside the Gobi Desert or northeastern China. The fossil material is cataloged as 4HIII-0100 in the Henan Geological Museum and includes four teeth, one frontal, a neck vertebra, one or two back vertebrae, seventeen tail vertebrae, ribs, chevrons, a humerus (upper arm bone), claw and finger bones, partial shoulder and pelvic girdles, and other fragmentary bones from a moderately sized dromaeosaurid. The type species is L. henanensis, described by Lü et al. in 2007.Mahakala omnogovae
Mahakala (from Sanskrit, named for Mahakala, one of eight protector deities (dharmapalas) in Tibetan Buddhism) is a genus of basal dromaeosaurid dinosaur from the Campanian-age (about 80 million years ago) Upper Cretaceous Djadokhta Formation of Ömnögovi, Mongolia. It is based on a partial skeleton found in the Gobi Desert. Mahakala was a small dromaeosaurid (approximately 70 centimeters long (28 in)), and its skeleton shows features that are also found in early troodontids and avialans. Despite its late appearance, it is among the most basal dromaeosaurids. Its small size, and the small size of other basal deinonychosaurians, suggests that small size appeared before flight capability in birds.Pamparaptor
Pamparaptor is an extinct genus of carnivorous deinonychosaur from the late Cretaceous period. It is a basal dromaeosaurid dinosaur with troodontid-like pes which lived during the late Cretaceous period (Turonian to Coniacian stage) in what is now Neuquén province, Patagonia, Argentina. It is known from the holotype MUCPv-1163, an articulated and nearly complete left foot.
The specimen recovered from the Portezuelo Formation (Río Neuquén Subgroup) of Neuquén Group. It was initially considered to be a juvenile specimen of another dromaeosaurid species, Neuquenraptor argentinus. However, it was later re-interpreted as a new genus and named Pamparaptor by Juan D. Porfiri, Jorge O. Calvo and Domenica dos Santos in 2011 and the type species is Pamparaptor micros. The generic name honors Indian Pampas people who lived in central Argentina while "raptor" (robber in Latin). The specific name (micros, meaning "small") refers to the specimen's size (estimated at 0.5 to 0.7 metres (1.6 to 2.3 ft) in length).Pyroraptor
Pyroraptor (meaning "fire thief") is a genus of dromaeosaurid dinosaur from the Late Cretaceous of what is now southern France, it lived during the late Campanian and early Maastrichtian stages, approximately 70.6 million years ago. It is known from a single partial specimen that was found in Provence in 1992. The animal was named Pyroraptor olympius by Allain and Taquet in 2000.Saurornitholestinae
Saurornitholestinae is a subfamily of dromaeosaurid dinosaurs. The saurornitholestines currently include three monotypic genera: Atrociraptor marshalli, Bambiraptor feinbergorum, and Saurornitholestes langstoni. All are medium-sized dromaeosaurs from the Late Cretaceous of western North America. The group was originally recognized by Longrich and Currie as the sister taxon to a clade formed by the Dromaeosaurinae and Velociraptorinae. However, not all phylogenetic analyses recover this group.Unenlagiinae
Unenlagiinae is a subfamily of dromaeosaurid theropods. Unenlagiines are known from South America and Antarctica.Unquillosaurus
Unquillosaurus (meaning "Unquillo river lizard") is a genus of maniraptoran dinosaur from the Late Cretaceous Period, discovered in Argentina. Known only from a single fossilized pubis (a pelvic bone), its total body length may have reached 2 to 3 metres (6.6 to 9.8 ft).Variraptor
Variraptor ( VARR-i-rap-tor; "Var thief") is a genus of coelurosaurian theropod dinosaur from the Late Cretaceous of France.Yurgovuchia
Yurgovuchia is an extinct genus of dromaeosaurid theropod dinosaur known from the Early Cretaceous (probably Barremian stage) of Utah. It contains a single species, Yurgovuchia doellingi. According to a phylogenetic analysis performed by its describers, it represents an advanced dromaeosaurine, closely related to Achillobator, Dromaeosaurus and Utahraptor.Zhongjianosaurus
Zhongjianosaurus is a genus of dromaeosaurid belonging to the Microraptoria. Believed to hail from the Yixian Formation, specifically the middle of the Jehol Biota, it is the smallest known microraptorine thus far discovered and one of the smallest non-avian theropod dinosaurs.