31-578: Microraptoria (Greek, μίκρος, mīkros : "small"; Latin, raptor : "one who seizes") is a clade of basal dromaeosaurid theropod dinosaurs . Definitive microraptorians lived during the Barremian to Aptian stages of the Early Cretaceous in China . 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
62-588: A population , or a species ( extinct or extant ). Clades are nested, one in another, as each branch in turn splits into smaller branches. These splits reflect evolutionary history as populations diverged and evolved independently. Clades are termed monophyletic (Greek: "one clan") groups. Over the last few decades, the cladistic approach has revolutionized biological classification and revealed surprising evolutionary relationships among organisms. Increasingly, taxonomists try to avoid naming taxa that are not clades; that is, taxa that are not monophyletic . Some of
93-479: A "ladder", with supposedly more "advanced" organisms at the top. Taxonomists have increasingly worked to make the taxonomic system reflect evolution. When it comes to naming , this principle is not always compatible with the traditional rank-based nomenclature (in which only taxa associated with a rank can be named) because not enough ranks exist to name a long series of nested clades. For these and other reasons, phylogenetic nomenclature has been developed; it
124-400: A 2024 paper which reported the smallest known juvenile specimen of Microraptor , Wang and Pei included microraptorians and eudromaeosaurians within a new clade Serraraptoria. [REDACTED] [REDACTED] Clade In biological phylogenetics , a clade (from Ancient Greek κλάδος (kládos) 'branch'), also known as a monophyletic group or natural group , is
155-446: A branch of mammals that split off after the end of the period when the clade Dinosauria stopped being the dominant terrestrial vertebrates 66 million years ago. The original population and all its descendants are a clade. The rodent clade corresponds to the order Rodentia, and insects to the class Insecta. These clades include smaller clades, such as chipmunk or ant , each of which consists of even smaller clades. The clade "rodent"
186-623: A clade can be described based on two different reference points, crown age and stem age. The crown age of a clade refers to the age of the most recent common ancestor of all of the species in the clade. The stem age of a clade refers to the time that the ancestral lineage of the clade diverged from its sister clade. A clade's stem age is either the same as or older than its crown age. Ages of clades cannot be directly observed. They are inferred, either from stratigraphy of fossils , or from molecular clock estimates. Viruses , and particularly RNA viruses form clades. These are useful in tracking
217-543: A grouping of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree . In the taxonomical literature, sometimes the Latin form cladus (plural cladi ) is used rather than the English form. Clades are the fundamental unit of cladistics , a modern approach to taxonomy adopted by most biological fields. The common ancestor may be an individual,
248-422: A revised taxonomy based on a concept strongly resembling clades, although the term clade itself would not be coined until 1957 by his grandson, Julian Huxley . German biologist Emil Hans Willi Hennig (1913–1976) is considered to be the founder of cladistics . He proposed a classification system that represented repeated branchings of the family tree, as opposed to the previous systems, which put organisms on
279-641: A single species, Xiaotingia zhengi . Xiaotingia is known from the holotype STM 27-2, an articulated and almost complete skeleton including the skull . It was probably collected in the Linglongta area, Jianchang , from the Tiaojishan Formation . Xiaotingia was first named by Xu Xing , You Hailu , Du Kai and Han Fenglu in 2011 and the type species is Xiaotingia zhengi . The generic name and specific name together honour paleontologist Zheng Xiaoting . Xiaotingia
310-429: A suffix added should be e.g. "dracohortian". A clade is by definition monophyletic , meaning that it contains one ancestor which can be an organism, a population, or a species and all its descendants. The ancestor can be known or unknown; any and all members of a clade can be extant or extinct. The science that tries to reconstruct phylogenetic trees and thus discover clades is called phylogenetics or cladistics ,
341-476: Is in turn included in the mammal, vertebrate and animal clades. The idea of a clade did not exist in pre- Darwinian Linnaean taxonomy , which was based by necessity only on internal or external morphological similarities between organisms. Many of the better known animal groups in Linnaeus's original Systema Naturae (mostly vertebrate groups) do represent clades. The phenomenon of convergent evolution
SECTION 10
#1732791827543372-515: Is responsible for many cases of misleading similarities in the morphology of groups that evolved from different lineages. With the increasing realization in the first half of the 19th century that species had changed and split through the ages, classification increasingly came to be seen as branches on the evolutionary tree of life . The publication of Darwin's theory of evolution in 1859 gave this view increasing weight. In 1876 Thomas Henry Huxley , an early advocate of evolutionary theory, proposed
403-489: Is still controversial. As an example, see the full current classification of Anas platyrhynchos (the mallard duck) with 40 clades from Eukaryota down by following this Wikispecies link and clicking on "Expand". The name of a clade is conventionally a plural, where the singular refers to each member individually. A unique exception is the reptile clade Dracohors , which was made by haplology from Latin "draco" and "cohors", i.e. "the dragon cohort "; its form with
434-461: The Yixian and Jifuotang Formations of Liaoning County of China, and the putative Late Cretaceous member Hesperonychus from North America is subsequently classified as an eudromaeosaurian , an avialan , or a sister taxon (not a member) of microraptorians by other researchers. They are sometimes referred to as "Liaoning dromaeosaursids", even though it is uncertain whether Zhenyuanlong from
465-443: 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 possibly were able to use these wings to glide or take off from
496-520: The clade Aves currently in use, pointing out that their definitions are compatible with a traditional Aves with Archaeopteryx as a specifier. This phylogenetic hypothesis was challenged by an analysis using different methods published several months later however, in which Archaeopteryx was again recovered as an avialan, while Xiaotingia remained closely allied to Anchiornis within the Troodontidae. In 2012, an expanded and revised version of
527-466: The dromaeosaurid family. 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 the Dromaeosauridae proper. Sereno offered a revised definition of the subgroup containing Microraptor to ensure that it would fall within the Dromaeosauridae, and erected
558-476: The exclusion of other groups traditionally seen as birds. Xu et al. therefore (re)defined the concepts of Deinonychosauria and Avialae to the extent that Archaeopteryx and Xiaotingia belonged to the Deinonychosauria in the clade Archaeopterygidae . This led to popular reports that " Archaeopteryx is no longer a bird", although Xu et al. noted that there are several competing definitions of
589-472: The femur were quite long, measuring 55 mm. It also had long pennaceous feathers on its tibia and metatarsus. If Xiaotingia could fly short distances it might also have used its hind limbs as wings. Xiaotingia had a dentary tooth count probably less than 10 and teeth similar in morphology to those of basal avians. The initial analysis by Xu et al. showed that Xiaotingia formed a clade with Archaeopteryx , Dromaeosauridae and Troodontidae to
620-409: The ground, and perhaps even capable of powered flight. Microraptorines can be distinguished from other dromaeosaurids by these 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 Dromaeosauridae , though some consider the group to be outside
651-423: 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 kg (2.2 lb), making them some of the smallest known non-avialan dinosaurs . Microraptorians were a group of basal dromaeosaurids (popularly known as "raptors") with slender proportions and long limbs. All definitive members have been found in
SECTION 20
#1732791827543682-640: The initial analysis also found Archaeopteryx to be avialan and Anchiornis to be troodontid, but recovered Xiaotingia as the most primitive member of the clade Dromaeosauridae rather than a close relative of Anchiornis within Troodontidae. Cladogram following the results of a phylogenetic study by Lefèvre et al. , 2017. † Oviraptorosauria † Scansoriopterygidae † Xiaotingia † Yixianosaurus † Pedopenna † Aurornis † Serikornis † Eosinopteryx † Anchiornis † Troodontidae † Dromaeosauridae † Archaeopteryx † Rahonavis † Balaur † Jeholornithidae Euavialae In
713-518: The latter term coined by Ernst Mayr (1965), derived from "clade". The results of phylogenetic/cladistic analyses are tree-shaped diagrams called cladograms ; they, and all their branches, are phylogenetic hypotheses. Three methods of defining clades are featured in phylogenetic nomenclature : node-, stem-, and apomorphy-based (see Phylogenetic nomenclature§Phylogenetic definitions of clade names for detailed definitions). The relationship between clades can be described in several ways: The age of
744-482: The relationships between organisms that the molecular biology arm of cladistics has revealed include that fungi are closer relatives to animals than they are to plants, archaea are now considered different from bacteria , and multicellular organisms may have evolved from archaea. The term "clade" is also used with a similar meaning in other fields besides biology, such as historical linguistics ; see Cladistics § In disciplines other than biology . The term "clade"
775-596: The same locality is a microraptorian. These formations (collectively known as the Jehol Biota ) 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. Most microraptorians were small dinosaurs, with taxa such as Microraptor and especially Zhongjianosaurus being among
806-508: 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 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
837-449: 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,
868-555: The spread of viral infections . HIV , for example, has clades called subtypes, which vary in geographical prevalence. HIV subtype (clade) B, for example is predominant in Europe, the Americas and Japan, whereas subtype A is more common in east Africa. Xiaotingia Xiaotingia is a genus of anchiornithid theropod dinosaur from Middle Jurassic or early Late Jurassic deposits of western Liaoning , China , containing
899-611: 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. Xiaotingia Unenlagiinae Shanag Saurornitholestinae Velociraptorinae Dromaeosaurinae Tianyuraptor Hesperonychus Microraptor sp. Microraptor gui Microraptor zhaoianus Cryptovolans Graciliraptor Sinornithosaurus In
930-423: Was coined in 1957 by the biologist Julian Huxley to refer to the result of cladogenesis , the evolutionary splitting of a parent species into two distinct species, a concept Huxley borrowed from Bernhard Rensch . Many commonly named groups – rodents and insects , for example – are clades because, in each case, the group consists of a common ancestor with all its descendant branches. Rodents, for example, are
961-506: Was morphologically similar to other anchiornithids . It was about 60 cm long and weighed an estimated 0.82 kg. It was a small feathered dinosaur that lived in an arboreal environment. Like Archaeopteryx it had long forelimbs. Its femur was longer than its humerus, 84 mm compared to 71 mm, which might indicate that it stood on its hind limbs and could flap its forelimbs to achieve flight. Xiaotingia had feathers on its head, body, forelimbs and hind limbs. The feathers on