52-469: Unenlagiidae is a proposed family of eumaniraptoran paravians that includes the subfamilies Unenlagiinae and possibly Halszkaraptorinae . Fossils of both subfamilies have been found in both Gondwanan and Laurasian deposits. The biology of the group suggests that some members were semiaquatic specialists. The family Unenlagiidae traditionally includes the same members as the previously named subfamily of Dromaeosauridae , Unenlagiinae , so Unenlagiidae
104-416: A natural group . The name 'Paraves' (Greek pará , par' 'beside, near' + Latin aves , plural of avis 'bird') was coined by Sereno in 1997. The clade was defined by Sereno in 1998 as a branch-based clade containing all Maniraptora closer to Neornithes (which includes all the birds living in the world today) than to Oviraptor . A node-based clade called Eumaniraptora ("true maniraptorans")
156-490: A bird-like arrangement of the pectoral bones, where the angled shoulder girdle (coracoids) come in contact with the breastbone (sternum). According to Paul, ornithomimosaurs are the most basal members of this group. In 2010, Paul used Avepectora for a smaller clade, excluding ornithomimosaurs, compsognathids and alvarezsauroids. Within Coelurosauria exists a slightly less inclusive clade named Tyrannoraptora . This clade
208-541: A clade (all theropods closer to dromaeosaurids than to birds) by Jacques Gauthier in 1986. However, several more recent studies have cast doubt on the hypothesis that dromaeosaurids and troodontids were more closely related to each other than either was to birds, instead finding that troodontids were more closely related to birds than to dromaeosaurids. Because Deinonychosauria was originally defined as all animals closer to dromaeosaurids than to birds without specific reference to troodontids, this would render Deinonychosauria
260-481: A clade including Troodontidae and Avialae . In 2015 Chatterjee created Tetrapterygidae in the second edition of his book The Rise of Birds: 225 Million Years of Evolution , where he included Microraptor , Xiaotingia , Aurornis , and Anchiornis ; together they were proposed to be the sister group of the Avialae . Paraves , Eumaniraptora , and Averaptora are often considered to be synonyms, depending on
312-467: A common origin with avemetatarsalians . Although rare, complete casts of theropod endocrania are known from fossils. Theropod endocrania can also be reconstructed from preserved braincases without damaging valuable specimens by using a computed tomography scan and 3D reconstruction software. These finds are of evolutionary significance because they help document the emergence of the neurology of modern birds from that of earlier reptiles. An increase in
364-424: A second set of airfoils. These species, most famously represented by Microraptor gui , have often been referred to as "four winged dinosaurs". Though it has been suggested that these hind wings would have prevented some paravians from getting around on the ground, and that they must have lived in trees, there is very little evidence that any of the earliest paravians were capable of climbing. This apparent paradox
416-534: A study by paleontologist Thomas Holtz found a close relationship between the Ornithomimosauria and Troodontidae , and named this group Bullatosauria . Holtz rejected this hypothesis in 1999, and most paleontologists now consider troodontids to be much more closely related to either birds or Dromaeosauridae than they are to ornithomimosaurs, causing the Bullatosauria to be abandoned. The name referred to
468-618: A synonym of Dromaeosauridae. The clade containing avialans, microraptorians, unenlagiids, Anchiornis , and Xiaotingia to the exclusion of Eudromaeosauria was named Averaptora by Agnolín and Novas (2013), defined as all animals closer to Passer than to Dromaeosaurus . Most studies use a similar definition for Avialae , which Agnolín and Novas redefine as the least inclusive clade including Archaeopteryx and modern birds. Averaptora additionally contains troodontids according to Cau, Beyrand, Voeten et al . (2017) and other phylogenies in which find Eudromaeosauria to be an outgroup to
520-499: Is Neocoelurosauria , erected by Hendrickx, Mateus, Araújo and Choiniere (2019), They define it as "the clade Compsognathidae + Maniraptoriformes", which can be more or less inclusive than Maniraptoromorpha depending on the topology. The last, and most exclusive of these proposed subclades is Maniraptoriformes . Maniraptoriformes is a clade which may have been united by the presence of pennaceous feathers and wings. This clade contains ornithomimosaurs and maniraptorans . The group
572-463: Is a branch-based clade defined to include all dinosaurs which are more closely related to birds than to oviraptorosaurs . The ancestral paravian is the earliest common ancestor of birds, dromaeosaurids , and troodontids which was not also ancestral to oviraptorosaurs . Paraves often comprises three major sub-groups: Avialae , including Archaeopteryx and modern birds, as well as the dromaeosaurids and troodontids , which may or may not form
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#1732880701221624-531: Is a stub . You can help Misplaced Pages by expanding it . Paraves 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 avialans , which include diverse extinct taxa as well as the over 10,000 species of living birds . Basal members of Paraves are well known for
676-659: Is the clade containing all theropod dinosaurs more closely related to birds than to carnosaurs . Coelurosauria is a subgroup of theropod dinosaurs that includes compsognathids , tyrannosaurs , ornithomimosaurs , and maniraptorans ; Maniraptora includes birds , the only known dinosaur group alive today. Most feathered dinosaurs discovered so far have been coelurosaurs. Philip J. Currie had considered it likely and probable that all coelurosaurs were feathered. However, several skin impressions found for some members of this group show pebbly, scaly skin, indicating that feathers did not completely replace scales in all taxa. In
728-429: Is unknown whether these are related to true feathers, recent analysis has suggested that the feather-like integument found in ornithischians may have evolved independently of coelurosaurs but this was estimated by assuming that primitive pterosaurs had scales. In 2018, two anurognathid specimens were found to have integumentary structures similar to protofeathers. Based on phylogenetic analysis, protofeathers would have had
780-699: The Morrison Formation in Wyoming at about 150 Ma. Epidendrosaurus and Pedopenna are known from the Daohugou Beds in China at about 165-163 Ma. The wide range of fossils in the late Jurassic and morphological evidence shows that coelurosaurian differentiation was virtually complete before the end of the Jurassic. In the early Cretaceous , a superb range of coelurosaurian fossils (including avians) are known from
832-701: The Yixian Formation in Liaoning. All known theropod dinosaurs from the Yixian Formation are coelurosaurs. Many of the coelurosaurian lineages survived to the end of the Cretaceous period (about 66 Ma) and fossils of some lineages, such as the Tyrannosauroidea , are best known from the late Cretaceous. A majority of coelurosaur groups became extinct in the Cretaceous–Paleogene extinction event , including
884-458: The proceratosaurid tyrannosauroids Proceratosaurus and Kileskus from the late Middle Jurassic. Many nearly complete fossil coelurosaurians are known from the Late Jurassic . Archaeopteryx (incl. Wellnhoferia ) is known from Bavaria at 155-150 Ma. Ornitholestes , the troodontid Hesperornithoides , Coelurus fragilis and Tanycolagreus topwilsoni are all known from
936-469: The tyrannosaurids , were actually more advanced than allosaurs and therefore were reclassified as giant coelurosaurs. Even more drastically, the segnosaurs , once not even regarded as theropods, have turned out to be non-carnivorous coelurosaurs related to Therizinosaurus . Senter (2007) listed 59 different published phylogenies since 1984. Those since 2005 have followed almost the same pattern, and differ significantly from many older phylogenies. In 1994,
988-505: The 1960s several distinctive lineages of coelurosaurs were recognized, and a number of new infraorders were erected, including the Ornithomimosauria , Deinonychosauria , and Oviraptorosauria . During the 1980s and 1990s, paleontologists began to give Coelurosauria a formal definition, usually as all animals closer to birds than to Allosaurus , or equivalent specifiers. Under this modern definition, many small theropods are not classified as coelurosaurs at all and some large theropods, such as
1040-555: The Tyrannosauroidea, Ornithomimosauria , Oviraptorosauria , Deinonychosauria , Enantiornithes , and Hesperornithes . Only the Neornithes , otherwise known as modern birds, survived, and continued to diversify after the extinction of the other dinosaurs into the numerous forms found today. There is consensus among paleontologists that birds are descended from coelurosaurs. Under modern cladistical definitions, birds are considered
1092-431: The best-known features of paravians is the presence of an enlarged and strongly curved "sickle claw" on a hyper-extendible second toe, modified to hold the sickle claw clear of the ground when walking, most notably developed in the dromaeosaurids and troodontids. While this characteristic claw and its associated modifications to the anatomy of the foot (such as a shortened metatarsus in eudromaeosaurs ) had been known since
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#17328807012211144-681: The body mass continued to decrease in many forms within Avialae . Fossils show that all the earliest members of Paraves found to date started out as small, while Troodontidae and Dromaeosauridae gradually increased in size during the Cretaceous period. † Oviraptorosauria † Scansoriopterygidae † Xiaotingia † Yixianosaurus † Pedopenna † Aurornis † Serikornis † Eosinopteryx † Anchiornis † Troodontidae † Dromaeosauridae Avialae † Oviraptorosauria † Dromaeosauridae † Troodontidae † Anchiornithinae † Archaeopteryx † Scansoriopterygidae † Rahonavis Pygostylia Paraves
1196-418: The claws highly reduced or lost in some advanced lineages. An increasingly asymmetric wrist joint, a trend that can be traced back to primitive coelurosaurs , allowed the forelimbs to elongate and an elaboration of their plumage, traits that made the evolution of flapping flight possible. Many early members of Paraves had both well-developed wings and long feathers on the hind legs, which in some cases, formed
1248-474: The earlier study by Manning and colleagues was correct and that the "sickle claws" would have been ineffective as cutting weapons. They compared the claw and overall foot anatomy of various primitive species with modern birds to shed light on their actual function. Fowler and colleagues showed that many modern predatory birds also have enlarged claws on the second toes. In modern raptors, these claws are used to help grip and hold prey of sizes smaller than or equal to
1300-653: The early Jurassic 200 million years ago, and fossil evidence shows that this theropod line evolved new adaptations four times faster than other groups of dinosaurs, and was shrinking 160 times faster than other dinosaur lineages were growing. Turner et al . (2007) suggested that extreme miniaturization was ancestral for the clade, whose common ancestor has been estimated to have been around 65 centimetres (26 in) long and 600–700 grams (21–25 oz) in mass. In Eumaniraptora , both Dromaeosauridae and Troodontidae went later through four independent events of gigantism, three times in dromaeosaurids and once in troodontids, while
1352-553: The feet were not as specialized and the claws were not as large or as hooked. Additionally, the toe joints allowed more range of motion than the simple up-down movements of advanced dromaeosaurids. This makes it likely that these species specialized in smaller prey that could be pinned using only the inner toes, not requiring the feet to be as strong or sturdy. Extreme examples of miniaturization and progenesis are found in Paraves. The ancestors of Paraves first started to shrink in size in
1404-572: The feet, though some primitive coelurosaurian species are known to have had scales on the upper legs and portions of the tail as well. These include tyrannosauroids , Juravenator , and Scansoriopteryx . Fossils of at least some of these animals ( Scansoriopteryx and possibly Juravenator ) also preserve feathers elsewhere on the body. Though once thought to be a feature exclusive to coelurosaurs, feathers or feather-like structures are also known in some ornithischian dinosaurs (like Tianyulong and Kulindadromeus ), and in pterosaurs . Though it
1456-410: The first toe ( hallux ) was usually small and angled inward toward the center of the body, but only became fully reversed in more specialized members of the bird lineage. One species, Balaur bondoc , possessed a first toe which was highly modified in parallel with the second. Both the first and second toes on each foot of B. bondoc were held retracted and bore enlarged, sickle-shaped claws. One of
1508-536: The front edge of dromaeosaurid and troodontid teeth were very small and fine, while the back edge had serrations which were very large and hooked. Most of the earliest paravian groups were carnivorous, though some smaller species (especially among the troodontids and early avialans) are known to have been omnivores, and it has been suggested that an omnivorous diet was the ancestral state for this group, with strict carnivory evolving in some specialized lineages. Fossils also suggest that legs and feet covered with feathers
1560-409: The ground, while using shallow wing beats and tail movements to stabilize themselves. Other lines of evidence for this behavior include teeth which had large, hooked serrations only on the back edge (useful in pulling flesh upward rather than slicing it) and large claws on the wings (for greater maneuvering of prey while mantling it with the wings). In more primitive dromaeosaurids and in troodontids,
1612-426: The inflated (bulbous) sphenoid both groups shared. Holtz defined the group as the clade containing the most recent common ancestor of Troodon and Ornithomimus and all its descendants. The concept is now considered redundant, and the clade Bullatosauria is now viewed as synonymous with Maniraptoriformes. In 2002, Gregory S. Paul named an apomorphy-based clade Avepectora , defined to include all theropods with
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1664-429: The interpretation of paravian systematics. Deinonychosauria will become a synonym of Dromaeosauridae when troodontids are found to form a clade with Avialae, to the exclusion of Dromaeosauridae. Tetrapterygidae is a polyphyletic grouping of four-winged basal paravian genera. Paravians diverged from other maniraptorans around 165 Mya . Then, around 110–90 Mya, the ancestors of Neornithes (modern birds) split from
1716-490: The largest ( Tyrannosaurus ) and smallest ( Microraptor , Parvicursor ) carnivorous dinosaurs ever discovered. Characteristics that distinguish coelurosaurs include: Fossil evidence shows that the skin of even the most primitive coelurosaurs was covered primarily in feathers . Fossil traces of feathers, though rare, have been found in members of most major coelurosaurian lineages. Most coelurosaurs also retained scales and scutes on some portion of their bodies, particularly
1768-406: The mid-20th century, their possible functions were the subject mainly of speculation, and few actual studies were published. Initial speculation regarded the claws as slashing implements used to disembowel large prey. In this scenario, the shortened upper foot would serve as an anchor point for powerful tendons to improve kicking ability. However, subsequent studies of the actual claw shape showed that
1820-427: The only exceptions being particularly basal species such as Zuolong salleei or Sciurumimus albersdoerferi . Several recently-named clades have been proposed to define the structure of Coelurosauria crownward of basal groups such as tyrannosauroids and compsognathids. Maniraptoromorpha , defined by Andrea Cau in 2018, includes all coelurosaurians more closely related to birds than to tyrannosauroids. Cau stated that
1872-472: The only known non-eumaniraptoran paravian. Since the 1960s, the dromaeosaurids and troodontids have often been classified together in a group or clade named the Deinonychosauria , initially based primarily on the presence of a retractable second toe with sickle-claw (now also known to be present in some avialans). The name Deinonychosauria was coined by Ned Colbert and Dale Russell in 1969, and defined as
1924-419: The only living lineage of coelurosaurs. Birds are classified by most paleontologists as belonging to the subgroup Maniraptora . A portion of a tail belonging to a juvenile coelurosaur was found in 2015, inside of a piece of amber. The phylogeny and taxonomy of Coelurosauria has been subject to intensive research and revision. For many years, Coelurosauria was a 'dumping ground' for all small theropods. In
1976-552: The other paravians. Other than the crown group of modern birds, which are direct descendants in the stem lineage of Paraves, there are no extant survivors or genetic material, so their entire phylogeny is inferred only from the fossil record. The prototypical fossil is Archaeopteryx , of which 11 specimens have been found , both complete and partial. [REDACTED] [REDACTED] Coelurosauria Coelurosauria ( / s ɪ ˌ lj ʊər ə ˈ s ɔːr i . ə / ; from Greek , meaning "hollow-tailed lizards")
2028-620: The past, Coelurosauria was used to refer to all small theropods, but this classification has since been amended. The studying of anatomical traits in coelurosaurs indicates that the last common ancestor had evolved the ability to eat and digest plant matter, adapting to an omnivorous diet, an ability that could be a major contributor to the clade's success. Later groups would hold on to the omnivory, while others specialized in various directions, becoming insectivorous ( Alvarezsauridae ), herbivorous ( Therizinosauridae ) and carnivorous ( Tyrannosauroidea and Dromaeosauridae ). The group includes some of
2080-583: The possession of an enlarged claw on the second digit of the foot, which was held off the ground when walking in some species. A number of differing scientific interpretations of the relationships between paravian taxa exist. New fossil discoveries and analyses make the classification of Paraves an active subject of research. Like other theropods, all paravians are bipedal, walking on their two hind legs. The teeth of basal paravians were curved and serrated, but not blade-like except in some specialized species, such as Dromaeosaurus albertensis . The serrations on
2132-450: The predator, while the birds use their body weight to pin their prey to the ground and eat it alive. Fowler and colleagues suggested that this behavior is entirely consistent with the anatomy of advanced dromaeosaurids like Deinonychus , which had slightly opposing first toes and strong tendons in the toes and foot. This makes it likely that advanced dromaeosaurids also used their claws to puncture and grip their prey to aid in pinning it to
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2184-439: The proportion of the brain occupied by the cerebrum seems to have occurred with the advent of the Coelurosauria and "continued throughout the evolution of maniraptorans and early birds." A few fossil traces tentatively associated with the Coelurosauria date as far back as the late Triassic . What has been found between then and the earliest Middle Jurassic is fragmentary. The oldest known unambiguous members of Coelurosauria are
2236-428: The second toe off the ground in a hyperextended position, with only the third and fourth toes bearing the weight of the animal. This is called functional didactyly. The enlarged second toe bore an unusually large, curved sickle-shaped claw (held off the ground or 'retracted' when walking). This claw was especially large and flattened from side to side in the large-bodied predatory eudromaeosaurs . In these early species,
2288-430: The synapomorphies of the clade included "Keel or carinae in the postaxial cervical centra, absence of hyposphene-hypantra in caudal vertebrae (reversal to the plesiomorphic theropodan condition), a prominent dorsomedial process on the semilunate carpal, a convex ventral margin of the pubic foot, a subrectangular distal end of tibia and a sulcus along the posterior margin of the proximal end of fibula." Another proposed clade
2340-787: The traditional placement of Halszkaraptorinae and Unenlagiinae in Dromaeosauridae, forming no distinct clade. In 2021, Brum et al. named the clade Unenlagiinia for a unified Unenlagia + Halszkaraptor clade, recovering them as basal dromaeosaurs. The following cladogram is from Motta et al. , 2020, showing Unenlagiidae outside dromaeosaurids and more closely related to Avialae: Troodontidae Dromaeosauridae Microraptoria Austroraptor Buitreraptor Unenlagia Overoraptor Rahonavis Alcmonavis Wellnhoferia Archaeopteryx Xiaotingia Anchiornis Jeholornis Pygostylia [REDACTED] [REDACTED] This theropod -related article
2392-459: The underside of the claw was only weakly keeled and would not have been an effective cutting instrument. Instead, it appeared to be more of a hooking implement. Manning et al. suggested in 2006 that the claws were similar to crampons and were used for climbing, and in the case of larger species or individuals, climbing up the flanks of very large prey. A larger study of sickle-claw function, published in 2011 by Fowler and colleagues, concluded that
2444-523: Was addressed by later studies which showed that early paravians like Microraptor were capable of flapping flight and powered launching from the ground into the air without relying on climbing. Microraptor in particular also seems to represent a case of flight evolving independently of the bird lineage within Paraves. Most theropods walked with three toes contacting the ground, but fossilized footprint tracks confirm that many basal paravians, including dromaeosaurids, troodontids, and some early avialans, held
2496-478: Was an ancestral condition, possibly having originated in the Coelurosauria , even if this trait was later lost in more advanced birds. Paravians generally have long, winged forelimbs, though these have become smaller in many flightless species and some extinct lineages that evolved before flight. The wings usually bore three large, flexible, clawed fingers in early forms. The fingers became fused and stiffened and
2548-423: Was defined by Sereno (1999) as " Tyrannosaurus rex , Passer domesticus (the house sparrow), their last common ancestor , and all of its descendants". As tyrannosauroids are considered to be the most basal large group within Coelurosauria, this means that the common ancestor of tyrannosauroids and birds was an even more basal coelurosaurian. As a result, almost all coelurosaurians are also tyrannoraptorans, with
2600-460: Was named by Thomas Holtz , who defined it as "the most recent common ancestor of Ornithomimus and birds , and all descendants of that common ancestor." One of the possible synapomorphies of this clade is the presence of feathers homologous to those of birds, based on study of a specimen of Shuvuuia . The following family tree illustrates a synthesis of the relationships of the major coelurosaurian groups based on various studies conducted in
2652-491: Was named by Padian, Hutchinson, & Holtz (1997). They defined their clade to include only avialans and deinonychosaurs. Paraves and Eumaniraptora are generally considered to be synonyms, though some phylogenetic studies suggest that the two groups have a similar but not identical content; Agnolín and Novas (2011) recovered scansoriopterygids and alvarezsaurids as paravians that were not eumaniraptorans, while Turner, Makovicky, and Norell (2012) recovered Epidexipteryx as
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#17328807012212704-487: Was often seen as a synonym of Dromaeosauridae. However, since the 2010s, there have been subsequent studies that have questioned this placement, necessitating the revival of the family name. Some have placed unenlagiids as outside Dromaeosauridae, being the sister taxon or closely related to Avialae , while others have placed the newly recognized halszkaraptorines in the family, as basal deinonychosaurs outside Dromaeosauridae and Troodontidae . Other recent studies supported
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