44-531: Oviraptorosaurs ("egg thief lizards") are a group of feathered maniraptoran dinosaurs from the Cretaceous Period of what are now Asia and North America . They are distinct for their characteristically short, beaked, parrot-like skulls, with or without bony crests atop the head. They ranged in size from Caudipteryx , which was the size of a turkey, to the 8-meter-long, 1.4-ton Gigantoraptor . The group (along with all maniraptoran dinosaurs)
88-490: A clade (natural grouping) of maniraptorans more primitive than true birds. They found that the oviraptorosaurs are the sister group to the Therizinosauria and that the two, together, are more basal than any member of Paraves . However, a more recent study by Zanno and colleagues challenged that finding, showing therizinosaurs to be more primitive and not closely related to oviraptorosaurs. The following cladogram
132-608: A dromaeosaurid , was too heavy to fly but still had wings with feathers required for flying, which suggests its ancestors had the ability for aerial locomotion. Other groups, like the Oviraptorosauria who had a tail with a tail fan of feathers with caudal anatomy resembling a pygostyle , are not known to have been capable of flight, but some scientists, such as Gregory S. Paul , have suggested that they could be descended from ancestors which flew. Paul has gone as far as to propose that Therizinosauria , Alvarezsauroidea , and
176-493: A 2001 paper. Their proposed definition for the group was "the clade stemming from the first panavian with ... remiges and rectrices , that is, enlarged, stiff-shafted, closed-vaned (= barbules bearing hooked distal pennulae), pennaceous feathers arising from the distal forelimbs and tail". Ancestral morphology relating to pennaceous feathers suggests that basal species of Pennaraptora were capable of scansorial locomotion and gliding, and further evolution of said adaptation within
220-500: A feathered bird-like predator) is a clade within Maniraptora, defined as the most recent common ancestor of Oviraptor philoceratops , Deinonychus antirrhopus , and Passer domesticus (the house sparrow), and all descendants thereof, by Foth et al. , 2014. The clade "Aviremigia" was conditionally proposed along with several other apomorphy -based clades relating to birds by Jacques Gauthier and Kevin de Queiroz in
264-503: A long, backwards-pointed pubis and short ischia were present in Scansoriopteryx , a scansoriopterygid. The authors considered it to be more primitive than true theropods, and hypothesized that maniraptorans may have branched off from theropods at a very early point, or may even have descended from pre-theropod dinosaurs. Zhang et al. , in describing the closely related or conspecific specimen Epidendrosaurus (now considered
308-450: A number of discoveries made during the first decade of the 21st century, as well as re-evaluation of older evidence, began to suggest that maniraptorans were a primarily omnivorous group, including a number of sub-groups that ate mainly plants, insects, or other food sources besides meat. Additionally, phylogenetic studies of maniraptoran relationships began to more consistently show that herbivorous or omnivorous groups were spread throughout
352-441: A pygostyle, a bony structure at the end of the tail that, in modern birds, is used to support a fan of feathers. Similarly, quill knobs (anchor points for wing feathers on the ulna) have been reported in the oviraptorosaur species Avimimus portentosus . Additionally, a number of oviraptorid specimens have famously been discovered in a nesting position similar to that of modern birds. The arms of these specimens are positioned in such
396-482: A synonym of Scansoriopteryx ), did not report any of the primitive traits mentioned by Czerkas and Yuan, but did find that the shoulder blade of Epidendrosaurus appeared primitive. Despite this, they placed Epidendrosaurus firmly within Maniraptora due to a number of synapomorphies. Scientists traditionally assumed that maniraptorans were ancestrally hypercarnivorous , that is, that most non-avialan species primarily ate and hunted only other vertebrates . However,
440-409: A technical paper detailing this idea in 2002. Michael Benton , in his widely respected text Vertebrate Paleontology , wrote placement of oviraptorosaurs among birds is highly controversial . However, a number of researchers have disagreed with this classification, retaining oviraptorosaurs as non-avialan maniraptorans slightly more primitive than the deinonychosaurs . The internal classification of
484-521: A very strong bite force. The moderate jaw gape seen in oviraptorosaurs is indicative of herbivory in the majority of the group, but it is clear they were likely feeding on much tougher or more types of vegetation than other herbivorous theropods in their environment, such as ornithomimosaurs and therizinosaurs were able to. The examinations suggest oviraptorosaurs may have been powerful-biting generalists or specialists that partook of niche partitioning both in body size and cranial function. One particular group,
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#1732783230020528-472: A way that they could perfectly cover their eggs if they had small wings and a substantial covering of feathers. Notably, a study on flight feathers has concluded that Caudipteryx was secondarily flightless, implying an ancestral volant ancestor for oviraptorosaurs. The eating habits of these animals are not fully known: they have been suggested to have been either carnivorous , herbivorous , mollusk-eating or egg-eating (the evidence that originally supported
572-472: Is a clade of coelurosaurian dinosaurs which includes the birds and the non-avian dinosaurs that were more closely related to them than to Ornithomimus velox . It contains the major subgroups Avialae , Dromaeosauridae , Troodontidae , Oviraptorosauria , and Therizinosauria . Ornitholestes and the Alvarezsauroidea are also often included. Together with the next closest sister group,
616-528: Is close to the ancestry of birds . Some researchers such as Maryanska et al (2002) and Osmólska et al. (2004) have proposed that they may represent primitive flightless birds. The most complete oviraptorosaur specimens have been found in Asia. The North American oviraptorosaur record is sparse. The earliest and most basal ("primitive") known oviraptorosaurs are Ningyuansaurus wangi , Protarchaeopteryx robusta and Incisivosaurus gauthieri , both from
660-419: Is vertical or subvertical, with a concave anterior edge. The tibia is 15%-25% longer than the femur. The tail is short, with the number of vertebrae reduced to 24 or so, and proximally very thick, with broad transverse processes . The ischium retains the primitive character of a prominent, triangular obturator process and lack the proximodorsal process that is found in birds. In advanced oviraptorosaurs,
704-502: The Caenagnathidae , may have also been more omnivorous or even carnivorous than other oviraptorosaurs. Several oviraptorosaur nests are known, with several oviraptorid specimens preserved in a brooding position over large clutches of up to a dozen or more eggs. The eggs are usually arranged in pairs, and forming a circular pattern within the nest. One oviraptorosaur specimen from China has been found with two unlaid eggs within
748-533: The Ornithomimosauria , Maniraptora comprises the more inclusive clade Maniraptoriformes . Maniraptorans first appear in the fossil record during the Jurassic Period (see Eshanosaurus ), and survive today as living birds. Maniraptorans are characterized by long arms and three-fingered hands (though reduced or fused in some lineages), as well as a "half-moon shaped" (semi- lunate ) bone in
792-520: The scansoriopterygids , Pedopenna , and Yixianosaurus . In 1993, Perle and colleagues coined the name Metornithes to include alvarezsaurids and modern birds, which the researchers believed were members of the Avialae. This group was defined as a clade by Luis Chiappe in 1995 as the last common ancestor of Mononykus and modern birds, and all its descendants. Pennaraptora (Latin penna "bird feather" + raptor "thief", from rapere "snatch";
836-491: The ulna , greater trochanter and cranial trochanter of the femur fused into a trochanteric crest . An elongated, backwards-pointing pubic bone is present in therizinosauroids, dromaeosaurids, avialans, and the basal troodontid Sinovenator , which suggests that the propubic condition in advanced troodontids and oviraptorosaurs is a reversal. Turner et al. (2007) named seven synapomorphies that diagnose Maniraptora. Modern pennaceous feathers and remiges are known in
880-461: The Maniraptora, rather than representing a single side-branch as previously thought. This led scientists such as Lindsay Zanno to conclude that the ancestral maniraptoran must have been omnivorous, giving rise to several purely herbivorous groups (such as the therizinosaurs, primitive oviraptorosaurs, and some avialans) and that, among non-avians, only one group reverted to pure carnivores (the dromaeosaurids). Most other groups fell somewhere in between
924-418: The advanced maniraptoran group Aviremigia . More primitive maniraptorans, such as therizinosaurs (specifically Beipiaosaurus ), preserve a combination of simple downy filaments and unique elongated quills. Simple feathers are known from more primitive coelurosaurs such as Sinosauropteryx prima , and possibly from even more distantly related species such as the ornithischian Tianyulong confuciusi and
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#1732783230020968-444: The backward-pointing hip is present in so many diverse maniraptoran groups has led most scientists to conclude that the "primitive" forward-pointing hip seen in advanced troodontids and oviraptorosaurs is an evolutionary reversal, and that these groups evolved from ancestors with backward-pointing hips. Holtz and Osmólska (2004) diagnosed the clade Maniraptora based on the following characters: reduced or absent olecranon process of
1012-593: The birth canal shows that oviraptorosaurs were intermediate between the reproductive biology of crocodilians and modern birds. Like crocodilians, they had two oviducts . However, crocodilians produce multiple shelled eggs per oviduct at a time, whereas oviraptorosaurs, like birds, produced only one egg per oviduct at a time. Oviraptorosaurs, like deinonychosaurs , are so bird-like that several scientists consider them to be true birds, more advanced than Archaeopteryx . Gregory S. Paul has written extensively on this possibility, and Teresa Maryańska and colleagues published
1056-479: The clade would eventually give rise to the origin of flight in avian species. The following cladogram follows the results of a phylogenetic study by Cau (2020). † Alvarezsauroidea [REDACTED] † Therizinosauridae [REDACTED] † Oviraptorosauria [REDACTED] † Dromaeosauridae [REDACTED] † Troodontidae [REDACTED] Avialae [REDACTED] In 2002, Czerkas and Yuan reported that some maniraptoran traits, such as
1100-541: The crested oviraptorids. Studies today accept two major subclades outside of the Caenagnathidae and Oviraptoridae: Caenagnathoidea, which strictly includes the two major families, and Edentoraptora, which also incorporates Avimimus , so called because of the edentulous dentition of Avimimus and the caenagnathoids. The 2007 cladistic analysis of Turner and colleagues recovered the Oviraptorosauria as
1144-439: The earlier branch-based definition. The branch-based definition usually includes the major groups Dromaeosauridae , Troodontidae , Oviraptorosauria , Therizinosauria , and Avialae . Other taxa often found to be maniraptorans include the alvarezsaurs and Ornitholestes . Several taxa have been assigned to the Maniraptora more definitively, though their exact placement within the group remains uncertain. These forms include
1188-528: The exception of the 8-meter long Gigantoraptor , they are generally medium-sized and rarely exceeded 2 meters in length. The most primitive members have four pairs of teeth in the premaxillae , such as in Caudipteryx and in Incisivosaurus they are enlarged and form bizarrely prominent bucktoothed incisors. The more advanced members have no teeth in the jaws. Pneumatization is extensive in
1232-513: The flying pterosaurs . Thus it appears as if some form of feathers or down-like integument would have been present in all maniraptorans, at least when they were young. Maniraptora is the only dinosaur group known to include flying members, though how far back in this lineage flight extends is controversial. Powered and/or gliding flight is believed to have been present in some types of non-avialan paravians, including dromaeosaurids, such as Rahonavis and Microraptor . Zhenyuanlong suni ,
1276-425: The form of their skulls. They have shortened snouts, beak-like jaws with few or no teeth, and a large opening in the lower jaw bone. Some have bony crests atop the skull. The most primitive members have a few teeth in the front of the mouth; in Incisivosaurus , they are enlarged and form bizarrely prominent "bucktoothed" incisors. The arms and hands are generally long (though very reduced in some advanced species) and
1320-461: The greatest egg elongation among diapsids — with the more pointed end pointing backward from the cloaca and oriented toward the center of the nest. Geochemical analysis also revealed that oviraptorosaurs incubated their eggs in the 35–40 °C (95–104 °F) range, as many modern bird species do today, based on the oxygen isotope ratios in the bones of the fossil embryos of various species during development. The presence of two shelled eggs within
1364-419: The inclusion of mollusks in their diet. Originally these animals were thought to be egg raiders, based on a Mongolian find showing Oviraptor on top of a nest. Recent studies have shown that the animal was actually on top of its own nest. A 2022 study of the bite forces of oviraptorosaurs such as Incisivosaurus , Khaan , Citipati , and Conchoraptor suggests that most if not all oviraptorosaurs had
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1408-422: The ischium is curved posteriorly. The pectoral girdle is also primitive; the scapula is a broad blade that is distally expanded, it lies on the lateral aspect of the thorax at an angle to the vertebral column, and the coracoid has the primitive coelurosaur shape with a proximal supracoracoidal nerve foramen and a moderate biceps tubercle . Oviraptorosaurs are different from most other maniraptorans in
1452-417: The latter is no longer considered valid); these options are not necessarily incompatible. Some ate small vertebrates . Evidence for this comes from a lizard skeleton preserved in the body cavity of Oviraptor and two baby Troodontid skulls found in a Citipati nest. Evidence in favor of a herbivorous diet includes the presence of gastroliths preserved with Caudipteryx . There are also arguments for
1496-588: The lower Yixian Formation of China , dating to about 125 million years ago during the Aptian age of the early Cretaceous period. A tiny neck vertebra reported from the Wadhurst Clay Formation of England shares some features in common with oviraptorosaurs, and may represent an earlier occurrence of this group (at about 140 million years ago). Oviraptorosaurs have shortened rostrums , massive, beaklike mandibles , and long parietal bones. With
1540-439: The name Maniraptora, which means "hand snatchers" in relation to their 'seizing hands'). In 1994, Thomas R. Holtz attempted to define the group based on the characteristics of the hand and wrist alone (an apomorphy-based definition), and included the long, thin fingers, bowed, wing-like forearm bones, and half-moon shaped wrist bone as key characters. Most subsequent studies have not followed this definition, however, preferring
1584-413: The non-maniraptoran group Ornithomimosauria also descended from flying ancestors. The Maniraptora was originally named by Jacques Gauthier in 1986, for a branch-based clade defined as all dinosaurs closer to modern birds than to the ornithomimids . Gauthier noted that this group could be easily characterized by their long forelimbs and hands, which he interpreted as adaptations for grasping (hence
1628-494: The oviraptorosaurs has also been controversial. Most studies divide them into two primary sub-groups, the Caenagnathidae and the Oviraptoridae . The Oviraptoridae is further divided into the small, short-armed, and crestless subfamily Ingeniinae, and the larger, crested, long-armed Oviraptorinae. However, some phylogenetic studies have suggested that many traditional members of the Caenagnathidae were more closely related to
1672-427: The pelvic canal. This suggests that, unlike modern crocodilians , oviraptorosaurs did not produce and lay many eggs at the same time. Rather, the eggs were produced within the reproductive organs in pairs, and laid two at a time, with the mother positioned in the center of the nest and rotating in a circle as each pair was laid. This behavior is supported by the fact that the eggs were shaped like highly elongated ovals —
1716-619: The pygostyle of birds (a bone which serves as the attachment point for a fan of tail feathers). Evidence for feathered oviraptorosaurs exists in several forms. Most directly, four species of primitive oviraptorosaurs (in the genera Caudipteryx , Protarchaeopteryx , and Similicaudipteryx ) have been found with impressions of well developed feathers, most notably on the wings and tail, suggesting that they functioned at least partially for display. Secondly, at least four oviraptorosaur genera ( Nomingia , Similicaudipteryx , Citipati , and Conchoraptor ) preserved tails ending in something like
1760-409: The shoulder girdle is large and massive, with flexed coracoid bones and prominent attachments for strong arm muscles. Their tails are very short compared to other maniraptorans. In Nomingia and Similicaudipteryx , the tail ends in four fused vertebrae which Osmólska, He, and others have referred to as a " pygostyle ", but which Witmer found was anatomically different and evolved separately from
1804-486: The skulls and vertebrae of the more advanced members. Oviraptorosaurs have thick, U-shaped furculae and a large sternal plates that are wider (together) than they are long, unlike in birds and dromaeosaurs . The arms are around half the length of the legs and over half the length of the presacral vertebral column . The hands are long, and tridactyl, with a reduced third finger in Caudipteryx and Ajancingenia . There are between 5 and 8 sacral vertebrae. The pubis
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1848-644: The two extremes, with alvarezsaurids and some avialans being insectivorous, and with advanced oviraptorosaurs and troodontids being omnivorous. A 2023 study analyzing fossil eggshells assigned to Troodon with clumped isotope thermometry found that Troodon , and likely other non-avian maniraptorans, had a slowed calcification of eggs akin to that of most reptiles. This contrasts with the rapid calcification of eggs found in modern birds, indicating that most maniraptorans aside from birds retained this basal trait. This would also indicate that most non-avian maniraptorans possessed two functional ovaries , contrasting with
1892-467: The wrist ( carpus ). In 2004, Tom Holtz and Halszka Osmólska pointed out six other maniraptoran characters relating to specific details of the skeleton. Unlike most other saurischian dinosaurs, which have pubic bones that point forward, several groups of maniraptorans have an ornithischian -like backwards-pointing hip bone. A backward-pointing hip characterizes the therizinosaurs , dromaeosaurids , avialans , and some primitive troodontids . The fact that
1936-951: Was found by an analysis published with the description of the caenagnathid Anzu . Incisivosaurus gauthieri Similicaudipteryx yixianensis Caudipteryx zoui Caudipteryx dongi Avimimus portentosus Microvenator celer Gigantoraptor erlianensis Caenagnathasia martinsoni Ojoraptorsaurus boerei Alberta dentary morph 3 Epichirostenotes curriei Elmisaurus rarus Hagryphus giganteus Chirostenotes pergracilis Leptorhynchos gaddisi Leptorhynchos elegans "Caenagnathus" sternbergi Anzu wyliei Caenagnathus collinsi Nankangia jiangxiensis Yulong mini Nomingia gobiensis Oviraptor philoceratops Rinchenia mongoliensis Zamyn Khondt oviraptorid Huanansaurus ganzhouensis Citipati osmolskae Citipati sp. Wulatelong gobiensis Banji long Shixinggia oblita Maniraptora Maniraptora
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