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46-535: Alxasaurus ( / ˌ ɑː l ʃ ə ˈ s ɔː r ə s / ; meaning " Alxa lizard") is a genus of therizinosauroid theropod dinosaurs from the Early Cretaceous ( Albian age) Bayin-Gobi Formation of Inner Mongolia . The fossil remains were first discovered in 1988 and described by the Canadian paleontologist Dale Russell and his Chinese colleague Dong Zhiming in 1993 or 1994. Although

92-504: A 2016 study published in the Journal of Geology suggested that the integumentary structures found on Kulindadromeus and Psittacosaurus may be highly deformed scales rather than filamentous feathers. Display feathers are also known from dinosaurs that are very primitive members of the bird lineage, or Avialae . The most primitive example is Epidexipteryx , which had a short tail with extremely long, ribbon-like feathers. Oddly enough,

138-544: A composition similar to that of feathers in modern birds. Crocodilians also possess beta keratin similar to those of birds, which suggests that they evolved from common ancestral genes. Shortly after the 1859 publication of Charles Darwin 's On the Origin of Species , the British biologist Thomas Henry Huxley proposed that birds were descendants of dinosaurs. He compared the skeletal structure of Compsognathus ,

184-456: A feathered dinosaur was Huxley's depiction in 1876 of a feathered Compsognathus , made to accompany a bird evolution lecture he delivered in New York, in which he speculated that the aforementioned dinosaur might have had feathers. A century later, during the dinosaur renaissance , paleoartists began to create modern restorations of highly active dinosaurs. In 1969, Robert T. Bakker drew

230-411: A forgery. Comparing the photograph of the specimen with another find, Chinese paleontologist Xu Xing came to the conclusion that it was composed of two portions of different fossil animals. His claim made National Geographic review their research and they too came to the same conclusion. In 2011, samples of amber were discovered to contain preserved feathers from 75 to 80 million years ago during

276-441: A running Deinonychus . His student Gregory S. Paul depicted non-avian maniraptoran dinosaurs with feathers and protofeathers, starting in the late 1970s. The first known specimen of Archaeopteryx , on the basis of which the genus was named, was an isolated feather, although whether or not it belongs to Archaeopteryx has been controversial. One of the earliest discoveries of possible feather impressions by non-avian dinosaurs

322-457: A single species and is thus of dubious utility. The following cladogram is based on the phylogenetic analysis conducted by Hartman et al., 2019: "Chilantaisaurus" zheziangensis Alxasaurus [REDACTED] [REDACTED] [REDACTED] Alxa League In the 2020 census, there were 262,361 inhabitants. Alxa is the least populated region of Inner Mongolia Autonomous Region. A number of residents have been relocated from

368-618: A small theropod dinosaur, and the "first bird " Archaeopteryx lithographica (both of which were found in the Upper Jurassic Bavarian limestone of Solnhofen ). He showed that, apart from its hands and feathers, Archaeopteryx was quite similar to Compsognathus . Thus Archaeopteryx represents a transitional fossil . In 1868, he published On the Animals which are most nearly intermediate between Birds and Reptiles , which made that case. The first restoration of

414-538: A whole is a subject of ongoing debate and research. It has been suggested that feathers had originally functioned as thermal insulation , as it remains their function in the down feathers of infant birds prior to their eventual modification in birds into structures that support flight. Since scientific research began on dinosaurs in the early 1800s, they were generally believed to be closely related to modern reptiles such as lizards . The word dinosaur itself, coined in 1842 by paleontologist Richard Owen , comes from

460-451: Is a trace fossil ( Fulicopus lyellii ) of the 195–199 million year old Portland Formation in the northeastern United States. Gierlinski (1996, 1997, 1998) and Kundrát (2004) have interpreted traces between two footprints in this fossil as feather impressions from the belly of a squatting dilophosaurid . Although some reviewers have raised questions about the naming and interpretation of this fossil, if correct, that early Jurassic fossil

506-460: Is already stated in Gould and Vrba (1982). The original benefit might have been metabolic. Feathers are largely made of the keratin protein complex, which has disulfide bonds between amino acids that give it stability and elasticity. The metabolism of amino acids containing sulfur can be toxic; however, if the sulfur amino acids are not catabolized as the final products of urea or uric acid but used for

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552-435: Is an increasing body of evidence that supports the display hypothesis, which states that early feathers were colored and increased reproductive success. Coloration could have provided the original adaptation of feathers, implying that all later functions of feathers, such as thermoregulation and flight, were co-opted . This hypothesis has been supported by the discovery of pigmented feathers in multiple species. Supporting

598-446: Is considered to exemplify the genus and species, is the largest and most complete of the five, consisting of the right dentary (lower jaw) with some teeth, 5 cervical vertebrae , 28 caudal vertebrae , 5 sacral vertebrae , 9 ribs , 15 chevrons , an isolated scapula , both coracoids , both humeri , isolated radius , both ulnae , a virtually complete manus , both ilia , both ischia and both femora . The other four specimens are

644-502: Is due to the different structural properties of feathers compared to fur. Some evidence also suggests that more derived feather types may have served as insulation. For instance, a study of oviraptorid pennaceous wing feathers and nesting posture suggests that elongated wing feathers evidently may have served to fill gaps between brooding individuals' insulatory body chamber and the outside environment. This "wall" of wing feathers could have shielded eggs from temperature extremes. There

690-429: Is not known with certainty in archosaur phylogeny that the earliest simple "protofeathers" arose, as well as whether they arose once or independently multiple times. Filamentous structures are clearly present in pterosaurs , and long, hollow quills have been reported in specimens of the ornithischian dinosaurs Psittacosaurus and Tianyulong although there has been disagreement. In 2009, Xu et al. noted that

736-522: Is not reflected in the salaries of the average low-skilled worker, which is on par with other mid-sized Chinese cities. Alxa is divided into three banners : Feathered dinosaur A feathered dinosaur is any species of dinosaur possessing feathers . That includes all species of birds , and in recent decades evidence has accumulated that many non-avian dinosaur species also possessed feathers in some shape or form. The extent to which feathers or feather-like structures were present in dinosaurs as

782-528: Is now thought to occupy a position between the early Beipiaosaurus and later therizinosaurids such as Erlikosaurus , Segnosaurus , or Therizinosaurus . Although Rusell and Dong coined the Alxasauridae to contain Alxasaurus , the family has not been widely corroborated in most analyses. In 2010, Lindsay E. Zanno noted that, while technically still valid, the group currently consists of only

828-573: Is one with a tuft of branched barbs without a rachis. At stage IV, differentiated distal and proximal barbules produce a closed, pennaceous vane (a contour feather ). A closed vane develops when pennulae on the distal barbules form a hooked shape to attach to the simpler proximal barbules of the adjacent barb. Stage V developmental novelties gave rise to additional structural diversity in the closed pennaceous feather. Here, asymmetrical flight feathers, bipinnate plumulaceous feathers, filoplumes, powder down, and bristles evolved. Some evidence suggests that

874-599: Is plausible that theropods would have had the visual acuity necessary to see the displays. In a study by Stevens (2006), the binocular field of view for Velociraptor has been estimated to be 55 to 60 degrees, which is about that of modern owls. Visual acuity for Tyrannosaurus has been predicted to be anywhere from about that of humans to 13 times that of humans. Paleontological and evolutionary developmental studies show that feathers or feather-like structures were converting back to scales. The idea that precursors of feathers appeared before they were co-opted for insulation

920-433: Is the first definitive discovery of dinosaur material in amber. Several non-avian dinosaurs are now known to have been feathered. Direct evidence of feathers exists for several species . In all examples, the evidence described consists of feather impressions, except those genera inferred to have had feathers based on skeletal or chemical evidence, such as the presence of quill knobs (the anchor points for wing feathers on

966-584: Is the oldest known evidence of feathers, almost 30 million years older than the next-oldest-known evidence. The most important discoveries at Liaoning have been a host of feathered dinosaur fossils, with a steady stream of new finds filling in the picture of the dinosaur–bird connection and adding more to theories of the evolutionary development of feathers and flight. Turner et al . (2007) reported quill knobs from an ulna of Velociraptor mongoliensis , and these are strongly correlated with large and well-developed secondary feathers. Behavioural evidence, in

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1012-828: The Cretaceous Period, with evidence that they were from both dinosaurs and birds. Initial analysis suggests that some of the feathers were used for insulation, and not flight. More complex feathers were revealed to have variations in coloration similar to modern birds, while simpler protofeathers were predominantly dark. Only 11 specimens are currently known. The specimens are too rare to be broken open to study their melanosomes (pigment-bearing organelles), but there are plans for using non-destructive high-resolution X-ray imaging. Melanosomes produce colouration in feathers; as differently-shaped melanosomes produce different colours, subsequent research on melanosomes preserved in feathered dinosaur specimens has led to reconstructions of

1058-582: The life appearance of several dinosaur species . These include Anchiornis , Sinosauropteryx , Microraptor , and Archaeopteryx . In 2016, the discovery was announced of a feathered dinosaur tail preserved in amber that is estimated to be 99 million years old. Lida Xing, a researcher from the China University of Geosciences in Beijing , found the specimen at an amber market in Myanmar . It

1104-427: The paratypes IVPP 88301, IVPP 88402 (small individual), IVPP 88501 (immature individual) and IVPP 88510. Together the specimens represent most of the species hypodigm aside from the skull . Several specimens are known and they vary in size, but Gregory S. Paul estimated its maximum adult length up to 4 m (13 ft) and mass up to 400 kg (880 lb). Alxasaurus is among the earliest known members of

1150-467: The 2000s and the 2010s, and technology enabled scientists to study fossils more closely. Among non-avian dinosaurs , feathers or feather-like integument have been discovered in dozens of genera via direct and indirect fossil evidence. Although the vast majority of feather discoveries have been in coelurosaurian theropods , feather-like integument has also been discovered in at least three ornithischians , suggesting that feathers may have been present on

1196-458: The Greek for 'terrible lizard'. That view began to shift during the so-called dinosaur renaissance in scientific research in the late 1960s; by the mid-1990s, significant evidence had emerged that dinosaurs were much more closely related to birds, which descended directly from the theropod group of dinosaurs. Knowledge of the origin of feathers developed as new fossils were discovered throughout

1242-837: The Inner Mongolia (Nei Mongol Zizhiqu) region of the People's Republic of China . The single known species , elesitaiensis , is named after Elesitai, a village found in this region, near which the fossil remains of Alxasaurus were located. Five Alxasaurus specimens were recovered from the Bayin-Gobi Formation of Inner Mongolia, which dates to the Albian stage of the Early Cretaceous Period, or about 113 million to 100.5 million years ago . The holotype specimen, IVPP 88402 (large individual), which

1288-524: The Therizinosauroidea, but it already possessed the body shape—including the long neck, short tail, and relatively large claws—of later therizinosauroids. Like other members of this group, it was a bipedal herbivore with a large gut to process plant material. While exhibiting many typical therizinosaur features in overall body shape and in the teeth, the skeleton of Alxasaurus also shows several features present in more typical theropods, and

1334-402: The basal neornithischian Kulindadromeus report that although the lower leg and tail seemed to be scaled, "varied integumentary structures were found directly associated with skeletal elements, supporting the hypothesis that simple filamentous feathers, as well as compound feather-like structures comparable to those in theropods, were widespread amongst the whole dinosaur clade." In contrast,

1380-460: The collar. The barb ridges on the anterior midline of the follicle fuse together, forming the rachis. The creation of a posterior barb locus follows, giving an indeterminate number of barbs. This resulted in a feather with a symmetrical, primarily branched structure with a rachis and unbranched barbs. In stage IIIb, barbules paired within the peripheral barbule plates of the barb ridges, create branched barbs with rami and barbules. This resulting feather

1426-500: The discovery of this animal provided significant evidence that therizinosaurs were aberrant theropods. Specifically, the semilunate carpal bone of the wrist is found only in maniraptoran theropods, which also include oviraptorosaurs , dromaeosaurs , troodontids , and birds . Even more basal therizinosaurs such as the feathered Beipiaosaurus and primitive Falcarius have since been discovered with more theropod features and have helped to solidify this arrangement. Alxasaurus

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1472-464: The display hypothesis is the fact that fossil feathers have been observed in a ground-dwelling herbivorous dinosaur clade, making it unlikely that feathers functioned as predatory tools or as a means of flight. Additionally, some specimens have iridescent feathers. Pigmented and iridescent feathers may have provided greater attractiveness to mates, providing enhanced reproductive success when compared to non-colored feathers. Current research shows that it

1518-528: The forelimb) or a pygostyle (the fused vertebrae at the tail tip which often supports large feathers). Integumentary structures that gave rise to the feathers of birds are seen in the dorsal spines of reptiles and fish. A similar stage in their evolution to the complex coats of birds and mammals can be observed in living reptiles such as iguanas and Gonocephalus agamids . Feather structures are thought to have proceeded from simple hollow filaments through several stages of increasing complexity, ending with

1564-563: The form of an oviraptorosaur on its nest, showed another link with birds. Its forearms were folded, like those of a bird. Although no feathers were preserved, it is likely that these would have been present to insulate eggs and juveniles. Not all of the Chinese fossil discoveries proved valid however. In 1999, a supposed fossil of an apparently feathered dinosaur named Archaeoraptor liaoningensis , also found in Liaoning, turned out to be

1610-651: The fossil does not preserve wing feathers, suggesting that Epidexipteryx was either secondarily flightless, or that display feathers evolved before flight feathers in the bird lineage. Plumaceous feathers are found in nearly all lineages of Theropoda common in the northern hemisphere, and pennaceous feathers are attested as far down the tree as the Ornithomimosauria . The fact that only adult Ornithomimus had wing-like structures suggests that pennaceous feathers evolved for mating displays. This technique, called phylogenetic bracketing , can also be used to infer

1656-558: The growing Tengger Desert . Since 2010, Alxa League has frequently appeared as one of the most prosperous prefecture-level divisions in all of China when measured by GDP per capita; in 2013, the GDP per head was approximately US$ 30,000. If using this measure alone, Alxa was ranked first in China, even higher than its neighbor Ordos . Wealth in the region is not evenly distributed, and the numbers are skewed by its low permanent population. Much of

1702-546: The hollow, unbranched, stiff integumentary structures found on a specimen of Beipiaosaurus were strikingly similar to the integumentary structures of Psittacosaurus and pterosaurs. They suggested that all of these structures may have been inherited from a common ancestor much earlier in the evolution of archosaurs, possibly in an ornithodire from the Middle Triassic or earlier. More recently, findings in Russia of

1748-433: The inner, basilar layer of the follicle collar differentiated into longitudinal barb ridges with unbranched keratin filaments, while the thin peripheral layer of the collar became the deciduous sheath, forming a tuft of unbranched barbs with a basal calamus. Stage III consists of two developmental novelties, IIIa and IIIb, as either could have occurred first. Stage IIIa involves helical displacement of barb ridges arising within

1794-412: The large, deeply rooted feathers with strong pens ( rachis ), barbs and barbules that birds display today. According to Prum's (1999) proposed model, at stage I, the follicle originates with a cylindrical epidermal depression around the base of the feather papilla. The first feather resulted when undifferentiated tubular follicle collar developed out of the old keratinocytes being pushed out. At stage II,

1840-467: The last common ancestor of the Ornithoscelida , a dinosaur group including both theropods and ornithischians. It is possible that feathers first developed in even earlier archosaurs , in light of the discovery of vaned feathers in pterosaurs . Fossil feathers from the dinosaur Sinosauropteryx contain traces of beta-proteins (formerly called beta-keratins), confirming that early feathers had

1886-623: The original function of simple feathers was insulation. In particular, preserved patches of skin in large, derived, tyrannosauroids show scutes , while those in smaller, more primitive, forms show feathers. This may indicate that the larger forms had complex skins, with both scutes and filaments, or that tyrannosauroids may be like rhinos and elephants , having filaments at birth and then losing them as they developed to maturity. An adult Tyrannosaurus rex weighed about as much as an African elephant . If large tyrannosauroids were endotherms , they would have needed to radiate heat efficiently. This

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1932-615: The paper is technically included in the last issue of the 1993 volume of the Canadian Journal of Earth Sciences , this issue was not actually released until February or March 1994. Alxasaurus is named after the Alxa Desert of Inner Mongolia, also known as the "Alashan" desert , and the name also includes the Greek word sauros ("lizard"). Alxa (or Alashan) is also the name of the league , or administrative division , of

1978-524: The productive economic activity takes place under the auspices of several large companies operating in the region, extracting natural resources. These include China Kingho Corporation, a " clean coal " technology operator, and the Inner Mongolia-based Taiximei Group . Due to its remote location, much of the economic activity takes place with the support of migrant laborers from other parts of China. The high per capita GDP

2024-404: The synthesis of keratin instead, the release of hydrogen sulfide is extremely reduced or avoided. For an organism whose metabolism works at high internal temperatures of 40 °C (104 °F) or greater, it can be extremely important to prevent the excess production of hydrogen sulfide. This hypothesis could be consistent with the need for high metabolic rate of theropod dinosaurs. The point

2070-1426: The time of writing, some of which have fossil evidence of scales. The presence or lack of feathered specimens in a given clade does not confirm that all members in a clade have the specified integument, unless corroborated with representative fossil evidence within clade members. Dilophosauridae Megalosauroidea Carnosauria Sciurumimus – filamentous feathers Tyrannosauroidea ( Dilong , Yutyrannus ) – plumulaceous feathers Sinocalliopteryx – plumulaceous feathers Compsognathidae ( Sinosauropteryx , GMV 2124 ) – plumulaceous feathers Juravenator – filamentous feathers Ornitholestes Ornithomimosauria ( Ornithomimus , Deinocheirus ) – plumulaceous feathers Alvarezsauridae ( Shuvuuia ) – plumulaceous feathers Therizinosauroidea ( Beipiaosaurus , Jianchangosaurus ) – plumulaceous feathers Oviraptorosauria ( Avimimus , Nomingia , Caudipteryx , Similicaudipteryx , Protarchaeopteryx , Ningyuansaurus , Citipati , Conchoraptor ) – pennaceous feathers Scansoriopterygidae ( Scansoriopteryx , Epidexipteryx ) – pennaceous feathers Eosinopteryx – pennaceous feathers Dromaeosauridae ( Sinornithosaurus , Microraptor , Velociraptor , Changyuraptor ) – pennaceous feathers Troodontidae ( Jinfengopteryx ) – pennaceous feathers Avialae (ancestors of birds) The following cladogram

2116-404: The type of feathers a species may have had, since the developmental history of feathers is now reasonably well-known. All feathered species had filamentaceous or plumaceous (downy) feathers, with pennaceous feathers found among the more bird-like groups. The following cladogram is adapted from Godefroit et al. , 2013. Grey denotes a clade that is not known to contain any feathered specimen at

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