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136-611: Incisivosaurus ("incisor lizard") is a genus of small, probably herbivorous theropod dinosaurs from the early Cretaceous Period of what is now the People's Republic of China . The first specimen to be described (by Xu et al. in 2002), IVPP V13326, is a skull that was collected from the lowermost levels (the fluvial Lujiatun beds) of the Yixian Formation (dating to the Barremian stage about 126 million years ago) in

272-459: A Confuciusornis skeleton preserving an egg near its right foot – the first possible egg referable to the genus. The skeleton is from the short-tailed form and thus might represent a female. The egg might have fallen out of the body after the death of the presumed female, although it cannot be excluded that this association of an adult with an egg was only by chance. The egg is roundish in shape and measures 17 mm in diameter, slightly smaller than

408-422: A pygostyle (a bone formed from a series of short, fused tail vertebrae) and a bony sternum (breastbone), but more basal or "primitive" than modern birds in retaining large claws on the forelimbs, having a primitive skull with a closed eye-socket, and a relatively small breastbone. At first the number of basal characteristics was exaggerated: Hou assumed in 1995 that a long tail was present and mistook grooves in

544-666: A 2010 paper, Gareth Dyke and Kaiser showed that the breadth of the Confuciusornis egg was indeed smaller than what would be expected for a modern bird of similar size. In a 2016 book, Luis Chiappe and Meng Qingjin stated that the aperture of a large specimen (DNHM-D 2454) indicates a maximum egg diameter of 23 millimetres (0.91 in). In modern birds, proportionally large eggs are commonly found in species whose hatchlings do fully depend on their parents ( altriciality ), while smaller eggs are often found in species whose hatchlings are more developed and independent ( precociality ). As

680-537: A 2016 review by David Varricchio and Frankie Jackson argued that nesting above the ground evolved only at a much later stage, within Neornithes, and that Mesozoic birds would have buried their eggs on the ground, either fully or partially, as seen in non-avian dinosaurs. Growth can be reconstructed based on the inner bone structure. The first such study on Confuciusornis , presented by Fucheng Zhang and colleagues in 1998, used scanning electron microscopy to analyze

816-438: A central keel, a strut-like coracoid, a large deltopectoral crest, a strong ulna (forearm bone) and an enlarged second metacarpal. The sternal keel and deltopectoral crest (which provides a more powerful upstroke) are adaptations to flapping flight in modern birds, indicating that Confuciusornis may have been capable of the same. However, it may have had a different flight stroke due to being incapable of rotating its arm behind

952-597: A defense mechanism, a method used by several extant species. Such shedding would have been triggered by stress induced by the very volcanic explosions that buried the animals, resulting in a large number of specimens lacking these feathers. In a 2011 paper, Jesús Marugán-Lobón and colleagues stated that even the presence of two separate species, one with and one without long tail feathers, needs to be considered. This possibility would be, however, unsubstantiated at present, as other anatomical differences between these possible species are not apparent. In 2007, Gary Kaiser mentioned

1088-410: A femur in cross section. Because the bone was well vascularized (contained many blood vessels) and showed only a single line of arrested growth (growth ring), these authors determined that growth must have been fast and continuous as in modern birds, and that Confuciusornis must have been endothermic . Zhang and colleagues corroborated this claim in a subsequent paper, stating that the bone structure

1224-495: A fossil Confuciusornis specimen, IVPP V13171. They reported the presence of melanosomes were of two types: eumelanosomes and pheomelanosomes . This indicated that Confuciusornis had hues of grey, red/brown and black, possibly something like the modern zebra finch . It was also the first time an early bird fossil has been shown to contain preserved pheomelanosomes. However, a second research team failed to find these reported traces of pheomelanosomes. Their 2011 study also found

1360-428: A fragmentary hind limb together with six feather impressions attached to both sides of the tibia (shin bone). It was soon noted that the two paratype specimens only comprise bones that are unknown from the holotype, and that this lack of overlap makes their referral to the species speculative. Only the discovery of a great number of well-preserved specimens shortly after had confirmed that the specimens indeed represent

1496-427: A function in reproduction at all. Several alternative hypotheses explaining the frequent absence of long tail feathers have been proposed. In their 1999 study, Chiappe and colleagues discussed the possibility that individuals might lack tail feathers because they died during molting . Although direct evidence for molting in early birds is missing, the lack of feather abrasion in Confuciusornis specimens suggests that

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1632-407: A genus is determined by taxonomists . The standards for genus classification are not strictly codified, so different authorities often produce different classifications for genera. There are some general practices used, however, including the idea that a newly defined genus should fulfill these three criteria to be descriptively useful: Moreover, genera should be composed of phylogenetic units of

1768-651: A later homonym of a validly published name is a nomen illegitimum or nom. illeg. ; for a full list refer to the International Code of Nomenclature for algae, fungi, and plants and the work cited above by Hawksworth, 2010. In place of the "valid taxon" in zoology, the nearest equivalent in botany is " correct name " or "current name" which can, again, differ or change with alternative taxonomic treatments or new information that results in previously accepted genera being combined or split. Prokaryote and virus codes of nomenclature also exist which serve as

1904-416: A link between the presence of certain metals, like copper , and preserved melanin . Using a combination of fossil impressions of melanosomes and the presence of metals in the feathers, the second team of scientists reconstructed Confuciusornis with darkly colored body feathers and upper wing feathers, but found no trace of either melanosomes or metals in the majority of the wing feathers. They suggested that

2040-615: A local flea market. In December, Hou learned about a second specimen, which had been discovered by a farmer named Yang Yushan. Both specimens were found in the same locality in Shangyuan, Beipiao . In 1995, these two specimens, as well as a third one, were formally described as a new genus and species of bird, Confuciusornis sanctus , by Hou and colleagues. The generic name combines the philosopher Confucius with Greek ὄρνις ( ornis ), "bird". The specific name means "holy one" in Latin and

2176-628: A long time and redescribed as new by a range of subsequent workers, or if a range of genera previously considered separate taxa have subsequently been consolidated into one. For example, the World Register of Marine Species presently lists 8 genus-level synonyms for the sperm whale genus Physeter Linnaeus, 1758, and 13 for the bivalve genus Pecten O.F. Müller, 1776. Within the same kingdom, one generic name can apply to one genus only. However, many names have been assigned (usually unintentionally) to two or more different genera. For example,

2312-430: A more "primitive" skull than Archaeopteryx , but it is the first known bird to have lost the long tail of Archaeopteryx and develop fused tail vertebrae, a pygostyle . One controversial study concluded that Confuciusornis may be more closely related to Microraptor and other dromaeosaurids than to Archaeopteryx , but this study was criticized on methodological grounds. The present standard interpretation of

2448-437: A pioneer of the phylogenetic method of classification. The initial description of Incisivosaurus by Xu et al. showed that the skull, which measures approximately 10 cm (3.9 in) in length, preserves the most complete dentition known for any oviraptorosaurian . Their cladistic analysis indicated that Incisivosaurus lies at the base of the oviraptorosaurian group, making it more primitive than Caudipteryx and

2584-743: A portion of these fossils have been added to the collections of Chinese research institutions, more have probably been smuggled out of the country. In 1999, it was estimated that the National Geological Museum of China in Beijing housed nearly 100 specimens of Confuciusornis , and in 2010, the Shandong Tianyu Museum of Nature was reported to possess 536 specimens of the bird. The majority of specimens, however, are held privately and thus are not available for research. At one time forty individuals were discovered on

2720-409: A reference for designating currently accepted genus names as opposed to others which may be either reduced to synonymy, or, in the case of prokaryotes, relegated to a status of "names without standing in prokaryotic nomenclature". An available (zoological) or validly published (botanical) name that has been historically applied to a genus but is not regarded as the accepted (current/valid) name for

2856-466: A single species. Together with the early mammal Zhangheotherium , which was discovered at around the same time, Confuciusornis was considered to be the most remarkable fossil discovery of the Jehol Biota , which in the next decades would reveal the most important record of Mesozoic birds worldwide. In the late 1990s, Confuciusornis was thought to be both the oldest beaked bird as well as

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2992-440: A species. In the case of Confuciusornis , only C. sanctus is universally accepted. In 2002 Hou named the genus Jinzhouornis , but Chiappe et al. (2018) and Wang et al. (2018) showed that this genus is a junior synonym of Confuciusornis based on morphometry and examination of known confuciusornithiform specimens. Confuciusornis was about the size of a modern crow , with a total length of 50 centimetres (1.6 feet) and

3128-432: A squirrel. Daniel Hembree, however, while acknowledging that tree climbing was likely, pointed out that the rump was apparently not lifted more than 25° relative to the femur in vertical position, as shown by the location of the antitrochanter in the hip joint. Dieter S. Peters considered it very unlikely that Confuciusornis climbed trunks as turning the thumb claw inwards would stretch the very long wing forwards, right in

3264-415: A straight airfoil . This collectively is strongly indicative that Confuciusornis was capable of powered flight, if not only for short periods of time. Many specimens of Confuciusornis preserve a single pair of long, streamer-like tail feathers, similar to those present in some modern birds-of-paradise . Specimens lacking these feathers include ones that otherwise have exquisitely preserved feathers on

3400-426: A structure identical to that seen in the fossil. Later, the rest of the sheath falls away when the entire feather has fully developed. Prum also noted, as did Xu and his team, that the structure of the oviraptorosaur feathers is fundamentally different from other prehistoric birds with ribbon-like tail feathers. In those other species, the ribbon portion is formed from a flattened and expanded rachis, or central quill, of

3536-570: A surface of about 100 m . This has been explained as the result of entire flocks of birds being simultaneously killed by ash, heat or poisonous gas following the volcanic eruptions that caused the tuff stone in which the fossils were found to be deposited as lake sediments . Since the description of Confuciusornis sanctus , five additional species have been formally named and described. As with many other fossil genera, species are difficult to define, as differences between species can often not be readily distinguished from variation that occurs within

3672-427: A taxon; however, the names published in suppressed works are made unavailable via the relevant Opinion dealing with the work in question. In botany, similar concepts exist but with different labels. The botanical equivalent of zoology's "available name" is a validly published name . An invalidly published name is a nomen invalidum or nom. inval. ; a rejected name is a nomen rejiciendum or nom. rej. ;

3808-500: A toothless beak, but closer and later relatives of modern birds such as Hesperornis and Ichthyornis were toothed, indicating that the loss of teeth occurred convergently in Confuciusornis and living birds. It was thought to be the oldest known bird to have a beak, though this title now belongs to an earlier relative Eoconfuciusornis . It was named after the Chinese moral philosopher Confucius (551–479 BC). Confuciusornis

3944-455: A total of c. 520,000 published names (including synonyms) as at end 2019, increasing at some 2,500 published generic names per year. "Official" registers of taxon names at all ranks, including genera, exist for a few groups only such as viruses and prokaryotes, while for others there are compendia with no "official" standing such as Index Fungorum for fungi, Index Nominum Algarum and AlgaeBase for algae, Index Nominum Genericorum and

4080-514: A very strong bite force similar to ornithomimosaurs 33 times its weight. The moderate jaw gape seen in oviraptorosaurs is indicative of herbivory, but it is clear they were feeding on much tougher vegetation than other herbivorous theropods in their environment, such as ornithomimosaurs and therizinosaurs. The examinations suggest oviraptorosaurs may have been powerful-biting generalists or specialists that partook of niche partitioning both in body size and jaw function. Genus The composition of

4216-413: A wingspan of up to 70 cm (2.3 ft). Its body weight has been estimated to have been as much as 0.5 kilograms (1.1 lb), or as little as 0.2 kg (0.44 lb). C. feducciai was about a third longer than average specimens of C. sanctus . Confuciusornis shows a mix of basal and derived traits. It was more "advanced" or derived than Archaeopteryx in possessing a short tail with

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4352-417: Is a translation of Chinese 圣贤 ( shèngxián) , "sage", again in reference to Confucius. The first discovered specimen was designated the holotype and catalogued under the specimen number IVPP V10918; it comprises a partial skeleton with skull and parts of the forelimb. Of the other two skeletons, one ( paratype , IVPP V10895) comprises a complete pelvis and hind limb, and the other (paratype, IVPP V10919–10925)

4488-416: Is commonly found as large assemblages in lake bottom sediments with little to no evidence of extensive postmortem transport, and that it would be highly unusual for gliding animals to be found in such large numbers in deep water. Rather, this evidence suggests that Confuciusornis traveled in large flocks over the lake surfaces, a habitat consistent with a flying animal. A number of researchers have questioned

4624-429: Is consistent with either birds that live in dense forests or gliding birds; the former is consistent with its environment being densely forested, and requiring more maneuverability and stability than speed. The substantial propatagium would have produced a generous amount of lift, while the likewise large postpatagium would have provided a large attachment area for the calami of the feathers, which would have kept them as

4760-612: Is discouraged by both the International Code of Zoological Nomenclature and the International Code of Nomenclature for algae, fungi, and plants , there are some five thousand such names in use in more than one kingdom. For instance, A list of generic homonyms (with their authorities), including both available (validly published) and selected unavailable names, has been compiled by the Interim Register of Marine and Nonmarine Genera (IRMNG). The type genus forms

4896-594: Is one of the most abundant vertebrates found in the Yixian Formation, and several hundred complete specimens have been found. In November 1993, the Chinese paleontologists Hou Lianhai and Hu Yoaming of the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) at Beijing , visited fossil collector Zhang He at his home in Jinzhou , where he showed them a fossil bird specimen that he had bought at

5032-460: Is somewhat arbitrary. Although all species within a genus are supposed to be "similar", there are no objective criteria for grouping species into genera. There is much debate among zoologists about whether enormous, species-rich genera should be maintained, as it is extremely difficult to come up with identification keys or even character sets that distinguish all species. Hence, many taxonomists argue in favor of breaking down large genera. For instance,

5168-474: Is the type species , and the generic name is permanently associated with the type specimen of its type species. Should the specimen turn out to be assignable to another genus, the generic name linked to it becomes a junior synonym and the remaining taxa in the former genus need to be reassessed. In zoological usage, taxonomic names, including those of genera, are classified as "available" or "unavailable". Available names are those published in accordance with

5304-547: Is the assessment that due to the lack of a keeled sternum and a high acrocoracoid, the musculus pectoralis minor could not serve as a M. supracoracoideus lifting the humerus via a tendon running through a foramen triosseum . This, coupled with a limited upstroke caused by a lateral position of the shoulder joint, would have made it difficult to gain altitude. Some authors, therefore, proposed that Confuciusornis used its large thumb claws to climb tree trunks. Martin assumed that it could raise its torso almost vertically like

5440-448: Is the most likely explanation for the presence and absence of long tail feathers. Winfried and Dieter Peters, however, responded in 2009 that both sexes likely had long tail feathers, as is the case in most modern birds that show similar feathers. One of the sexes, however, would have been larger than the other (sexual size dimorphism). These researchers further suggested that the distribution of size and long tail feathers in Confuciusornis

5576-539: The IVPP from 1997 onwards; recovered fossils include several hundred specimens of Confuciusornis . Many additional sites producing fossils of the Jehol biota have been recognized since, distributed over a large region including Liaoning, Hebei, and Inner Mongolia. Due to the great abundance, preservation, and commercial value of the fossils, excavations by local farmers produced an unusually high number of fossils. Although

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5712-621: The International Code of Zoological Nomenclature ; the earliest such name for any taxon (for example, a genus) should then be selected as the " valid " (i.e., current or accepted) name for the taxon in question. Consequently, there will be more available names than valid names at any point in time; which names are currently in use depending on the judgement of taxonomists in either combining taxa described under multiple names, or splitting taxa which may bring available names previously treated as synonyms back into use. "Unavailable" names in zoology comprise names that either were not published according to

5848-824: The International Plant Names Index for plants in general, and ferns through angiosperms, respectively, and Nomenclator Zoologicus and the Index to Organism Names for zoological names. Totals for both "all names" and estimates for "accepted names" as held in the Interim Register of Marine and Nonmarine Genera (IRMNG) are broken down further in the publication by Rees et al., 2020 cited above. The accepted names estimates are as follows, broken down by kingdom: The cited ranges of uncertainty arise because IRMNG lists "uncertain" names (not researched therein) in addition to known "accepted" names;

5984-419: The nomenclature codes , which allow each species a single unique name that, for animals (including protists ), plants (also including algae and fungi ) and prokaryotes ( bacteria and archaea ), is Latin and binomial in form; this contrasts with common or vernacular names , which are non-standardized, can be non-unique, and typically also vary by country and language of usage. Except for viruses ,

6120-577: The oviraptorids . A subsequent study by Osmolska et al. in 2004 described the distinguishing skeletal features of Incisivosaurus , including a long snout that made up about half the total length of the skull, a slender lower jaw with a long fenestra (opening), and its distinctive, large, flattened front teeth. In addition to these unique features, Incisivosaurus shared many traits with more typical oviraptorosaurs, allowing its classification with that group. Several features, including its numerous teeth (most advanced oviraptorids were toothless), show that it

6256-613: The phylogenetic position of Confuciusornis can be shown in this cladogram : Archaeopteryx Jeholornis Sapeornis Confuciusornis Changchengornis Enantiornithes Ornithuromorpha (including the Neornithes ) A close relative, the confuciusornithid Changchengornis hengdaoziensis , also lived in the Yixian Formation. Changchengornis also possessed the paired, long tail feathers, as did several more advanced enantiornith birds. True, mobile tail fans only appeared in ornithuromorph birds, and possibly in

6392-404: The platypus belongs to the genus Ornithorhynchus although George Shaw named it Platypus in 1799 (these two names are thus synonyms ) . However, the name Platypus had already been given to a group of ambrosia beetles by Johann Friedrich Wilhelm Herbst in 1793. A name that means two different things is a homonym . Since beetles and platypuses are both members of the kingdom Animalia,

6528-434: The scleral rings supporting the eyes of Confuciusornis and modern birds and other reptiles indicate that it may have been diurnal , similar to most modern birds. Confuciusornis has traditionally been assumed to have been a competent flier based on its extremely long wings with strongly asymmetrical feathers. Other adaptations for improved flight capabilities include: a fused wrist, a short tail, an ossified sternum with

6664-413: The Chinese fossil material with a differing rachis diameter. In 2016, Falk et al. argued in favor of flight capabilities for Confuciusornis using evidence from laser fluorescence of two soft tissue-preserving specimens. They found that, contrary to Nudds and Dyke's assertions, the raches of Confuciusornis were relatively robust, with a maximum width of over 1.5 mm (0.059 in). The wing shape

6800-592: The Enantiornithes were closely related. In 2001, Ji Qiang suggested an alternative position as the sister taxon of the Ornithothoraces . In 2002 Ji's hypothesis was confirmed by a cladistic analysis by Chiappe, who defined a new group: the Pygostylia of which Confuciusornis is by definition the most basal member. Several traits of Confuciusornis show its position in bird evolution; it has

6936-462: The Sihetun area, near Beipiao City , in western Liaoning Province. The most significant, and highly unusual, characteristic of this dinosaur is its apparent adaptation to an herbivorous or omnivorous lifestyle. It was named for its prominent, rodent -like front teeth, which show wear patterns commonly found in plant-eating dinosaurs. The specific name gauthieri honors Dr. Jacques Gauthier ,

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7072-429: The above interpretation of the feathers in a November 2010 letter to the journal Nature . Prum noted that the apparently ribbon-like structure of the juvenile's feathers were consistent with pennaceous feathers in the midst of moulting. In modern birds, new vaned feathers emerge from the feather follicle enclosed in a "pin feather", a solid tube covered in keratin. Usually, the tip of this tube will fall away first, leaving

7208-453: The animal aged, and replaced with more modern-style barbed feathers. The primary feathers grew more slowly than the tail feathers, not reaching equal size until the animal was close to maturity, and the secondary feathers would not appear at all until this more mature stage. This suggests that the wing feathers had little use at a young age, only becoming fully developed with maturity. However, feather development specialist Richard Prum disputed

7344-417: The animal was close to maturity, and the secondary feathers would not appear at all until this more mature stage. This suggests that the wing feathers had little use at a young age, only becoming fully developed with maturity. Additionally, the youngest specimen's vaned feathers appeared to lack barbs except at the tip, instead consisting of a solid sheet. Xu and colleagues interpreted the stark differences in

7480-442: The base for higher taxonomic ranks, such as the family name Canidae ("Canids") based on Canis . However, this does not typically ascend more than one or two levels: the order to which dogs and wolves belong is Carnivora ("Carnivores"). The numbers of either accepted, or all published genus names is not known precisely; Rees et al., 2020 estimate that approximately 310,000 accepted names (valid taxa) may exist, out of

7616-486: The body, and its relatively smaller sternal keel indicates that it likely was not capable of flight for extended periods of time. Several contrary claims have been made against that the flight capabilities of Confuciusornis . The first of these regarded problems to attain a steep flight path due to a limited wing amplitude. In Senter's interpretation of the position of the shoulder joint, a normal upstroke would be impossible precluding flapping flight entirely. Less radical

7752-434: The braincase wall, making its exact borders impossible to determine, which is also true for adult modern birds. Various interpretations have been proposed of the morphology and identity of the bones in the temporal region behind the orbits, but it may not be resolvable with the available fossils. Confuciusornis was considered the first known bird with an ancestral diapsid skull (with two temporal fenestrae on each side of

7888-434: The correctness of the rachis measurements, stating that the specimens they had studied showed a shaft thickness of 2.1–2.3 millimetres (0.083–0.091 in), compared to 1.2 mm (0.047 in) as reported by Nudds and Dyke. Nudd and Dyke replied that, apart from the weight aspect, such greater shaft thickness alone would make flapping flight possible; however, they allowed for the possibility of two species being present in

8024-434: The cotyla (which connected with the condyle of the upper jaw), and this part was therefore similar to a retroarticular process as seen in other taxa. The surangular enclosed two mandibular fenestrae. The hindmost part of the surangular had a small foramen placed in the same position as similar openings in the mandibles of non-bird theropods and modern birds. The splenial bone was three-pronged (as in some modern birds, but unlike

8160-412: The earlier histological findings of de Ricqlès that suggest a much shorter, avian-style growth. Alternatively, the observed size distribution might also be explained by the presence of more than one species, although there are no anatomical features that could be correlated with these potential species. It could also be explained by assuming an attritional death assemblage, in which mortality rates (and thus

8296-448: The earliest bird after Archaeopteryx . It was also considered to be only slightly younger than Archaeopteryx – the Yixian Formation , the rock unit where most Confuciusornis specimens have been found, was thought to be of Late Jurassic ( Tithonian ) age at the time. Although two bird genera, Sinornis and Cathayornis , had already described from the Jehol biota in 1992, these were only based on fragmentary remains and stem from

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8432-411: The enantiornithine Shanweiniao . The large, fleshy phalangeal foot pads, small interphalangeal foot pads, presence of only reticulate scales on the underside of the foot (which increases flexibility), and curved foot claws of Confuciusornis are all traits shared with modern tree-dwelling , perching birds, suggesting that Confuciusornis may have had a similar lifestyle. Comparisons between

8568-526: The estimated egg of the specimen would have been around 30% smaller than expected for a modern altricial bird, it is likely that Confuciusornis was precocial. A 2018 study by Charles Deeming and Gerald Mayr measured the size of the pelvic canal of various Mesozoic birds including Confuciusornis to estimate egg size, concluding that eggs would have been small in proportion to body mass for Mesozoic birds in general. These researchers further posit that an avian-style contact incubation (sitting on eggs for breeding)

8704-544: The evolutionary line leading to modern birds. This view was contested by subsequent studies, which pointed out that slow growing bone is not necessarily an indicator for low metabolic rates, and in the case of Mesozoic birds was rather a result of the decrease in body size that characterized the early evolution of birds. A more comprehensive study based on thin sectioning of bones was published by Armand de Ricqlès and colleagues in 2003. Based on 80 thin sections taken from an adult Confuciusornis exemplar, this study confirmed

8840-461: The extremely fast growth characteristic for modern birds (6–8 weeks), suggesting that that growth was secondarily accelerated later in avian evolution. In 2008 Chiappe and colleagues conducted a statistical analysis based on 106 specimens to explore the relationship between body size and the possession of long tail feathers. The population showed a clear bimodal distribution of the size of the animals with two distinct weight classes . However, there

8976-407: The feather ligaments. Many specimens preserve a pair of long, narrow tail feathers, which grew longer than the entire length of the rest of the body. Unlike the feathers of most modern birds, these feathers were not differentiated into a central quill and barbs for most of their length. Rather, most of the feather formed a ribbon-like sheet, about six millimetres wide. Only at the last one quarter of

9112-582: The feather, towards the rounded tip, does the feather become differentiated into a central shaft with interlocking barbs. Many individuals of Confuciusornis lacked even these two tail feathers, possibly due to sexual dimorphism . The rest of the tail around the pygostyle was covered in short, non-aerodynamic feather tufts similar to the contour feathers of the body, rather than the familiar feather fan of modern bird tails. Laser fluorescence of two Confuciusornis specimens revealed additional details of their soft-tissue anatomy. The pro patagium of Confuciusornis

9248-516: The feather, with the feather barbs expanding out at the tip. In the fossil specimen, however, the "ribbon" like portion is the same width as the vaned tip. This is consistent with what is seen in feathers in the process of moulting. Prum concluded that rather than representing an instance of feathers changing in form as the animal aged, this specimen represents the first known fossil evidence of feather moulting. Prum also noted that in modern birds, tail feathers moult sequentially, not simultaneously as in

9384-437: The feathers of the two specimens as primarily age-related. They speculated that hatchlings would have been covered in natal down like modern birds. As the animal aged, the down would be replaced by vaned pennaceous feathers on the hands and tail, but ribbon-like and primitive in form, similar to the tail feathers of Confuciusornis , Epidexipteryx , and some enantiornithines . These feathers would be lost through moulting as

9520-416: The first finger to the contrary was very large and curved. The stub-like third metacarpal, which supported the calami of the feathers, was probably enclosed in the flesh of the hand. The formula of the finger phalanges was 2-3-4-0-0. The pelvis was connected to a sacrum formed by seven sacral vertebrae . The pubis was strongly pointing backwards. The left and right ischia were not fused. The femur

9656-446: The form "author, year" in zoology, and "standard abbreviated author name" in botany. Thus in the examples above, the genus Canis would be cited in full as " Canis Linnaeus, 1758" (zoological usage), while Hibiscus , also first established by Linnaeus but in 1753, is simply " Hibiscus L." (botanical usage). Each genus should have a designated type , although in practice there is a backlog of older names without one. In zoology, this

9792-494: The front half of the synsacrum were excavated at their sides, comparable to the back vertebrae. Robust side processes connected the synsacrum to the ilia of the pelvis. Although earlier descriptions had counted four or five "free", not fused, tail vertebrae, Chiappe e.a. in 1999 reported seven of them. These had round and somewhat concave front articulation facets. Their spinal processes were high and transversely compressed. The side processes were robust and stick out horizontally to

9928-737: The generic name (or its abbreviated form) still forms the leading portion of the scientific name, for example, Canis lupus lupus for the Eurasian wolf subspecies, or as a botanical example, Hibiscus arnottianus ssp. immaculatus . Also, as visible in the above examples, the Latinised portions of the scientific names of genera and their included species (and infraspecies, where applicable) are, by convention, written in italics . The scientific names of virus species are descriptive, not binomial in form, and may or may not incorporate an indication of their containing genus; for example,

10064-480: The hand, but this digit appears to have been free of feathers and independent of the body of the wing in Confuciusornis . According to Dieter Stefan Peters, to compensate for the lack of an alula, the third finger might have formed a separate winglet below the main wing, functioning like the flap of an aircraft. Despite the relatively advanced and long wing feathers, the forearm bones lacked any indication of quill knobs ( papillae ulnares ), or bony attachment points for

10200-417: The head of the animal; according to Kaiser, it would have fit precisely through the pelvic canal of the bird. In dinosaurs and Mesozoic birds, the width of the pelvic canal was restricted due to connection of the lower ends of the pubic bones, resulting in a V-shaped bony aperture through which eggs must fit. In modern birds, this connection of the pubic bones is lost, presumably allowing for larger eggs. In

10336-404: The high growth rates proposed by Zhang and colleagues. The fast-growing fibrolamellar bone tissue was similar to that seen in non-avian theropods, and the sampled individual probably reached adult size in much less than 20 weeks. Small body size was not primarily achieved by slowing growth but by shortening the period of rapid growth. The growth rate estimated for Confuciusornis is still lower than

10472-409: The jaw bones for small degenerated teeth. The skull morphology of Confuciusornis has been difficult to determine, due to the crushed and deformed nature of the fossils. The skull was near triangular in side view, and the toothless beak was robust and pointed. The front of the jaws had deep neurovascular foramina and grooves, associated with the keratinous rhamphotheca (horn-covered beak). The skull

10608-633: The largest component, with 23,236 ± 5,379 accepted genus names, of which 20,845 ± 4,494 are angiosperms (superclass Angiospermae). By comparison, the 2018 annual edition of the Catalogue of Life (estimated >90% complete, for extant species in the main) contains currently 175,363 "accepted" genus names for 1,744,204 living and 59,284 extinct species, also including genus names only (no species) for some groups. The number of species in genera varies considerably among taxonomic groups. For instance, among (non-avian) reptiles , which have about 1180 genera,

10744-441: The length of the hand and relatively longer than those of any living bird, while the secondary feathers of the lower arm were rather short by comparison. The outermost primary was much shorter than the second outermost primary, creating a relatively round, broad wing. Its wing shape does not specifically match any particular shape found among living birds. The primary feathers were asymmetrical to varying degrees, and especially so in

10880-559: The lizard genus Anolis has been suggested to be broken down into 8 or so different genera which would bring its ~400 species to smaller, more manageable subsets. Confuciusornis Confuciusornis is a genus of basal crow -sized avialan from the Early Cretaceous Period of the Yixian and Jiufotang Formations of China, dating from 125 to 120 million years ago. Like modern birds, Confuciusornis had

11016-404: The lower end of the postorbital process. This scaffolding consisted of two bony bridges, the temporal bar and the orbitozygomatic junction, which gave the appearance of the temporal opening being divided similarly to diapsid skulls, though this structure is comparable to bridges over the temporary fossa in modern birds. The mandible (lower jaw) is one of the best preserved parts of the skull. It

11152-475: The lower jaw connected) of the dentary was very robust. The lower margin formed an angle at the level of the front margin of the nasal foramen, which indicates how far back the rhamphotheca of the beak extended. The dentary had three processes that extended backwards into other bones placed further back in the mandible. The articular bone at the back of the mandible was completely fused with the surangular and prearticular bones. The mandible extended hindwards beyond

11288-451: The maxilla. The orbit was large, round, and contained sclerotic plates (the bony support inside the eye). A crescent-shaped element that formed the front wall of the orbit may be an ethmoidolacrimal complex similar to that of pigeons , but the identity of these bones is unclear due to bad preservation, and the fact that this region is very variable in modern birds. The external nares (bony nostrils) were near triangular and positioned far from

11424-403: The most (>300) have only 1 species, ~360 have between 2 and 4 species, 260 have 5–10 species, ~200 have 11–50 species, and only 27 genera have more than 50 species. However, some insect genera such as the bee genera Lasioglossum and Andrena have over 1000 species each. The largest flowering plant genus, Astragalus , contains over 3,000 species. Which species are assigned to a genus

11560-477: The most birdlike features of oviraptorosaurs may have been convergent with birds. Incisivosaurus is assumed to have been feathered like most other maniraptoran theropods. Its total body length has been estimated at 0.8–1 meter (2.6–3.3 feet) and its weight at 2–4.6 kg (4.4–10 lbs). In 2010, two feathered oviraptorosaur specimens were described, both of which preserved feather traces. These specimens (both juveniles, though one closer to maturity than

11696-428: The name could not be used for both. Johann Friedrich Blumenbach published the replacement name Ornithorhynchus in 1800. However, a genus in one kingdom is allowed to bear a scientific name that is in use as a generic name (or the name of a taxon in another rank) in a kingdom that is governed by a different nomenclature code. Names with the same form but applying to different taxa are called "homonyms". Although this

11832-420: The orbits (eye openings) like in modern birds, but unlike Archaeopteryx and other primitive birds without pygostyles, where these processes end in front of the orbits. The maxilla (the second large bone of the upper jaw) and premaxilla articulated by an oblique suture, and the maxilla had an extensive palatal shelf. The nasal bone was smaller than in most birds, and had a slender process that directed down towards

11968-462: The other) showed that the feathers were similar to the related Caudipteryx , with long (symmetrical) vaned feathers on the hand and tail, and the rest of the body covered in simpler, downy feathers. Though initially interpreted as specimens of Similicaudipteryx , later research suggested that they could instead be referred to Incisivosaurus . The nature of the feathers preserved in the two Yixian specimens appeared to Xu and colleagues, who described

12104-409: The outermost primaries. It is unclear whether the upper arm carried tertiaries. Covert feathers are preserved covering the upper part of the wing feathers in some specimens, and some specimens have preserved the contour feathers of the body. Unlike some more advanced birds, Confuciusornis lacked an alula , or "bastard wing". In modern birds this is formed by feathers anchored to the first digit of

12240-401: The outline of an upwards curving beak which sharply tapers towards its tip, while a C. sanctus specimen (IVPP V12352) has an upper margin that is almost straight, and a tip that appears to be slightly hooked downwards. Two further specimens (STM13-133 and STM13-162) belonging to an indeterminate species were described in 2020; the former suggests that, unlike modern birds, the beak on both jaws

12376-468: The oviraptorosaur specimen. However, the sequential moulting of modern birds is because the birds need to retain their ability to fly during the moult (except in penguins ). For lineages more primitive than the advent of flight, like oviraptorosaurs, this would not have been an issue, and all the wing and tail feathers of primitive feathered theropods may have moulted simultaneously, more like penguins than flying birds. However, Xu et al. (2010) rebutted that

12512-406: The path of obstructing branches. Peters sees Confuciusornis as capable of flapping flight but specialised in soaring flight. Also a controversy is the strength of the feathers. In 2010, Robert Nudds and Gareth Dyke published a study arguing that in both Confuciusornis and Archaeopteryx , the raches (central shafts) of the primary feathers were too thin and weak to have remained rigid during

12648-433: The pattern might reflect sexual dimorphism , with the streamer-like feathers only present in one sex (likely the males) which used them in courtship displays. This interpretation was followed by the majority of subsequent studies. Chiappe and colleagues, in 1999, argued that sexual dimorphism is not the only but the most reasonable explanation, noting that in modern birds the length of ornamental feathers often varies between

12784-412: The phylogenetic analysis of a 2014 study on the group Paraves and its relatives. In the unweight cladogram , Incisivosaurus was rendered as the sister taxon to Protarchaeopteryx , with their group being the most primitive oviraptorosaurians. In both weighted analyses however, Protarchaeopteryx was found to be the most primitive oviraptorosaurian, with Incisivosaurus as the next most basal . One of

12920-399: The plumage got periodically renewed. As in modern birds, molting individuals may have been present alongside non-molting individuals, and males and females may have molted at different times during the year, possibly explaining the co-occurrence of specimens with and without long tail feathers. Peters and Petters, on the other hand, suggested that Confuciusornis may have shed the feathers as

13056-410: The power stroke required for true flight. They argued that Confuciusornis would at most have employed gliding flight , which is also consistent with the unusual adaptations seen in its upper arm bones, and more likely used its wings for mere parachuting, limiting fall speed if it dropped from a tree. Gregory S. Paul , however, disagreed with their study. He argued that Nudds and Dyke had overestimated

13192-541: The provisions of the ICZN Code, e.g., incorrect original or subsequent spellings, names published only in a thesis, and generic names published after 1930 with no type species indicated. According to "Glossary" section of the zoological Code, suppressed names (per published "Opinions" of the International Commission of Zoological Nomenclature) remain available but cannot be used as the valid name for

13328-480: The purported moulting evidence is problematic due to the complete absence of previous-generation feathers, and suggested that the feather is too large to be considered as a "pin feather". Other authors agreed with the reply by Xu et al. (2010) that the structures do not represent the "pin feather", though they considered that the specimen might represent a mid to late immature stage. Incisivosaurus , as well as its potential synonym Protarchaeopteryx , were included in

13464-445: The rarity of individuals with an intermediate size was caused by Confuciusornis experiencing a growth spurt just prior to reaching adulthood, the shortness of which would have prevented many becoming fossilized during this phase. This initially slow growth followed by a growth spurt would have resulted in a S-shaped growth curve , similar to that inferred for non-avian dinosaurs. Such an extended dinosaurian mode of growth conflicts with

13600-568: The rest of the body, indicating that their absence is not simply due to poor preservation. Larry Martin and colleagues stated in 1998 that long tail feathers are present in about 5 to 10% of the specimens known at the time. A 2011 analysis by Jesús Marugán-Lobón and colleagues found that out of 130 specimens, 18% had long tail feathers and 28% had not, while in the remaining 54% preservation was insufficient to determine their presence or absence. The biological meaning of this pattern has been discussed controversially. Martin and colleagues suggested that

13736-470: The same kind as other (analogous) genera. The term "genus" comes from Latin genus , a noun form cognate with gignere ('to bear; to give birth to'). The Swedish taxonomist Carl Linnaeus popularized its use in his 1753 Species Plantarum , but the French botanist Joseph Pitton de Tournefort (1656–1708) is considered "the founder of the modern concept of genera". The scientific name (or

13872-402: The same would have been true for Archaeopteryx . The wrist of Confuciusornis shows fusion, forming a carpometacarpus . The second and third metacarpals were also partially fused, but the first was unfused, and the fingers could freely move relative to each other. The second metacarpal, which supported the flight feathers, was very heavily built; its finger carries a small claw. The claw of

14008-408: The scientific epithet) of a genus is also called the generic name ; in modern style guides and science, it is always capitalised. It plays a fundamental role in binomial nomenclature , the system of naming organisms , where it is combined with the scientific name of a species : see Botanical name and Specific name (zoology) . The rules for the scientific names of organisms are laid down in

14144-426: The sexes. Controversy arose from the observation that the known specimens of Confuciusornis can be divided into a small-sized and a large-sized group, but that this bimodal distribution is unrelated to the possession of long tail feathers. Chiappe and colleagues argued in 2008 that this size distribution can be explained by a dinosaur-like mode of growth (see section Growth ), and maintained that sexual dimorphism

14280-410: The shoulder joint was sideways, instead of angled upward as in modern birds; this means that Confuciusornis was unable to lift its wings high above its back. According to a study by Phil Senter in 2006, the joint was even pointed largely downwards meaning that the humerus could not be lifted above the horizontal. This would make Confuciusornis incapable of the upstroke required for flapping flight ;

14416-453: The side. Their articulation processes were rather long. The last of these vertebrae had a rectangular profile. Its neural arch had short processes pointing obliquely to above and sideways. The tail ended in a pygostyle, a complete fusion of the last vertebrae. Their number is uncertain. The pygostyle was about 40% longer than the first part of the tail. At its underside the pygostyle bore a well-developed keel, running from front to rear. Its top

14552-407: The simple splenial of Archaeopteryx ), and its lower margin followed the lower margin of the mandible. There was a large rostral mandibular fenestra and a small, rounded caudal fenestra behind it. Though only five specimens preserve parts of the beak's keratinous covering, these show that there would have been differences between species not seen in the skeleton. The holotype of C. dui preserves

14688-402: The skull roof much farther behind in modern birds, making the frontal bone of Confuciusornis small compared to those of modern birds. A prominent supraorbital flange formed the upper border of the orbit, and continued as the postorbital process, which had prominent crests which projected outwards to the sides, forming an expansion of the orbit's rim. The squamosal bone was fully incorporated into

14824-417: The skull) in the late 1990s, but in 2018, Elzanowski and colleagues concluded that the configuration seen in the temporal region of confuciusornithids was autapomorphic (a unique trait that evolved secondarily rather than having been retained from a primitive condition) for their group. The quadrate bone and the back end of the jugal bar were bound in a complex scaffolding that connected the squamosal bone with

14960-432: The spaces between the vertebral body and the neural arch . Their spinal processes were tall and narrow in side view. Their side processes projected horizontally and were deeply excavated at the rear underside. The sides of the back vertebrae also had deep oval excavations. Seven sacral vertebrae were fused into a synsacrum . The front sacral vertebra had a round and concave front articulation facet. The vertebral bodies of

15096-497: The specific name particular to the wolf. A botanical example would be Hibiscus arnottianus , a particular species of the genus Hibiscus native to Hawaii. The specific name is written in lower-case and may be followed by subspecies names in zoology or a variety of infraspecific names in botany . When the generic name is already known from context, it may be shortened to its initial letter, for example, C. lupus in place of Canis lupus . Where species are further subdivided,

15232-412: The standard format for a species name comprises the generic name, indicating the genus to which the species belongs, followed by the specific epithet, which (within that genus) is unique to the species. For example, the gray wolf 's scientific name is Canis lupus , with Canis ( Latin for 'dog') being the generic name shared by the wolf's close relatives and lupus (Latin for 'wolf') being

15368-403: The taxon is termed a synonym ; some authors also include unavailable names in lists of synonyms as well as available names, such as misspellings, names previously published without fulfilling all of the requirements of the relevant nomenclatural code, and rejected or suppressed names. A particular genus name may have zero to many synonyms, the latter case generally if the genus has been known for

15504-431: The tip of the snout. The borders of the nostrils were formed by the premaxillae above, the maxilla below, and the nasal wall at the back. Few specimens preserve the sutures of the braincase, but one specimen shows that the frontoparietal suture crossed the skull just behind the postorbital process and the hindmost wall of the orbit. This was similar to Archaeopteryx and Enaliornis , whereas it curves back and crosses

15640-421: The toes suggest that they were used for both walking and perching, while the large claws of the thumb and third finger were probably used for climbing. The wing feathers of Confuciusornis were long and modern in appearance. The primary wing feathers of a 0.5-kilogram individual reached 20.7 centimetres in length. The five longest primary feathers ( remiges primarii ) were more than 3 + 1 ⁄ 2 times

15776-433: The two feathered specimens, to change with age. The youngest specimen had relatively short primary feathers (those anchored to the hand) compared to its tail feathers. In the older specimen, the primary feathers were the same length as the tail feathers, and secondary feathers (those anchored to the lower arm) were also present. The primary feathers may have grown more slowly than the tail feathers, not reaching equal size until

15912-566: The underside. The next, the axis, had an expanded spinal process on the top and its side was excavated by an elongated groove in the side. The remaining neck vertebrae all had rather low spinal processes. There is no clear evidence of a pneumatisation, in the form of internal air spaces, of the vertebral bodies of the neck. The front articulation facets of the neck vertebrae were saddle-shaped. Their undersides were pinched. There were at least twelve back vertebrae. They were amphiplatian, flat at both ends, and had rather small intervertebral foramina ,

16048-576: The values quoted are the mean of "accepted" names alone (all "uncertain" names treated as unaccepted) and "accepted + uncertain" names (all "uncertain" names treated as accepted), with the associated range of uncertainty indicating these two extremes. Within Animalia, the largest phylum is Arthropoda , with 151,697 ± 33,160 accepted genus names, of which 114,387 ± 27,654 are insects (class Insecta). Within Plantae, Tracheophyta (vascular plants) make up

16184-429: The virus species " Salmonid herpesvirus 1 ", " Salmonid herpesvirus 2 " and " Salmonid herpesvirus 3 " are all within the genus Salmonivirus ; however, the genus to which the species with the formal names " Everglades virus " and " Ross River virus " are assigned is Alphavirus . As with scientific names at other ranks, in all groups other than viruses, names of genera may be cited with their authorities, typically in

16320-440: The weighted cladograms, using TNT, is shown below. Protarchaeopteryx Incisivosaurus Similicaudipteryx Avimimus Microvenator Caudipteryx Chirostenotes Gigantoraptor Oviraptor Citipati Khaan A 2022 study of the bite force of Incisivosaurus and comparisons with other oviraptorosaurs such as Citipati , Khaan , and Conchoraptor suggests that Incisivosaurus had

16456-398: The weights of these early birds, and that more accurate weight estimates allowed powered flight even with relatively narrow raches. Nudds and Dyke assumed a weight of 500 grams (18 oz) for Confuciusornis , as heavy as the modern teal . Paul argued that a more reasonable body weight estimate is about 180 grams (6.3 oz), less than that of a pigeon. Paul also noted that Confuciusornis

16592-503: The wings of Confuciusornis would have been white or, possibly, colored with carotenoid pigments. The long tail feathers of male specimens would have also been dark in color along their entire length. A 2018 study of the specimen CUGB P1401 indicated the presence of heavy spotting on the wings, throat, and crest of Confuciusornis . Hou assigned Confuciusornis to the Confuciusornithidae in 1995. At first he assumed it

16728-537: The younger Jiufotang Formation , which was considered to be of Early Cretaceous age. Later, both formations have been dated to the Lower Cretaceous ( Barremian to Aptian stages, 131–120 million years ago). In 1995, local farmers began digging for fossils near the village of Sihetun, Beipiao, in what would become one of the most productive localities of the Jehol biota. Large-scale professional excavations at this single locality have been carried out by

16864-542: Was a member of the Enantiornithes and the sister taxon of Gobipteryx . Later he understood that Confuciusornis was not an enantiornithean but concluded it was the sister taxon of the Enantiornithes, within a larger Sauriurae . This was heavily criticised by Chiappe who regarded Sauriurae to be paraphyletic as there were insufficient shared traits that indicated that the Confuciusornithidae and

17000-521: Was a primitive member of the group, and several features of the skull even support a relationship with the therizinosaurs , another theropod group that was probably herbivorous. In 2009 the holotype skull was scanned and analyzed in three dimensions. The results indicated that Incisivosaurus had less bird - like air spaces in the skull bones than later oviraptorosaurs did. It also found that Incisivosaurus had reduced olfactory lobes and expanded optic lobes similar to ornithomimosaurs . It suggested that

17136-443: Was a simple curved bar lacking a pointed process at the back, a hypocleidium . The sternum was relatively broad and had a low keel which was raised at the back end. This bony keel may or may not have anchored a larger, cartilaginous, keel for enlarged pectoral muscles . The scapulae (shoulder blades) were fused to the strut-like coracoid bones and may have formed a solid base for the attachment of wing muscles. The orientation of

17272-459: Was incised by a long groove between prominent ridges. Confuciusornis had an exceptionally large humerus (upper arm bone). Near its shoulder-end this was equipped with a prominent deltopectoral crest. Characteristically this crista deltopectoralis was with Confuciusornis pierced by an oval hole which may have reduced the bone's weight or enlarged the attachment area of the flight muscles. The furcula or wishbone, like that of Archaeopteryx ,

17408-595: Was large, likely relatively thick, and extended from the shoulder to the wrist, as in modern birds; the extent of the postpatagium is also similar to modern birds. Reticulate scales covered the underside of the foot, and the phalanges and metatarsals supported large, fleshy pads, although the interphalangeal pads were either small or entirely absent. In early 2010, a group of scientists led by Zhang Fucheng examined fossils with preserved melanosomes ( organelles which contain colors). By studying such fossils with an electron microscope , they found melanosomes preserved in

17544-413: Was made up of two separate elements that met at the midline, with feathers growing between them on the upper jaw. Also unlike modern birds, these specimens suggest that the upper beak extended backwards onto the maxilla due to the presence of foramina. The various specimens seem to have a variable number of neck vertebrae, some showing eight, others nine. The first vertebra, the atlas, bore a faint keel on

17680-402: Was no correlation between size and the possession of the long tail feathers. From this it was concluded that either the sexes did not differ in size or both sexes had the long feathers. The first case was deemed most likely which left the size distribution to be explained. It was hypothesized that the smaller animals consisted of very young individuals, that the large animals were adults and that

17816-399: Was not possible for non-avian dinosaurs and Mesozoic birds, including Confuciusornis , as these animals would have been too heavy in relation to the size of their eggs. Kaiser, in 2007, argued that Confuciusornis likely did not brood in an open nest but might have used crevices in trees for protection, and that the small size of the only known egg indicates large clutch sizes. In contrast,

17952-431: Was rather robust, with deep jaws, especially the mandible. The tomial crest of the upper jaw (a bony support for the jaw's cutting edge) was straight for its entire length. The premaxillae (front bones of the upper jaw) were fused together for most of the front half of the snout, but were separated at the tip by a V-shaped notch. The frontal processes that projected hindwards from the premaxillae were thin and extended above

18088-411: Was robust, especially at the front third of its length. The tomial crest was straight for its entire length, and a notch indented the sharp tip of the mandible. The mandible was spear-shaped in side view, due to its lower margin slanting downwards and back from its tip for the front third of its length (the jaw was also deepest at a point one third from the tip). The symphyseal part (where the two halves of

18224-433: Was similar to the modern pheasant-tailed jacana ( Hydrophasianus chirurgus ), a water-bird in which and the female is largest and adult individuals of both sexes have long tails, but only during the breeding season. Confuciusornis differs from the jacanas in that long tail feathers are present in specimens of all sizes, even in some of the smallest known specimens. This suggests that the long tail feathers might not have had

18360-420: Was straight; the tibia only slightly longer. The metatarsals of the foot were relatively short and fused to each other and to the lower ankle bones, forming a tarsometatarsus . A rudimentary fifth metatarsal is present. The first metatarsal was attached to the lower shaft of the second and supported a first toe or hallux , pointing to the back. The formula of the toe phalanges was 2-3-4-5-0. The proportions of

18496-617: Was unlike that of a modern ectothermic alligator but similar to the feathered non-avian dinosaur Beipiaosaurus . However, these authors assumed that endothermy in Confuciusornis had evolved independently from that seen in modern birds. This concurred with earlier work by Anusuya Chinsamy and colleagues, who described distinct lines of arrested growth and low vascularity in other Mesozoic birds that are more derived than Confuciusornis . Both features indicate slow growth, which, according to Chinsamy and colleagues, suggests low metabolic rates. Full endothermy, therefore, would have evolved late on

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