Confuciusornis
Encyclopedia
Confuciusornis is a genus of primitive crow-sized bird
s from the Early Cretaceous
Yixian
and Jiufotang Formation
s of China
, dating from 125 to 120 million years ago. Like modern birds, Confuciusornis had a toothless beak, but close 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 is the oldest known bird to have a beak. It was named after the Chinese moral philosopher Confucius
(551–479 BCE). Confuciusornis is one of the most abundant vertebrates found in the Yixian Formation, and several hundred complete, articulated specimens have been found.
at Beijing
, were presented a bird fossil bought at a flea market in Sihetun by amateur paleontologist Zhang He
. It showed a partial skeleton of a bird new to science of which even some feather remains had been preserved. In December 1993 two further specimens were acquired from a farmer, Yang Yushan. Soon afterwards, it was discovered that local farmers were in the process of collecting hundreds of specimens that were provisionally prepared by them to be illegally sold to commercial fossil dealers. Many hundreds have since also been added to the official collections of Chinese institutions. In 2010 the Shandong Tianyu Museum of Nature alone possessed 536 specimens. The fossils are compressed but otherwise typically very complete often showing the entire feathering of the animal.
Based on the abundant material, six species have been formally named and described: C. sanctus (the type species
), C. dui, C. feducciai, C. jianchangensis, C. chuonzhous and C. suniae. The latter two are usually considered synonymous with C. sanctus. Most species lived in the early Aptian
125 million year old Jianshangou Beds of the Yixian Formation
, though C. jianchangnsis is found in the later (120Ma) middle Aptian Jiufotang Formation
. C. sanctus is known from the former, and is one of the most common vertebrate species found in the Yixian, often present in dense concentrations. At one time forty were discovered on a surface of about 100 m². 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.
In 1995 Zhou, Hou, Zhang and Gu Youcai named Confuciusornis sanctus. The generic name combines the philosopher Confucius with a Greek ὄρνις, (ornis), "bird". The specific name means "holy one" in Latin
and is a translation of Chinese 圣贤, shèngxián, "sage", again in reference to Confucius. The holotype
specimen is IVPP V10918. In 1997 Hou named two species. The first was Confuciusornis chuonzhous, based on specimen IVPP V10919, originally a paratype
of C. sanctus. The specific name refers to Chuanzhou, an ancient name for Beipiao
. The second species was Confuciusornis suniae, based on specimen IVPP V11308. The specific name honours madam Sun, the wife of Shikuan Liang who donated the fossil to the IVPP. In 1999 Hou, Zhou, Zhang, Larry Martin
and Alan Feduccia
named Confuciusornis dui, based on specimen IVPP V11553. The specific name again honours a donating collector: Du Wengya. In 2009 Zhang Fucheng et al. named Confuciusornis feducciai, based on specimen D2454, the specific name honouring Feduccia. In 2010 Li Li
, Wang Jingqi and Hou Shilin named Confuciusornis jianchangensis, based on specimen PMOL-AB00114 found at Toudaoyingzi.
In 2002 Hou named the genus Jinzhouornis
. Luis Chiappe later concluded that this is probably a junior synonym of Confuciusornis.
Confuciusornis was about the size of a modern pigeon, with a wingspan of up to 0.7 meters (2.3 ft), and its body weight has been estimated to have been as much as 1.5 kilograms, or less than 0.2 kilograms. 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 a pygostyle
(a bone formed from a series of short, fused tail vertebrae) and a bony sternum
, 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 the jaw bones for small degenerated teeth.
The skull of Confuciusornis was equipped with a pointed toothless beak. It was relatively heavy-built and immobile, incapable of the kinesis
of modern birds that can raise the snout relative to the back of the skull. This immobility was caused by the presence of a triradiate postorbital
separating the eye-socket from the lower temporal opening, like with more basal theropods, and the premaxilla
e of the snout reaching all the way to the frontal
s, forcing the nasals
to the sides of the snout.
Fossils of Confuciusornis show that it 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 miscles. The furcula
or wishbone, like that of Archaeopteryx
, was a simple curved bar lacking a pointed process at the back, a hypocleidum. The sternum (breastbone) 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 scapula
e (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 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
; 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, however, and also the fingers could freely move relative to each other. The second metacarpal, supporting the flight feathers, was very heavily built; its finger carries a small claw. The claw of the first finger to the contrary was very large and curved, that of the third intermediate in size. 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
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 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.
, or "bastard wing". In modern birds this is formed by feathers anchored to the first digit of 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 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 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.
s with preserved melanosomes (organelle
s which contain colors). By studying such fossils with an electron microscope
, they found melanosomes preserved in a fossil Confuciusornis specimen, IVPP V13171. The melanosomes where of two types, eumelanosomes and pheomelanosomes. This indicates 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.
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, a strut-like coracoid, a large deltopectoral crest, a strong ulna
and an enlarged second metacarpal.
However, over the years several claims have been made that the flight of Confuciusornis suffered from more or less severe limitations.
The first of these regarded problems to attain a steep flight path due to a limited wing amplitude. In the interpretation of Senter (2006) of the position of the shoulder joint, a normal upstroke would be impossible precluding flapping flight entirely. Less radical 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 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 the path of obstructing branches. Peters sees Confuciusornis as capable of flapping flight but specialised in soaring flight.
A second problem 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 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 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 1.5 kilograms for Confuciusornis, as heavy as the modern teal
. Paul argued that a more reasonable body weight estimate is about 180 grams, less than that of a pigeon. Paul also noted that Confuciusornis 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 Chinese researchers questioned the correctness of the rachis measurements, stating that the specimens they had studied showed a shaft thickness of 2.1 to 2.3 millimetres as compared to the 1.2 millimetre reported by Nudds and Dyke. The latter 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 the Chinese fossil material with a differing rachis diameter.
, with one gender (likely the males) using the streamer-like feathers in courtship displays. However, while sexual variation is the most obvious explanation for the presence or absence of long tail feathers, other factors cannot be ruled out. For example, it is possible that some individuals lack tail feathers because they were fossilized during molting. 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.
Due to the large number of specimens, statistical analysis can be used to investigate this problem. In 2008 Chiappe et alii published a morphometrical
study of 106 fossils. The population showed a clear bimodal distribution
of the size of the animals with two weight classes. However, there 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 hypothesised that the smaller animals consisted of very young individuals, that the large animals were adults and that 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 fossilised during this phase. This interpretation was criticised by Dieter S. Peters who pointed out that, as the smaller animals were not neonates, the young of Confuciusornis had to grow very fast immediately after hatching regardless. This would then imply two growth spurts, which assumption was not very parsimonious. He thought the data would be more simply explained by assuming that both sexes had the long feathers and one of them was the largest. He favoured the possibility that these were the females, having observed such a pattern with the modern Pheasant-tailed Jacana
Hydrophasianus chirurgus, a water-bird in which both sexes have long tails and the female sex is the heaviest. He accounted for the fact that most specimens show no tails at all by the possibility that Confuciusornis shed the feathers as a defence mechanism, a method used by several extant species, which would have been triggered by the stress induced by the very volcanic explosion that buried the animals.
The growth speed relevant to this question can be independently measured by researching the bone structure. In 1998 Zhang determined that growth was fast, leading to fibrolamellar bone. Comparison with the bone structure of an alligator
indicated that Confuciusornis had a high metabolism comparable to that of modern birds. The growth speed of Confuciusornis would have been similar to that of Beipiaosaurus
. A study by Armand de Ricqlès in 2003 indicated that growth was essentially modern, Confuciusornis reaching its maximum size in at most twenty weeks, perhaps as few as thirteen. Basal birds would have limited their size, not by slowing growth but by limiting the period of growth.
s.
It has been hypothesized that Confuciusornis fed on plant materials due to its toothless beak, but no gastrolith
s or stomach contents had been reported (Zhou & Zhang, 2003). Dalsätt and colleagues (2006) described a specimen, IVPP
V13313 found in the Jiufotang Beds, that preserves seven to nine vertebrae and several ribs of a small fish, probably Jinanichthys
. These fish bones are formed into a tight cluster about six millimeters across, and the cluster is in contact with the seventh and eighth cervical vertebrae
of the bird. In this position it was likely in the crop of the bird, which may have been preparing to regurgitate a pellet
when it died. No other fish remains are present in the slab. (Dalsätt et al., 2006). Andrzej Elzanowski
already in 2002 had predicted that Confuciusornis was a predator. Dieter S. Peters has hypothesized that, although no remains of toe webs have been conserved, it caught its prey swimming using its rather soft bill to search for prey below the waterline. Andrei Zinoviev assumed it caught fish on the wing.
Several extant bird species have been presented as modern analogues of Confuciusornis providing insight into its possible lifestyle. Dieter S. Peters thought that it could be best compared with the White-tailed Tropicbird
Phaeton lepturus, a fisher that too has a long tail and narrow wings — and even often nests in the neighbourhood of volcanoes. The paradise kingfisher
s (genus Tanysiptera) of modern Australia
and New Guinea
have elongated "racket plumes" as their central tail feathers, giving them a superficial resemblance to Confuciusornis. These kingfishers also take fish as prey, but they are not specialized fishers. They take many insects and other small prey from their forest habitat.
s supporting the eyes of Confuciusornis and modern birds and other reptiles indicate that it may have been diurnal, similar to most modern birds.
in 1995. At first he assumed it was a member of the Enantiornithes
and the sister taxon of Gobipteryx
. Later he understood that Confuciusornis was not a enantiornith 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 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 illustrate its position in the tree of life; it has 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 (Mayr et al., 2005).
The present standard interpretation of the phylogenetic position of Confuciusornis can be shown in this cladogram
:
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 the enantiornithine Shanweiniao
.
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
s from the Early Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
Yixian
Yixian Formation
The Yixian Formation is a geological formation in Jinzhou, Liaoning, People's Republic of China, that spans 11 million years during the early Cretaceous period...
and Jiufotang Formation
Jiufotang Formation
The Jiufotang Formation is an Early Cretaceous geological formation in Chaoyang, Liaoning which has yielded fossils of feathered dinosaurs, primitive birds, pterosaurs, and other organisms. . It is a member of the Jehol group. The exact age of the Jiufotang has been debated for years, with...
s of China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
, dating from 125 to 120 million years ago. Like modern birds, Confuciusornis had a toothless beak, but close relatives of modern birds such as Hesperornis
Hesperornis
Hesperornis is a genus of flightless aquatic birds that spanned the first half of the Campanian age of the Late Cretaceous period . One of the lesser-known discoveries of the paleontologist O. C. Marsh in the late 19th century Bone Wars, it was an important early find in the history of avian...
and Ichthyornis
Ichthyornis
Ichthyornis is a genus of toothed seabirds from the Late Cretaceous of North America. Its fossil remains are known from the chalks of Alberta, Alabama, Kansas, New Mexico, Saskatchewan, and Texas, in strata that were laid down in the Western Interior Seaway during the Turonian-Campanian ages,...
were toothed, indicating that the loss of teeth occurred convergently in Confuciusornis and living birds. It is the oldest known bird to have a beak. It was named after the Chinese moral philosopher Confucius
Confucius
Confucius , literally "Master Kong", was a Chinese thinker and social philosopher of the Spring and Autumn Period....
(551–479 BCE). Confuciusornis is one of the most abundant vertebrates found in the Yixian Formation, and several hundred complete, articulated specimens have been found.
Discovery and naming
In November 1993 Chinese paleontologists Zhou Zhonge, Hu Yoaming and Hou Lianhai, of the Institute of Vertebrate Paleontology and PaleoanthropologyInstitute of Vertebrate Paleontology and Paleoanthropology
The Institute of Vertebrate Paleontology and Paleoanthropology of China is a prominent research institution and collections repository for fossils, including many dinosaur and pterosaurand cat poo specimens...
at Beijing
Beijing
Beijing , also known as Peking , is the capital of the People's Republic of China and one of the most populous cities in the world, with a population of 19,612,368 as of 2010. The city is the country's political, cultural, and educational center, and home to the headquarters for most of China's...
, were presented a bird fossil bought at a flea market in Sihetun by amateur paleontologist Zhang He
Zhang He
Zhang He was a military general serving under the warlord Cao Cao during the late Han Dynasty era of Chinese history. He continued serving the state of Cao Wei during the Three Kingdoms period until his death....
. It showed a partial skeleton of a bird new to science of which even some feather remains had been preserved. In December 1993 two further specimens were acquired from a farmer, Yang Yushan. Soon afterwards, it was discovered that local farmers were in the process of collecting hundreds of specimens that were provisionally prepared by them to be illegally sold to commercial fossil dealers. Many hundreds have since also been added to the official collections of Chinese institutions. In 2010 the Shandong Tianyu Museum of Nature alone possessed 536 specimens. The fossils are compressed but otherwise typically very complete often showing the entire feathering of the animal.
Based on the abundant material, six species have been formally named and described: C. sanctus (the type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
), C. dui, C. feducciai, C. jianchangensis, C. chuonzhous and C. suniae. The latter two are usually considered synonymous with C. sanctus. Most species lived in the early Aptian
Aptian
The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous epoch or series and encompasses the time from 125.0 ± 1.0 Ma to 112.0 ± 1.0 Ma , approximately...
125 million year old Jianshangou Beds of the Yixian Formation
Yixian Formation
The Yixian Formation is a geological formation in Jinzhou, Liaoning, People's Republic of China, that spans 11 million years during the early Cretaceous period...
, though C. jianchangnsis is found in the later (120Ma) middle Aptian Jiufotang Formation
Jiufotang Formation
The Jiufotang Formation is an Early Cretaceous geological formation in Chaoyang, Liaoning which has yielded fossils of feathered dinosaurs, primitive birds, pterosaurs, and other organisms. . It is a member of the Jehol group. The exact age of the Jiufotang has been debated for years, with...
. C. sanctus is known from the former, and is one of the most common vertebrate species found in the Yixian, often present in dense concentrations. At one time forty were discovered on a surface of about 100 m². 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
Tuff
Tuff is a type of rock consisting of consolidated volcanic ash ejected from vents during a volcanic eruption. Tuff is sometimes called tufa, particularly when used as construction material, although tufa also refers to a quite different rock. Rock that contains greater than 50% tuff is considered...
stone in which the fossils were found to be deposited as lake sediments.
In 1995 Zhou, Hou, Zhang and Gu Youcai named Confuciusornis sanctus. The generic name combines the philosopher Confucius with a Greek ὄρνις, (ornis), "bird". The specific name means "holy one" in Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
and is a translation of Chinese 圣贤, shèngxián, "sage", again in reference to Confucius. The holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
specimen is IVPP V10918. In 1997 Hou named two species. The first was Confuciusornis chuonzhous, based on specimen IVPP V10919, originally a paratype
Paratype
Paratype is a technical term used in the scientific naming of species and other taxa of organisms. The exact meaning of the term paratype when it is used in zoology is not the same as the meaning when it is used in botany...
of C. sanctus. The specific name refers to Chuanzhou, an ancient name for Beipiao
Beipiao
Beipiao is a city in Chaoyang prefecture, Liaoning province, in Northeast China. It has a population of 202,807. The main industry in the area is coal mining. With vertical shafts of almost 1000m, these are some of the deepest coal mines in China. The coal produced is used for coking...
. The second species was Confuciusornis suniae, based on specimen IVPP V11308. The specific name honours madam Sun, the wife of Shikuan Liang who donated the fossil to the IVPP. In 1999 Hou, Zhou, Zhang, Larry Martin
Larry Martin
Larry Martin is an American vertebrate paleontologist and curator of the Natural History Museum and Biodiversity Research Center at the University of Kansas. Among Martin's work is research on the Triassic reptile Longisquama and theropod dinosaur Caudipteryx...
and Alan Feduccia
Alan Feduccia
Alan Feduccia is a paleornithologist, specializing in the origins and phylogeny of birds. He is now Professor Emeritus at the University of North Carolina. Feduccia's principal authored works include two books, The Age of Birds and The Origin and Evolution of Birds, and numerous papers in various...
named Confuciusornis dui, based on specimen IVPP V11553. The specific name again honours a donating collector: Du Wengya. In 2009 Zhang Fucheng et al. named Confuciusornis feducciai, based on specimen D2454, the specific name honouring Feduccia. In 2010 Li Li
Li Li
Li Li may refer to:*Li Li , Chinese badminton player*Li Li , fictional character in the Water Margin*Muzi Mei , real name Li Li, Chinese blogger*Li Li , Chinese artistic gymnast...
, Wang Jingqi and Hou Shilin named Confuciusornis jianchangensis, based on specimen PMOL-AB00114 found at Toudaoyingzi.
In 2002 Hou named the genus Jinzhouornis
Jinzhouornis
Jinzhouornis is a dubious genus of prehistoric birds. Their fossils have found in rocks of the Yixian Formation of Liaoning Province , dating from the Early Cretaceous ....
. Luis Chiappe later concluded that this is probably a junior synonym of Confuciusornis.
Description
Confuciusornis shows a mix of basal and derived traits. It was more "advanced" or derived than Archaeopteryx in possessing a short tail with a pygostyle
Pygostyle
Pygostyle refers to a number of the final few caudal vertebrae fused into a single ossification, supporting the tail feathers and musculature. In modern birds, the rectrices attach to these....
(a bone formed from a series of short, fused tail vertebrae) and a bony sternum
Sternum
The sternum or breastbone is a long flat bony plate shaped like a capital "T" located anteriorly to the heart in the center of the thorax...
, 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 the jaw bones for small degenerated teeth.
The skull of Confuciusornis was equipped with a pointed toothless beak. It was relatively heavy-built and immobile, incapable of the kinesis
Kinesis
Kinesis, like a taxis, is a movement or activity of a cell or an organism in response to a stimulus. However, unlike taxis, the response to the stimulus provided is non-directional....
of modern birds that can raise the snout relative to the back of the skull. This immobility was caused by the presence of a triradiate postorbital
Postorbital
The postorbital is one of the bones in vertebrate skulls which forms a portion of the dermal skull roof and, sometimes, a ring about the orbit. Generally, it is located behind the postfrontal and posteriorly to the orbital fenestra. In some vertebrates, the postorbital is fused with the postfrontal...
separating the eye-socket from the lower temporal opening, like with more basal theropods, and the premaxilla
Premaxilla
The incisive bone is the portion of the maxilla adjacent to the incisors. It is a pair of small cranial bones at the very tip of the jaws of many animals, usually bearing teeth, but not always. They are connected to the maxilla and the nasals....
e of the snout reaching all the way to the frontal
Frontal bone
The frontal bone is a bone in the human skull that resembles a cockleshell in form, and consists of two portions:* a vertical portion, the squama frontalis, corresponding with the region of the forehead....
s, forcing the nasals
Nasal bone
The nasal bones are two small oblong bones, varying in size and form in different individuals; they are placed side by side at the middle and upper part of the face, and form, by their junction, "the bridge" of the nose.Each has two surfaces and four borders....
to the sides of the snout.
Fossils of Confuciusornis show that it had an exceptionally large humerus
Humerus
The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow....
(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 miscles. The furcula
Furcula
The ' is a forked bone found in birds, formed by the fusion of the two clavicles. In birds, its function is the strengthening of the thoracic skeleton to withstand the rigors of flight....
or wishbone, like that of Archaeopteryx
Archaeopteryx
Archaeopteryx , sometimes referred to by its German name Urvogel , is a genus of theropod dinosaur that is closely related to birds. The name derives from the Ancient Greek meaning "ancient", and , meaning "feather" or "wing"...
, was a simple curved bar lacking a pointed process at the back, a hypocleidum. The sternum (breastbone) was relatively broad and had a low keel
Keel (bird)
A keel or carina in bird anatomy is an extension of the sternum which runs axially along the midline of the sternum and extends outward, perpendicular to the plane of the ribs. The keel provides an anchor to which a bird's wing muscles attach, thereby providing adequate leverage for flight...
which was raised at the back end. This bony keel may or may not have anchored a larger, cartilaginous, keel for enlarged pectoral
Pectoral
Pectoral may refer to:* Pectoral cross, a cross worn on the chest* a decorative, usually jeweled version of a gorget* Pectoral , often iconographic with hieroglyphs* Pectoralis major muscle, commonly referred to as "pectorals" or "pecs"...
muscles. The scapula
Scapula
In anatomy, the scapula , omo, or shoulder blade, is the bone that connects the humerus with the clavicle ....
e (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 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
Bird flight
Flight is the main mode of locomotion used by most of the world's bird species. Flight assists birds while feeding, breeding and avoiding predators....
; the same would have been true for Archaeopteryx.
The wrist of Confuciusornis shows fusion, forming a carpometacarpus
Carpometacarpus
The carpometacarpus is the fusion of the carpal and metacarpal bone, essentially a single fused bone between the wrist and the knuckles. It is a smallish bone in most birds, generally flattened and with a large hole in the middle. In flightless birds, however, its shape may be slightly different,...
. The second and third metacarpals were also partially fused but the first was unfused, however, and also the fingers could freely move relative to each other. The second metacarpal, supporting the flight feathers, was very heavily built; its finger carries a small claw. The claw of the first finger to the contrary was very large and curved, that of the third intermediate in size. The formula of the finger phalanges was 2-3-4-0-0.
The pelvis
Pelvis
In human anatomy, the pelvis is the lower part of the trunk, between the abdomen and the lower limbs .The pelvis includes several structures:...
was connected to a sacrum
Sacrum
In vertebrate anatomy the sacrum is a large, triangular bone at the base of the spine and at the upper and back part of the pelvic cavity, where it is inserted like a wedge between the two hip bones. Its upper part connects with the last lumbar vertebra, and bottom part with the coccyx...
formed by seven sacral vertebrae. The pubis
Pubis
Pubis may refer to:* Pubis * Mons pubis, a padding of fat that protects the pubis bone...
was strongly pointing backwards. The left and right ischia were not fused. The femur
Femur
The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...
was straight; the tibia
Tibia
The tibia , shinbone, or shankbone is the larger and stronger of the two bones in the leg below the knee in vertebrates , and connects the knee with the ankle bones....
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
Tarsometatarsus
The tarsometatarsus is a bone that is found in the lower leg of certain tetrapods, namely birds.It is formed from the fusion of several bones found in other types of animals, and homologous to the mammalian tarsal and metatarsal bones...
. 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
Hallux
In tetrapods, the hallux is the innermost toe of the foot. Despite its name it may not be the longest toe on the foot of some individuals...
, pointing to the back. The formula of the toe phalanges was 2-3-4-5-0. The proportions of 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.
Feathers
The wing feathers of Confuciusornis were long and modern in appearance. The primary wing feathers of a 0.5 kilogram individual reached 20.7 centimeters in length. The five longest primary feathers (remiges primarii) were more than 3.5 times 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. Thus, the wing shape was very unlike that of living birds, being long and narrow. The primary feathers were asymmetrical to varying degree, and especially so in 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 alulaAlula
The alula, or bastard wing, is a small projection on the anterior edge of the wing of modern birds. The alula is the freely moving first digit, a bird's "thumb," and is typically covered with three to five small feathers, with the exact number depending on the species...
, or "bastard wing". In modern birds this is formed by feathers anchored to the first digit of 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 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 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
Sexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...
. 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.
Colouration
In early 2010, a group of scientists led by Zhang Fucheng examined fossilFossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
s with preserved melanosomes (organelle
Organelle
In cell biology, an organelle is a specialized subunit within a cell that has a specific function, and is usually separately enclosed within its own lipid bilayer....
s which contain colors). By studying such fossils with an electron microscope
Microscope
A microscope is an instrument used to see objects that are too small for the naked eye. The science of investigating small objects using such an instrument is called microscopy...
, they found melanosomes preserved in a fossil Confuciusornis specimen, IVPP V13171. The melanosomes where of two types, eumelanosomes and pheomelanosomes. This indicates that Confuciusornis had hues of grey
Grey
Grey or gray is an achromatic or neutral color.Complementary colors are defined to mix to grey, either additively or subtractively, and many color models place complements opposite each other in a color wheel. To produce grey in RGB displays, the R, G, and B primary light sources are combined in...
, red
Red
Red is any of a number of similar colors evoked by light consisting predominantly of the longest wavelengths of light discernible by the human eye, in the wavelength range of roughly 630–740 nm. Longer wavelengths than this are called infrared , and cannot be seen by the naked eye...
/brown
Brown
Brown is a color term, denoting a range of composite colors produced by a mixture of orange, red, rose, or yellow with black or gray. The term is from Old English brún, in origin for any dusky or dark shade of color....
and black
Black
Black is the color of objects that do not emit or reflect light in any part of the visible spectrum; they absorb all such frequencies of light...
, possibly something like the modern zebra finch
Zebra Finch
The Zebra Finch, Taeniopygia guttata, is the most common and familiar estrildid finch of Central Australia and ranges over most of the continent, avoiding only the cool moist south and the tropical far north. It also can be found natively in Indonesia and East Timor...
. It was also the first time an early bird fossil has been shown to contain preserved pheomelanosomes.
Flight
Ulna
The ulna is one of the two long bones in the forearm, the other being the radius. It is prismatic in form and runs parallel to the radius, which is shorter and smaller. In anatomical position The ulna is one of the two long bones in the forearm, the other being the radius. It is prismatic in form...
and an enlarged second metacarpal.
However, over the years several claims have been made that the flight of Confuciusornis suffered from more or less severe limitations.
The first of these regarded problems to attain a steep flight path due to a limited wing amplitude. In the interpretation of Senter (2006) of the position of the shoulder joint, a normal upstroke would be impossible precluding flapping flight entirely. Less radical is the assessment that due to the lack of a keeled sternum and a high acrocoracoid, the Musculus pectoralis minor
Pectoralis minor muscle
The pectoralis minor is a thin, triangular muscle, situated at the upper part of the chest, beneath the pectoralis major.-Origin and insertion:...
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 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 the path of obstructing branches. Peters sees Confuciusornis as capable of flapping flight but specialised in soaring flight.
A second problem is the strength of the feathers. In 2010 Robert Nudds and Gareth Dyke published a study arguing that in both Confuciusornis and Archaeopteryx
Archaeopteryx
Archaeopteryx , sometimes referred to by its German name Urvogel , is a genus of theropod dinosaur that is closely related to birds. The name derives from the Ancient Greek meaning "ancient", and , meaning "feather" or "wing"...
, the raches (central shafts) of the primary feathers were too thin and weak to have remained rigid during 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
Gregory S. Paul
Gregory Scott Paul is a freelance researcher, author and illustrator who works in paleontology, and more recently has examined sociology and theology. He is best known for his work and research on theropod dinosaurs and his detailed illustrations, both live and skeletal...
, however, disagreed with their study. He argued that Nudds and Dyke had overestimated 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 1.5 kilograms for Confuciusornis, as heavy as the modern teal
Common Teal
The Eurasian Teal or Common Teal is a common and widespread duck which breeds in temperate Eurasia and migrates south in winter. The Eurasian Teal is often called simply the Teal due to being the only one of these small dabbling ducks in much of its range...
. Paul argued that a more reasonable body weight estimate is about 180 grams, less than that of a pigeon. Paul also noted that Confuciusornis 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 Chinese researchers questioned the correctness of the rachis measurements, stating that the specimens they had studied showed a shaft thickness of 2.1 to 2.3 millimetres as compared to the 1.2 millimetre reported by Nudds and Dyke. The latter 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 the Chinese fossil material with a differing rachis diameter.
Sexual variation
Many specimens of Confuciusornis preserve a single pair of long, streamer-like tail feathers. However, most do not, even specimens which otherwise have exquisitely preserved feathers on the rest of the body; their predominance has been estimated to be as high as 90-95%. This difference has been suggested to indicate sexual dimorphismSexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...
, with one gender (likely the males) using the streamer-like feathers in courtship displays. However, while sexual variation is the most obvious explanation for the presence or absence of long tail feathers, other factors cannot be ruled out. For example, it is possible that some individuals lack tail feathers because they were fossilized during molting. 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.
Due to the large number of specimens, statistical analysis can be used to investigate this problem. In 2008 Chiappe et alii published a morphometrical
Morphometrics
Morphometrics refers to the quantitative analysis of form, a concept that encompasses size and shape. Morphometric analyses are commonly performed on organisms, and are useful in analyzing their fossil record, the impact of mutations on shape, developmental changes in form, covariances between...
study of 106 fossils. The population showed a clear bimodal distribution
Bimodal distribution
In statistics, a bimodal distribution is a continuous probability distribution with two different modes. These appear as distinct peaks in the probability density function, as shown in Figure 1....
of the size of the animals with two weight classes. However, there was no correlation
Correlation
In statistics, dependence refers to any statistical relationship between two random variables or two sets of data. Correlation refers to any of a broad class of statistical relationships involving dependence....
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 hypothesised that the smaller animals consisted of very young individuals, that the large animals were adults and that 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 fossilised during this phase. This interpretation was criticised by Dieter S. Peters who pointed out that, as the smaller animals were not neonates, the young of Confuciusornis had to grow very fast immediately after hatching regardless. This would then imply two growth spurts, which assumption was not very parsimonious. He thought the data would be more simply explained by assuming that both sexes had the long feathers and one of them was the largest. He favoured the possibility that these were the females, having observed such a pattern with the modern Pheasant-tailed Jacana
Pheasant-tailed Jacana
The Pheasant-tailed Jacana is a jacana in the monotypic genus Hydrophasianus. Jacanas are a group of waders in the family Jacanidae that are identifiable by their huge feet and claws which enable them to walk on floating vegetation in shallow lakes, their preferred habitat...
Hydrophasianus chirurgus, a water-bird in which both sexes have long tails and the female sex is the heaviest. He accounted for the fact that most specimens show no tails at all by the possibility that Confuciusornis shed the feathers as a defence mechanism, a method used by several extant species, which would have been triggered by the stress induced by the very volcanic explosion that buried the animals.
The growth speed relevant to this question can be independently measured by researching the bone structure. In 1998 Zhang determined that growth was fast, leading to fibrolamellar bone. Comparison with the bone structure of an alligator
Alligator
An alligator is a crocodilian in the genus Alligator of the family Alligatoridae. There are two extant alligator species: the American alligator and the Chinese alligator ....
indicated that Confuciusornis had a high metabolism comparable to that of modern birds. The growth speed of Confuciusornis would have been similar to that of Beipiaosaurus
Beipiaosaurus
Beipiaosaurus is a genus of therizinosauroid theropod dinosaur from the Early Cretaceous of China.The exact classification of therizinosaurs had in the past been hotly debated, since their prosauropod-like teeth and body structure indicate that they were generally herbivorous, unlike typical...
. A study by Armand de Ricqlès in 2003 indicated that growth was essentially modern, Confuciusornis reaching its maximum size in at most twenty weeks, perhaps as few as thirteen. Basal birds would have limited their size, not by slowing growth but by limiting the period of growth.
Diet
There are immature specimens known, and from the analysis of bone growth patterns of young adults it has been estimated that Confuciusornis reached maturity somewhat slower than extant small birds, but faster than advanced dinosaurs (de Ricqlès et al., 2003), which might indicate an omnivorous diet similar to modern crowCrow
Crows form the genus Corvus in the family Corvidae. Ranging in size from the relatively small pigeon-size jackdaws to the Common Raven of the Holarctic region and Thick-billed Raven of the highlands of Ethiopia, the 40 or so members of this genus occur on all temperate continents and several...
s.
It has been hypothesized that Confuciusornis fed on plant materials due to its toothless beak, but no gastrolith
Gastrolith
A gastrolith, also called a stomach stone or gizzard stones, is a rock held inside a gastrointestinal tract. Gastroliths are retained in the muscular gizzard and used to grind food in animals lacking suitable grinding teeth. The grain size depends upon the size of the animal and the gastrolith's...
s or stomach contents had been reported (Zhou & Zhang, 2003). Dalsätt and colleagues (2006) described a specimen, IVPP
Institute of Vertebrate Paleontology and Paleoanthropology
The Institute of Vertebrate Paleontology and Paleoanthropology of China is a prominent research institution and collections repository for fossils, including many dinosaur and pterosaurand cat poo specimens...
V13313 found in the Jiufotang Beds, that preserves seven to nine vertebrae and several ribs of a small fish, probably Jinanichthys
Jinanichthys
Jinanichthys is an extinct genus of osteoglossiform which existed in China during the early Cretaceous period. It contains the species Jinanichthys longicephalus....
. These fish bones are formed into a tight cluster about six millimeters across, and the cluster is in contact with the seventh and eighth cervical vertebrae
Cervical vertebrae
In vertebrates, cervical vertebrae are those vertebrae immediately inferior to the skull.Thoracic vertebrae in all mammalian species are defined as those vertebrae that also carry a pair of ribs, and lie caudal to the cervical vertebrae. Further caudally follow the lumbar vertebrae, which also...
of the bird. In this position it was likely in the crop of the bird, which may have been preparing to regurgitate a pellet
Pellet (ornithology)
A pellet, in ornithology, is the mass of undigested parts of a bird's food that some bird species occasionally regurgitate. The contents of a bird's pellet depend on its diet, but can include the exoskeletons of insects, indigestible plant matter, bones, fur, feathers, bills, claws, and teeth...
when it died. No other fish remains are present in the slab. (Dalsätt et al., 2006). Andrzej Elzanowski
Andrzej Elżanowski
Andrzej Elżanowski is a Polish paleontologist and vertebrate zoologist specializing in bird phylogeny. Together with Peter Wellnhofer he described a coelurosaur theropod Archaeornithoides in 1992...
already in 2002 had predicted that Confuciusornis was a predator. Dieter S. Peters has hypothesized that, although no remains of toe webs have been conserved, it caught its prey swimming using its rather soft bill to search for prey below the waterline. Andrei Zinoviev assumed it caught fish on the wing.
Several extant bird species have been presented as modern analogues of Confuciusornis providing insight into its possible lifestyle. Dieter S. Peters thought that it could be best compared with the White-tailed Tropicbird
White-tailed Tropicbird
The White-tailed Tropicbird Phaethon lepturus, is a tropicbird, smallest of three closely related seabirds of the tropical oceans and smallest member of the order Phaethontiformes. It occurs in the tropical Atlantic, western Pacific and Indian Oceans...
Phaeton lepturus, a fisher that too has a long tail and narrow wings — and even often nests in the neighbourhood of volcanoes. The paradise kingfisher
Paradise kingfisher
The Paradise kingfishers are a group of tree kingfishers found in Australasia. There are eight species:* Little Paradise Kingfisher, Tanysiptera hydrocharis* Common Paradise Kingfisher, Tanysiptera galatea...
s (genus Tanysiptera) of modern Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
and New Guinea
New Guinea
New Guinea is the world's second largest island, after Greenland, covering a land area of 786,000 km2. Located in the southwest Pacific Ocean, it lies geographically to the east of the Malay Archipelago, with which it is sometimes included as part of a greater Indo-Australian Archipelago...
have elongated "racket plumes" as their central tail feathers, giving them a superficial resemblance to Confuciusornis. These kingfishers also take fish as prey, but they are not specialized fishers. They take many insects and other small prey from their forest habitat.
Daily activity patterns
Comparisons between the scleral ringSclerotic ring
Sclerotic rings are rings of bone found in the eyes of several groups of vertebrate animals, except for mammals and crocodilians. They can be made up of single bones or small bones together. They are believed to have a role in supporting the eye, especially in animals whose eyes are not spherical,...
s supporting the eyes of Confuciusornis and modern birds and other reptiles indicate that it may have been diurnal, similar to most modern birds.
Classification
Hou assigned Confuciusornis to the ConfuciusornithidaeConfuciusornithidae
Confuciusornithidae is a family of primitive birds from the early Cretaceous Period of China. It consists of four genera. About half of all the confuciusornithid specimens, including reprersentatives of all species, that have preserved feathers possess a pair of distinctive ribbon-like tail...
in 1995. At first he assumed it was a member of the Enantiornithes
Enantiornithes
Enantiornithes is an extinct group of primitive birds. They were the most abundant and diverse avialans of the Mesozoic. Almost all retained teeth and clawed fingers on each wing, but otherwise looked much like modern birds externally. Over 50 species of Enantiornithines have been named, but some...
and the sister taxon of Gobipteryx
Gobipteryx
Gobipteryx is the name given to a genus of enantiornithine bird from the Late Cretaceous Period. Its fossils were found in the Barun Goyot Formation in the Gobi Desert, Mongolia and first described in 1976 from two fragmentary skulls...
. Later he understood that Confuciusornis was not a enantiornith but concluded it was the sister taxon of the Enantiornithes, within a larger Sauriurae
Sauriurae
Sauriurae is a now-deprecated subclass of birds created by Ernst Haeckel in 1866. It was intended to include Archaeopteryx and distinguish it from all other birds then known, which he grouped in the sister-group Ornithurae...
. This was heavily criticised by Chiappe who regarded Sauriurae to be paraphyletic as there were insufficient shared traits that indicated that the Confuciusornithidae and the Enantiornithes were closely related. In 2001 Ji Qiang suggested an alternative position as the sister taxon of the Ornithothoraces
Ornithothoraces
Ornithothoraces is a clade of birds which includes all enantiornithines and modern birds .The name Ornithothoraces means "bird thoraxes". This refers to a modern, highly derived, anatomy of the thorax which gave the ornithothoracines superior flight capability compared to more primitive birds...
.
In 2002 Ji's hypothesis was confirmed by a cladistic analysis by Chiappe, who defined a new group: the Pygostylia
Pygostylia
Pygostylia is a group of birds which includes Confuciusornis and all of the more derived birds; the Ornithothoraces. Chiappe defined the Pygostylia as "the common ancestor of the Confuciusornithidae and Neornithes plus all its descendants". This is a node-based definition.Chiappe united the...
of which Confuciusornis is by definition the most basal member. Several traits of Confuciusornis illustrate its position in the tree of life; it has a more "primitive" skull than Archaeopteryx
Archaeopteryx
Archaeopteryx , sometimes referred to by its German name Urvogel , is a genus of theropod dinosaur that is closely related to birds. The name derives from the Ancient Greek meaning "ancient", and , meaning "feather" or "wing"...
, but it is the first known bird to have lost the long tail of Archaeopteryx and develop fused tail vertebrae, a pygostyle
Pygostyle
Pygostyle refers to a number of the final few caudal vertebrae fused into a single ossification, supporting the tail feathers and musculature. In modern birds, the rectrices attach to these....
. One controversial study concluded that Confuciusornis may be more closely related to Microraptor
Microraptor
Microraptor is a genus of small, four-winged dromaeosaurid dinosaurs. Numerous well-preserved fossil specimens have been recovered from Liaoning, China...
and other dromaeosaurids
Dromaeosauridae
Dromaeosauridae is a family of bird-like theropod dinosaurs. They were small- to medium-sized feathered carnivores that flourished in the Cretaceous Period. The name Dromaeosauridae means 'running lizards', from Greek dromeus meaning 'runner' and sauros meaning 'lizard'...
than to Archaeopteryx, but this study was criticized on methodological grounds (Mayr et al., 2005).
The present standard interpretation of the phylogenetic position of Confuciusornis can be shown in this cladogram
Cladogram
A cladogram is a diagram used in cladistics which shows ancestral relations between organisms, to represent the evolutionary tree of life. Although traditionally such cladograms were generated largely on the basis of morphological characters, DNA and RNA sequencing data and computational...
:
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
Enantiornithes
Enantiornithes is an extinct group of primitive birds. They were the most abundant and diverse avialans of the Mesozoic. Almost all retained teeth and clawed fingers on each wing, but otherwise looked much like modern birds externally. Over 50 species of Enantiornithines have been named, but some...
birds. True, mobile tail fans only appeared in ornithuromorph birds, and possibly in the enantiornithine Shanweiniao
Shanweiniao
Shanweiniao is an extinct genus of long-beaked enantiornithine bird from Early Cretaceous China. One species is known, Shanweiniao cooperorum. There is one known fossil, a slab and counterslab. The fossil is in the collection of the Dalian Natural History Museum, and has accession number DNHM...
.
