Confuciusornis
Confuciusornis | |
---|---|
C. sanctus fossil preserving long wing and tail feathers, Natural History Museum, Vienna | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Clade: | Dinosauria |
Clade: | Saurischia |
Clade: | Theropoda |
Clade: | Avialae |
Family: | †Confuciusornithidae |
Genus: | †Confuciusornis Hou et al., 1995 |
Type species | |
†Confuciusornis sanctus Hou et al., 1995
| |
Other species | |
| |
Synonyms | |
Genus synonymy
Species synonymy (C. sanctus)
|
Confuciusornis is a
History of discovery
In November 1993, the Chinese paleontologists Hou Lianhai and Hu Yoaming of the
Together with the early mammal
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 the
At one time forty individuals 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.[16]
Additional species and synonyms
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 a species.[10]: 50 In the case of Confuciusornis, only C. sanctus is universally accepted.
- Confuciusornis chuonzhous was named by Hou in 1997 based on specimen IVPP V10919, originally a paratype of C. sanctus. The specific name refers to Chuanzhou, an ancient name for Beipiao.[17] C. chuonzhous is now generally considered synonymous with C. sanctus.[18]
- Confuciusornis suniae, named by Hou in the same 1997 publication, was based on specimen IVPP V11308. The specific name honours madam Sun, the wife of Shikuan Liang who donated the fossil to the IVPP.[17] C. suniae is now usually considered synonymous with C. sanctus.[18]
- Confuciusornis dui was named by Hou and colleagues in 1999. The specific name again honours the donating collector, Du Wengya. The holotype specimen (IVPP V11553) is a nearly complete skeleton of an adult that includes a pair of long tail feathers and the impression of the horny beak. A second specimen, the paratype IVPP 11521, is fragmentary and includes some vertebrae and ribs, tail, sternum and pelvis, and femora. According to Hou and colleagues, C. dui was smaller and more gracile than most other Confuciusornis specimens, with the holotype being ca. 15% smaller than the holotype of C. sanctus and ca. 30% smaller than larger individuals of that species. The jaw tips were more pointed than in C. sanctus, and the mandible lacked the underside keel that is distinct in the latter species. Further differences to the type species can be found in the postcranium: The claw on the first digit was not enlarged as in C. sanctus. The sternum was more elongate and differed in anatomical details, and the lower segment of the hind limb (the tarsometatarsus) was shorter than the pygostyle of the tail.[19] A statistical analysis by Marguán-Lobon and colleagues in 2011 revealed no significant differences to specimens referred to the smallest size class of C. sanctus, suggesting that the supposed differences are individual variations of a single species. However, these authors could not re-locate the C. dui holotype, which is possibly lost, and therefore had to rely on a cast of that specimen for their measurements. A re-study of the C. dui specimens would be required in order to evaluate the validity of the species.[20]
- Confuciusornis feducciai was named in 2009 by Zhang Fucheng and colleagues, the specific name honouring ornithologist Alan Feduccia. The holotype, D2454, was discovered at the Sihetun locality and is kept at the Dalian Natural Museum. According to Zhang and colleagues, C. feducciai differed from other Confuciusornis species in its larger size, skeletal proportions, and a number of morphological features. The forelimb was 15% longer than the hind limb, while they were of equal length in C. sanctus. The upper end of the humerus lacked the large opening (foramen) that is characteristic for other Confuciusornis specimens. The first phalanx of the first digit was more slender. Other differences occur in the furcula, which was V-shaped; the sternum, which was broader than long; and the ischium, which was long compared to the pubis.[21] Marguán-Lobon and colleagues, in 2011, argued that this diagnosis is problematic. The large opening in the humerus, although apparently absent in the left humerus, was clearly present in the right humerus of the holotype. Furthermore, their statistical analysis found the specimen to fall well within the continuum of variation of C. sanctus. These authors therefore proposed that C. feducciai is identical (a junior synonym) of C. sanctus.[20]
- Confuciusornis jianchangensis was named in 2010 by Li Li and colleagues, based on specimen PMOL-AB00114 found at Toudaoyingzi. In contrast to most other species, which stem from the Yixian Formation, C. jianchangensis is found in the Jiufotang Formation.[22]
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.[15][23]
Description
Size
Confuciusornis was about the size of a modern crow, with a total length of 50 centimetres (1.6 feet)[24] and 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),[25] or as little as 0.2 kg (0.44 lb).[26] C. feducciai was about a third longer than average specimens of C. sanctus.[21]
Distinguishing traits
Confuciusornis shows a mix of
Skull
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
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
The mandible (lower jaw) is one of the best preserved parts of the skull. It 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 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 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 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.[28][9][29]
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 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.[30] 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 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.[31]
Postcranial skeleton
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 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.[9]
There were at least twelve back vertebrae. They were amphiplatian, flat at both ends, and had rather small
Seven sacral vertebrae were fused into a synsacrum. The front sacral vertebra had a round and concave front articulation facet. The vertebral bodies of 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.[9]
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 the side. Their articulation processes were rather long. The last of these vertebrae had a rectangular profile. Its
Confuciusornis had an exceptionally large
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 the first finger to the contrary was very large and curved.[9] The stub-like third metacarpal, which supported the calami of the feathers, was probably enclosed in the flesh of the hand.[33] The formula of the finger phalanges was 2-3-4-0-0.[9]
The
Feathers and soft tissue
The wing feathers of Confuciusornis were long and modern in appearance. The
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 the hand, but this digit appears to have been free of feathers and independent of the body of the wing in Confuciusornis.[9] 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.[34] 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.[9]
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.[9]
Laser fluorescence of two Confuciusornis specimens revealed additional details of their soft-tissue anatomy. The pro
Plumage pattern
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 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.[35] However, a second research team failed to find these reported traces of pheomelanosomes. Their 2011 study also found 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 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.[36]
A 2018 study of the specimen CUGB P1401 indicated the presence of heavy spotting on the wings, throat, and crest of Confuciusornis.[37]
Classification
Hou assigned Confuciusornis to the Confuciusornithidae 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 an enantiornithean but concluded it was the sister taxon of the Enantiornithes, within a larger Sauriurae.[12] 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.[38] In 2001, Ji Qiang suggested an alternative position as the sister taxon of the Ornithothoraces.[39]
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.[40] Several traits of Confuciusornis show its position in bird evolution; 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.[41] One controversial study concluded that Confuciusornis may be more closely related to Microraptor and other dromaeosaurids than to Archaeopteryx,[42] but this study was criticized on methodological grounds.[citation needed]
The present standard interpretation of the
Aves
|
| ||||||||||||||||||||||||||||||||||||
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.[42][43]
Paleobiology
The large, fleshy
Comparisons between the
Flight
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 a central keel, a strut-like coracoid, a large deltopectoral crest, a strong ulna (forearm bone) and an enlarged second metacarpal.[45] 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 the body, and its relatively smaller sternal keel indicates that it likely was not capable of flight for extended periods of time.[33]
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.[46] 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.[27] 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.[47] 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.[34]
Also a controversy is the strength of the feathers. In 2010, Robert Nudds and
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 is consistent with either birds that live in dense forests or gliding birds; the former is consistent with its environment being densely forested,[49] 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 a straight airfoil. This collectively is strongly indicative that Confuciusornis was capable of powered flight, if not only for short periods of time.[33]
Tail feathers
Many specimens of Confuciusornis preserve a single pair of long, streamer-like tail feathers, similar to those present in some modern birds-of-paradise.[50] Specimens lacking these feathers include ones that otherwise have exquisitely preserved feathers on the rest of the body, indicating that their absence is not simply due to poor preservation.[9] 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.[27] 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.[20] The biological meaning of this pattern has been discussed controversially.[20] Martin and colleagues suggested that 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.[27] This interpretation was followed by the majority of subsequent studies.[51] 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 the sexes.[9]
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
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 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.[9] Peters and Petters, on the other hand, suggested that Confuciusornis may have shed the feathers as 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.[52] 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.[20]
Reproduction
In 2007, Gary Kaiser mentioned 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 the head of the animal; according to Kaiser, it would have fit precisely through the pelvic canal of the bird.
Growth
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
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
The idea of a dinosaur-like mode of growth was criticized by Winfried and Dieter Peters in 2008, who argued that the body size of the smaller size class was too large to possibly have represented the youngest growth state. Analyzing an extended data set, these researchers identified a third size class that supposedly represented this youngest growth state. As it would be highly unlikely that Confuciusornis showed two distinct growth spurts, a feature unseen in known amniotes, they concluded that the two larger size classes represented the two sexes rather than growth stages (sexual size dimorphism). The long tail feathers would have occurred in both sexes, one of which was the largest. This interpretation is consistent with an avian-style mode of growth, as it was suggested by the earlier histological studies. It is also consistent with comparisons to modern birds, in which long tail feathers are typically unrelated to the sexes. The absence of long tail feathers in many specimens was suggested to be the result of stress-induced shedding prior to death.[52]
Chiappe and colleagues defended their findings in a 2010 comment, arguing that the assumed short, avian-like growth period is unlikely. The calculation presented by De Ricqlès in 2003 of a growth phase of less than 20 weeks was based on the assumption that bone diameters grew by 10 µm per day, which is subjective. Rather, histology reveals the presence of different tissue types in the bone that grew at different rates, as well as pauses in growth as indicated by the lines of arrested growth. Thus, growth periods must have been longer than in modern birds and likely took several years, as is true for the modern kiwi.[62][63] The observed size distribution can, therefore, be feasibly explained by assuming a dinosaurian-style growth.[62][64] In an invited reply in 2010, Peters and Peters stated that Chiappe and colleagues did not comment on their main argument, the gap in body size between the smaller size class and inferred hatchlings, which accounts for one order of magnitude and would be most consistent with a sexual size dimorphism.[64] Marugán-Lobón and colleagues studied the relationships between the presence and absence of long tail feathers and the lengths of various long bones of the arms and limbs, using a once more enlarged sample of 130 specimens. While confirming that the tail feathers are unrelated to body size, their presence corresponds to different proportions of the forelimb compared to the hind limb. The authors concluded that the meaning of the observed distributions of both the tail feathers and the body size remains contentious.[20]
Chiappe and colleagues, in their 2008 study, concluded that limb bones growth was almost isometric, meaning that skeletal proportions did not change during growth.[15] This was contested by Peters and Peters in 2009, who observed that wing bones tended to be proportionally longer in very small individuals, as seen in modern chicken, and thus grew allometrically.[52] Chiappe and colleagues, in their 2010 comment, responded that proportional variation is present across the whole size range, and that the presence of allometry was not conclusively demonstrated by the analyses presented by Peters and Peters.[62]
Possible medullary bone
A 2013 histological study by Anusuya Chinsamy and colleagues found
Diet
In 1999, Chinese paleontologist Lianhai Hou and colleagues suggested that Confuciusornis was likely herbivorous, though no stomach contents were yet known, pointing out that the beak curved upwards and was not raptorial.[19] Paleontologists Dieter S. Peters and Ji Qiang hypothesized in 1999 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. Several extant bird species have been presented as modern analogues of Confuciusornis providing insight into its possible lifestyle. 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.[34]
Polish paleontologist
In 2003 Chinese paleontologists Zhonghe Zhou and Fucheng Zhang stated that though nothing was known about its diet, its robust and toothless jaws suggested it could have fed on seeds, and noted Jeholornis preserved direct evidence of such a diet.[67]
In 2006, Johan Dalsätt and colleagues described a C. sanctus specimen (
Andrei Zinoviev assumed it caught fish on the wing.[69]
The skull was relatively 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, as with more basal theropod dinosaurs, and the premaxillae of the snout reaching all the way to the frontals, forcing the nasals to the sides of the snout.[9]
Paleoenvironment and paleoecology
Confuciusornis was discovered in the Yixian and Jiufotang Formations and is a member of the Jehol Biota.[68] Tuff makes up a considerable amount of the rock composition in both due to frequent volcanic eruptions, which were slightly more frequent in the Yixian Formation. Shale and mudstone also are major components of the formations. The tuff has allowed detailed dating of the formations by using 40Ar-39Ar isotopes. This results in an age of approximately 125 to 120 million years ago for the Yixian formation and approximately 120.3 million years ago for the Jiufotang Formation.[13] The fossils were buried as a result of flooding and volcanic debris. This method of preservation resulted in fossils that are very flat, almost two-dimensional.[70] The volcanic strata have allowed the preservation of various soft tissues, such as detailed feather impressions. Using oxygen isotopes in reptile bones found in the formation, a 2010 study determined that many formations from East Asia, including the Yixian, had a cool temperate climate. The mean air temperature of the Yixian Formation was estimated at 10 °C ± 4 °C. Fossils of Xenoxylon, a type of wood known from temperate areas of the time, have been found throughout the region. Additionally, reptiles needing heat, such as crocodilians, are absent.[71]
The majority of Jehol flora has been discovered in the lower Yixian Formation. This flora includes most groups of Mesozoic plants, including
See also
References
- PMID 36543908.
- ^ Ivanov, M., Hrdlickova, S. & Gregorova, R. (2001) The Complete Encyclopedia of Fossils. Rebo Publishers, Netherlands. pp. 312
- .
- S2CID 32369205.
- ^ ISBN 0-520-20094-2.
- ^ a b Zhou, Z. (1995). "The discovery of Early Cretaceous birds in China". Acta Palaeornithologica. 181: 9–22.
- ^ a b Hou, L.; Zhou, Z.; Gu, Y.; Zhang, H. (1995). "Confuciusornis sanctus, a new Late Jurassic sauriurine bird from China". Chinese Science Bulletin. 40 (18): 1545–1551.
- S2CID 4245171.
- ^ a b c d e f g h i j k l m n o p q r s t u Chiappe, Luis M., Shu-An, Ji, Qiang, Ji, Norell, Mark A. (1999) "Anatomy and systematics of the Confuciusornithidae (Theropoda:Aves) from the Late Mesozoic of northeastern China" "Bulletin of the American museum of Natural History no.242 89pp.
- ^ ISBN 978-1-4214-2024-0.
- ^ ISBN 978-0-12-374173-8.
- ^ a b c Zhou, Z; Hou, L. (1998). "Confuciusornis and the early evolution of birds". Vertebrata PalAsiatica. 36 (2): 136–146.
- ^ doi:10.1002/gj.1045.
- ^ PMID 20947746.
- ^ PMID 18832054.
- ^ Wang X, Zhang F, Xu X, Wang Y, Gu G (2000). "Taphonomy and mass mortality of Confuciusornis and feathered dinosaurs at the Sihetun and Zhangjiagou sites in western Liaoning, China". Vertebrata PalAsiatica. 38 (supp): 32.
- ^ a b Hou, L. (1997). Mesozoic Birds of China (PDF) (in Chinese). Translated by Downs, W. Phoenix Valley Provincial Aviary of Taiwan.[pages needed]
- ^ S2CID 84976296.
- ^ S2CID 4402195.
- ^ S2CID 85269014.
- ^ S2CID 21418230.
- ^ Li, L. (2010). "[Chinese] [A new species of Confuciusornis from Lower Cretaceous of Jianchung, Liaoning, China]". Global Geology. 29 (2): 183–187.
- .
- ISBN 978-0-375-82419-7.
- ^ S2CID 12340187.
- ^ PMID 20947747.
- ^ S2CID 10934480.
- ^ S2CID 90118265.
- ^ ISBN 978-0-520-20094-4.
- .
- S2CID 221713024.
- ^ Senter, P. (2006). "Scapular orientation in theropods and basal birds, and the origin of flapping flight" (PDF). Acta Palaeontologica Polonica. 51 (2): 305–313. Archived from the original (PDF) on 2007-06-26. Retrieved 2006-08-22.
- ^ PMID 27973609.
- ^ S2CID 9489758.
- S2CID 205219587.
- S2CID 206534048.
- PMID 30405969.
- .
- ^ Ji, Q. (2001). "[Chinese] "New advances in the study of the primitive bird Confuciusornis". Geological Science and Technology Information. 20: 30–34.
- ^ L. M. Chiappe (2002) "Basal bird phylogeny: problems and solutions". In: L. M. Chiappe and L. M. Witmer (eds.), Mesozoic Birds: Above the Heads of Dinosaurs. University of California Press, Berkeley pp. 448–472
- ^ Clarke,,Julia. A., Norell, Mark. A. (2002) "The Morphology and Phylogenetic Position of Apsaravis ukhaana from the Late Cretaceous of Mongolia". American Museum Novitates, No. 3387, American Museum of Natural History, New York, NY 10024.
- ^ PMID 16533313.
- S2CID 196607241.
- S2CID 33253407.
- ^ Zhou Z. and Farlow, J.O. (2001) "Flight capability and habits of Confuciusornis". In: Gauthier and Gall (eds). New perspectives on the origin and early evolution of birds: proceedings of the international symposium in honor of John H. Ostrom. Peabody Museum of Natural History. Yale University, New Haven. pp. 237–254
- ^ "Senter, 2006 by Felipe Elias - Issuu". issuu.com. 24 January 2010. Retrieved 2022-03-25.
- .
- .
- S2CID 4412725.
- PMID 22954658.
- ^ PMID 23340421.
- ^ PMID 19776067.
- ^ ISBN 978-0-7748-1344-0.
- ^ .
- S2CID 3588317.
- .
- ^ a b Zhang, F.; Hou, L.; Ouyang, L. (1998). "Osteological microstructure of Confuciusornis: preliminary report". Vertebrata PalAsiatica. 36: 126–135.
- ^ Zhang, F.-C.; Xu, X.; Lü, J.; Ouyang, L. (1999). "Some microstructure difference among Confuciusornis, Alligator and a small theropod dinosaur, and its implications". Paleoworld: 296–308.
- S2CID 4331331.
- S2CID 4335246.
- ^ S2CID 84936431.
- ^ PMID 20236961.
- PMID 19515655.
- ^ PMC 2936223.
- PMID 30518763.
- ^ Elzanowski, A. (2002) "Biology of basal birds and the origin of avian flight". In: Zhou Z., Zhang F. (eds) Proceedings of the 5th Symposium of the Society of Avian Paleontology and Evolution, Beijing, 1–4 June 2000. Science, Beijing, pp 211–226
- doi:10.1139/e03-011.
- ^ S2CID 14377499.
- S2CID 85359766.
- ^ .
- PMID 21393569.
- S2CID 206537426.
- PMID 27641767.
- PMID 29107548.
- PMID 22952855.
- S2CID 29689629. Archived from the original(PDF) on 17 April 2012.
External links
- Well preserved fossil attributed to Confuciusornis from the Jiufotang Formation