''Jixiangornis'' is a genus of basal

avialans Avialae ("bird wings") is a clade containing the only living dinosaurs, the birds. It is usually defined as all theropod dinosaurs more closely related to birds (Aves) than to deinonychosaurs, though alternative definitions are occasionally use ...

from the Early Cretaceous. Like later avialans, it had no teeth, but it also had a long tail, unlike modern

bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...

s. Since teeth were still present in some more derived short-tailed avialans, ''Jixiangornis'' seems to have evolved its toothlessness independently of modern birds. The long forelimb (131% of hindlimb length) indicates at least some aerial ability. ''Jixiangornis'' is currently known only from a single specimen, a complete but juvenile skeleton. The fossil was found in the

Yixian Formation The Yixian Formation (; formerly transcribed as Yihsien Formation) is a geological formation in Jinzhou, Liaoning, People's Republic of China, that spans the late Barremian and early Aptian stages of the Early Cretaceous. It is known for its exq ...

near Beipiao City, western Liaoning, China.

Classification

The only known species, ''J. orientalis'' ("Oriental bird from the Yixian Formation"), was described in November 2002. Ji ''et al.'' (2002) considered ''Jixiangornis'' capable of stronger flight than either '' Archaeopteryx'' or ''

Jeholornis ''Jeholornis'' (meaning "Jehol bird") is a genus of avialans that lived between approximately 122 and 120 million years ago during the early Cretaceous Period in China. Fossil ''Jeholornis'' were first discovered in the Jiufotang Formation in ...

''. Their phylogenetic tree shows ''Jixiangornis'' forming a clade (called "Euavialae" by Ji ''et al.'') with birds that excludes ''Archaeopteryx'' and ''Jeholornis'' (=''Shenzhouraptor''). An alternative view was presented by Zhou Zong-He and Zhang Fu-Cheng in 2006. They classified both ''Jixiangornis'' and ''Shenzhouraptor'' as junior synonyms of ''

Jeholornis prima ''Jeholornis'' (meaning "Jehol bird") is a genus of avialans that lived between approximately 122 and 120 million years ago during the early Cretaceous Period in China. Fossil ''Jeholornis'' were first discovered in the Jiufotang Formation in H ...

'', meaning that ''Jixiangornis'' cannot be more advanced than ''Shenzhouraptor''. This approach, however, was problematical given the numerous differences between ''Jixiangornis'' and ''Shenzhouraptor/Jeholornis'', and a phylogenetic analysis performed in 2014 found that it may actually be more closely related to short-tailed avialans (

Pygostylia Pygostylia is a group of avialans which includes the Confuciusornithidae and all of the more advanced species, the Ornithothoraces. Definition The group Pygostylia was intended to encompass all avialans with a short, stubby tail, as opposed to ...

) than to ''Jeholornis'', as originally thought. Hartman ''et al''. (2019), Cau (2020) and Wang ''et al'' (2020) found ''Jixiangornis'' to have been a jeholornithid but not a synonym of ''Jeholornis''.

References

Sources

* * Zhou, Z.-H. & Zhang, F.-C. (2006): Mesozoic birds of China - A synoptic review. ''Vertebrata PalAsiatica'' 44(1): 74–98
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Early Cretaceous birds of Asia Fossil taxa described in 2002 Jiufotang fauna Prehistoric avialans Yixian fauna {{paleo-bird-stub