Jeholornis (meaning "Jehol bird") is a genus of avialan dinosaurs that lived between approximately 122 and 120 million years ago during the early Cretaceous Period in China.

[1] Jeholornis had long tails and few small teeth, and were approximately the size of turkeys,[2] making them among the largest avialans known until the Late Cretaceous.

Jeholornis were relatively large, basal avialans, with a maximum adult length of up to 75 cm (2.5 ft) and an estimated weight of 2.27-9.1 kg (5-20 lbs).

[4] Their arms were robust and longer than the legs, with relatively well-developed shoulder girdles indicating strong wing musculature.

A study by Gregory M. Erickson in 2009 has shown that Jeholornis (along with Archaeopteryx) had relatively slow ontogenic development, i.e. they grew very slowly, compared to most modern birds, which grow very quickly.

The first specimen shows that the flight feathers were asymmetrical (and therefore aerodynamic, as in modern flying birds) and up to 21 centimeters long, longer than the forearm and hand combined.

A second specimen is in the collection of the Liaoning Provincial Museum of Paleontology, and is catalogued as LPM 0193 it was reported as a new species, Shenzhouraptor sinensis, in the journal The Geological Bulletin of China in 2002, but is likely a junior synonym of Jeholornis prima.

Two of the diagnostic characteristics which could have distinguished Shenzhouraptor from Jeholornis were its smaller size and the absence of teeth, which may be attributed to age and preservational bias.

[8] The discovery of Shenzhouraptor was reported in at least one newspaper on July 23, 2002,[17] though the official paper naming the species, published in a monthly journal, did not bear a specific date of issue.

This examination concluded that Shenzhouraptor was a valid species distinct from Jeholornis prima and other jeholornithiforms, rejecting the suggestion that they are synonymous.

A phylogenetic analysis supported this conclusion, recovering Shenzhouraptor as a less derived species outside of a clade composed of Jeholornis prima, J. curvipes and Kompsornis.

Some birds like Jeholornis evolved the ability to eat the fruits and a co-evolutionary relationship started about 120 million years ago.

The flight apparatus of the Jeholornis was overall quite similar to that of Confuciusornis in form and function, with forelimbs longer than hindlimbs, and a short, robust hand.

[5] However, like other basal (non-ornithothoracean) avialans and theropod dinosaurs, the shoulder blades of Jeholornis were oriented along the sides of the body, rather than on top of its back.

Primitive avialans like Archaeopteryx, Confuciusornis, and Jeholornis would not have been able to lift their arms vertically to achieve true flapping flight, though semi-powered gliding or parachuting would have been possible.

In a 2008 presentation for the conference of the Society of Avian Paleontology and Evolution (SAPE), Zhiheng Li and Yuguang Zhang re-examined the evidence for a reversed hallux in Jeholornis.