Jeholornithidae

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. Fossil Jeholornis were first discovered in the Jiufotang Formation in Hebei Province, China (in what was previously Rehe Province, also known as Jehol—hence the name) and additional specimens have been found in the older Yixian Formation.

Jeholornithidae is a family of avialan theropods whose taxonomy is controversial, whose remains are found in fossil deposits of what is now China. The controversy stems from whether most of the taxa in the group are just specimens of Jeholornis, as well as if the group is monophyletic at all. In the description of Kompsornis the authors Wang et al. (2020) found moderate support in the monophyly of the group, placing them as basal avialans and sister to Pygostylia. No phylogenetic definitions for these groups were provided by Zhou and Zhang, but a topological definition was provided in 2020 by

Kompsornis (meaning "elegant bird") is an extinct genus of avialan dinosaurs that lived during the Early Cretaceous period of China. The type and only known species is Kompsornis longicaudus; the specific name means "long-tailed". It is known from only a single fossil specimen from the Jiufotang Formation. Kompsornis was closely related to the well-known Jeholornis, another long-tailed avialan from China, but differs from it in features of its skeleton, particularly the fusion and growth rate of its bones. Like other jeholornithiforms, Kompsornis was a long-tailed avialan with long wings and p