Yanornithiformes is an

order Order, ORDER or Orders may refer to: * A socio-political or established or existing order, e.g. World order, Ancien Regime, Pax Britannica * Categorization, the process in which ideas and objects are recognized, differentiated, and understood ...

of ornithuromorph

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic Geological period, period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the #Evolutio ...

s from the early

Cretaceous Period The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 77.1 million years, it is the ninth and longest geologi ...

China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...

. All known specimens come from the

Yixian Formation The Yixian Formation (; formerly Romanization of Chinese, transcribed as Yihsien Formation or Yixiang Formation) is a geological formation in Jinzhou, Liaoning, People's Republic of China, that spans the Barremian stage of the Early Cretaceous. I ...

and

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 (see Jehol Biota). It is a member of the Jehol group. T ...

, dating to the early

Aptian The Aptian is an age (geology), age in the geologic timescale or a stage (stratigraphy), stage in the stratigraphic column. It is a subdivision of the Early Cretaceous, Early or Lower Cretaceous epoch (geology), Epoch or series (stratigraphy), S ...

age, 124.6 to 120 million years ago. The family Songlingornithidae was first named by Hou in 1997 to contain the type genus, '' Songlingornis''.Hou, (1997). ''Mesozoic Birds of China''. Taiwan Provincial Feng Huang Ku Bird Park. Taiwan: Nan Tou. 228 pp. Clarke et al. (2006) was first to find a close relationship between ''Songlingornis'' and the "yanornithids", which had been previously named to contain the similar species ''Yanornis'' and ''Yixianornis''. At least one study has found '' Hollanda'' from the Late Cretaceous of Mongolia to be a member of this group. The family Yanornithidae (now Songlingornithidae) had been placed in its own order containing no other families, named Yanornithiformes, in 2001.Clarke, Zhou and Zhang, (2006). "Insight into the evolution of avian flight from a new clade of Early Cretaceous ornithurines from China and the morphology of ''Yixianornis grabaui''." ''Journal of Anatomy'', 208: 287-308. Beginning in 2012, multiple studies began to recover the songlingornithids in a clade with the hongshanornithids, a group of smaller, more specialized ornithuromorphs from the same time and place as some of the songlingornithids.O'Connor, J.K. and Zhou Z. (2012). "A redescription of ''Chaoyangia beishanensis'' (Aves) and a comprehensive phylogeny of Mesozoic birds." ''Journal of Systematic Palaeontology'', (advance online publication). Other studies however continued to place the hongshanornithids just outside the yanornithiform clade.

References

Euornithes Bird clades Dinosaurs of China {{Paleo-bird-stub