Yanornithiformes is an

order Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of ...

of ornithuromorph

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 from the early

Cretaceous Period The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of t ...

China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's List of countries and dependencies by population, most populous country, with a Population of China, population exceeding 1.4 billion, slig ...

. All known specimens come from 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 ...

and

Jiufotang Formation The Jiufotang Formation ( Chinese: 九佛堂组, pinyin: ''jiǔfótáng zǔ'') is an Early Cretaceous geological formation in Chaoyang, Liaoning which has yielded fossils of feathered dinosaurs, primitive birds, pterosaurs, and other organisms (see ...

, dating to the early

Aptian The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous Epoch or Series and encompasses the time from 121.4 ± 1.0 Ma to 113.0 ± 1.0 Ma (million years ag ...

age, 124.6 to 120 million years ago. The family Songlingornithidae was first named by Hou in 1997 to contain the type genus, ''

Songlingornis ''Songlingornis'' is a prehistoric bird genus from the Early Cretaceous. Its fossils have been found in the Jiufotang Formation of Liaoning (PRC). The age of these rocks is somewhat disputed, but probably around the early Aptian, 125-120 milli ...

''.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 the late Cretaceous Mongolian bird '' Hollanda'' to be a member of this group. The family Yanornithidae (now

Songlingornithidae Songlingornithidae is a family of basal euornitheans from the Early Cretaceous of China. All known specimens come from the Jiufotang Formation and the Yixian Formation, dating to the early Barremian and Aptian ages, 125–120 million years a ...

) 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, several studies began to find that the hongshanornithids, smaller, more specialized birds from the same time and place as some of the songlingornithids, were more closely related to songlingornithids than to other early birds, making them part of the same clade,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). while some studies continued to find them just outside the yanonrithiform clade.

References

Prehistoric euornitheans Early Cretaceous birds of Asia Aptian first appearances Early Cretaceous extinctions {{paleo-bird-stub